???? ????? ?? (Introduction to Linear by 94e1A6

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									 한국과학기술원 산학협동공개강좌 : 전자 패키징의 신뢰성 평가 및 설계 기술




       파괴역학적 기법 소개 및 응용

           I. 파괴역학(균질재료 및 계면재료)의 소개
                    II. 파괴인성치(접착력) 측정법
                            III. 파괴역학적 계산
    IV. 전자패키지의 파손사례 및 파괴역학의 응용사례


                        한국과학기술원 기계공학과
                                   엄윤용 교수


Computer Aided Reliability Evaluation Lab.   1 / 74
                      I. 파괴역학의 소개

(Introduction to Fracture Mechanics)




 Computer Aided Reliability Evaluation Lab.   2 / 74
                                          Design criteria

   Stress approach                                      Fracture mechanics approach
        Not consistent                                       Consistent
        Hardly applied to complex                            Easily applied even to complex
         structures                                            structure


                                                              
                             u                                             K I  K IC


                    σ : applied stress                                K I : stress intensity factor
                    σ u : ultimate stregth                            K IC : fracture toughness
                                                              

         Computer Aided Reliability Evaluation Lab.                                        3 / 74
                                           Fracture modes


  Mode I                                  Mode II             Mode III
(opening mode)                         (in-plane shear)      (out-of-plane shear)


 yy


                                   xy
                                                           yz
                                                                             yz
     yy                         xy

       Computer Aided Reliability Evaluation Lab.                                  4 / 74
                      Stress field near the crack tip

   Stress at the crack tip

                                             xx                1  sin 2sin3 2
                                                    KI                               
                                             yy       cos 21  sin 2sin3 2
                                                   2r          sin 2cos3 2 
                                             xy                                      

                                             xx           sin  2 2  cos 2 cos3 2
                                                     K II                                      
                                             y y         sin  2 cos 2  cos3 2  
                                                       2r 
                                                             cos 2 1  sin  2sin 3 2  
                                                                                               
                                             xy 



                                                   K I : Mode I stress intensity factor
                                                   
                                                   K II : Mode II stress intensity factor


      Computer Aided Reliability Evaluation Lab.                                                 5 / 74
                                 Energy release rate

   Energy release rate, G


        
G        ,   U-W
        a

    : Mechanical potential energy
   U : Strain energy stored in the body
   W : Work done by external forces


Mechanical potential energy
= Strain energy stored in the body
- Work done by external forces


     Computer Aided Reliability Evaluation Lab.        6 / 74
                                 Energy release rate vs.
                                  stress intensity factor

    Stress intensity factor                             Energy release rate

                                                               
                                                           G 
                                                                a
                                                              K2 K2 K2
                                                              I  II  III
                                       r                      E E 2

         KI          K II         K
 yy        , xy       ,  yz  III
         2r         2r           2r                             E
                                                                            : Plane stress
                                                             E   E
                                                                  1   2   : Plane strain
                                                                  
KI, KII, KIII : Stress intensity factors



         Computer Aided Reliability Evaluation Lab.                                           7 / 74
                     Plastic effect on crack tip


       
                                                                                             2
                                                                                 1  KI 
                                                                                    
                                                 Yielding zone size :    ry 
                                                                                2   y 
                                             
                                                                                    

                                                Plastic zone size
                                                                     2
                                                            1  KI 
                                                  rp  2ry    for plane stress
               ry rp                r                         y 
                                                               
                                                                       2
                                                             1 K 
                                                  rp  2ry   I  for plane strain
                                                            3   y 
                                                                

• Ductile fracture : sufficient plastic deformation before fracture
• Brittle fracture : small plastic deformation before fracture

Computer Aided Reliability Evaluation Lab.                                          8 / 74
                                       Fracture criterion

    Stress intensity factor                             Energy release rate


      K I  K IC        : Crack propagates!                G  Gc        : Crack propagates!


KI : SIF (Calculated value)                                G : Energy release rate
KIC : Fracture toughness (Material property)               Gc : Critical energy release rate


                                 KI                        Gc = 2gDa (surface energy)
                         yy                                 + (plastic dissipation energy)
                                 2 r
                                                              + (thermal energy)
                                                              + (sound energy)
                                                              +…
                                   r
         Computer Aided Reliability Evaluation Lab.                                            9 / 74
                                        SIF for simple geometry

            Finite crack in infinite body                           Surface crack in finite-width
             under uniform tension                                    plate under uniform tension

                                                                                                                    a
                                                                                          K I   af ();  
                                                                                                                      c

                                                                                                  
                                   K I   a
                                                                                                           f()
                                                                                               0(c)      1.12
                                                                  a
                                                                                                 0.2       1.37
                                                                          c
                                                                                                 0.4       2.11

                                                                                               0.5       2.83



   Ref. H. Tada, P. Paris, and G. Irwin, 1985, “The Stress Analysis of Cracks Handbook,” 2nd ed., St. Louis, Missouri.
         G.C. Sih, 1973, “Handbook of Stress Intensity Factors,” Lehigh University, Bethlehem, Pennsylvania.


                Computer Aided Reliability Evaluation Lab.                                                        10 / 74
                                  Mixed type loading

   Mixed loading on crack tip                       Crack trajectory


                          yy                                         yy


              2a
                           b




                          yy                                         yy

     Computer Aided Reliability Evaluation Lab.                             11 / 74
                     Interfacial fracture mechanics



   Energy release rate and stress intensity factor

                                                           1 1 1     1 
      G
                  1
                            K 2  K 2           wher e          E E 
                                                                      
            E* cosh 2  
                               I     II                      *
                                                           E    2 1   2 




   Criterion for crack propagation

                                                K II 
            G  Gc                          K 
                                 where   tan     1
                                                      
                                                I


     Computer Aided Reliability Evaluation Lab.                              12 / 74
  II. 파괴인성치(접착력) 측정법

    (Measurement of Fracture
          Toughness)



Computer Aided Reliability Evaluation Lab.   13 / 74
                  ASTM Standard for fracture mechanics


   E616-89 : Terminology Relating to Fracture Testing
   E338-91 : Standard Test Method for Sharp-Notch Tension Testing for High-Strength Sheet Materials
   E399-90 : Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials
   E561-94 : Practice for R-Curve Determination
   E813-89 : Standard Test Method for JIC, A Measure of Fracture Toughness
   E1152-87 : Standard Test Method for Determining J-R Curve
   E1304-89 : Standard Test Method for Plane-Strain (Chevron-Notch) Fracture Toughness of Metallic Materials
   E1290-93 : Standard Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness
    Measurement
   E1150-87 : Definition of Terms Relating to Fatigue
   E647-93 : Standard Test Method for Measurement of Fatigue Crack Growth Rate
   D5045-91a : Standard Test Method for Plane-Strain Fracture Toughness and Strain Energy Release Rate of
    Plastic Materials




           Computer Aided Reliability Evaluation Lab.                                                  14 / 74
                                Preparation of specimen

   Standard : ASTM-E399, D5045                          Calculation
    Specimen : Compact Tension (CT)                                       PQ
                                                           K IC  f x 
                                                                         BW1/ 2
                                                           KIC : Fracture toughness
        0.25W                                              PQ : Critical load

                                           0.6W            f(x) = 8.34       at x=0.45
0.275W
                                                                  9.66       at x=0.50
                                                                  11.35      at x=0.55
                                                          x=a/W, (0.45 < x < 0.55)
                 a
                      W             B                                              2
                                                                       K 
                                                              B,a  2.5 IC 
                                                                        
                                                                        yield 
         Computer Aided Reliability Evaluation Lab.                                      15 / 74
           Variation of KC with specimen thickness




Computer Aided Reliability Evaluation Lab.           16 / 74
                 What is adhesion?




Computer Aided Reliability Evaluation Lab.   17 / 74
                                    Adhesion의 구분

   Practical Adhesion

       Adhesion test에서 측정되는 힘이나 에너지.
       300 가지가 넘는 측정방법으로 측정되는 adhesion은 모두 practical
        adhesion.
       Practical Adhesion = f ( fundamental adhesion , other factors )
          Film의 stress, film thickness, substrate 물성치, plastic deformation,
            viscous dissipation, failure mode, applying force mode 등 모든 실험
            변수들이 other factors.
       실험방법에 따라 adhesion 을 나타내는 단위가 다르며 의미하는 특성
        또한 다르다.




    Computer Aided Reliability Evaluation Lab.                                 18 / 74
                            Adhesion measurement

   Adhesion 측정에 따른 일반적인 문제점

       주변 환경, 조건에 따라 adhesion의 차이가 발생
        : 온도 변화, 제품 사용환경, 보관 상태, 보관 시간 등
       Adhesion의 정의 문제
        : 관찰 수단의 resolution의 level
       Testing Method
        : Testing method 결과 상호간의 관계가 불분명함
       시편
        : 측정에 사용되는 시편이 제품을 얼마나 반영할 수 있는가.
       Undetected residual stresses


    Computer Aided Reliability Evaluation Lab.     19 / 74
                                 Testing method의 선택

   기본적인 고려사항                                            이론적 해석

       제품의 실제 사용 환경과 형태                                     많은 수의 adhesion testing
       Testing method 에 따라 결과의                               method는 이론적인 해석이
        단위나 경향이 다르며, 또한                                       불가능하고 결과 자체가
        각각이 특징적으로 제공할 수                                       numerical value를 주지 않는
        있는 정보의 범위와 종류도 다름                                     방법도 많다.

       실험환경이 사용환경을 얼마나                                      Fracture mechanics를 통한
        잘 반영했는가 하는 것이 중요                                      측정과 해석은 이론적으로
                                                              상당히 잘 정립되어 있는 편이다.




         Computer Aided Reliability Evaluation Lab.                                    20 / 74
              Testing method 1 : Scratch test




                                                Force 측정
                                                Adhesion의 quality를 판단
                                                적용 Film의 두께
                                                 : 수십 mm ~ 수 mm
                                                비교적 좁은 범위의 영역 측정


Scratch test


Computer Aided Reliability Evaluation Lab.                               21 / 74
           Testing method 2 : Indentation test


                                             Force 측정
                                             Shear strength, resistance to interfacial
                                              failure
                                             실험 시 발생하는 strain, stress 계산
                                             적용 film의 두께
                                              : 수 mm ~ 수백 mm
                                               (nano-indentation의 경우 수 m )
                                             Interfacial fracture toughness
                                              측정가능 (quantity 측정)
Indentation test
                                             매우 좁은 영역에 대한 측정

 Computer Aided Reliability Evaluation Lab.                                        22 / 74
              Testing method 3 : Peeling test




                                                Peeling energy 측정
                                                Bending energy 가 포함되어
                                                 측정 (quality 평가)




  Peeling test


Computer Aided Reliability Evaluation Lab.                               23 / 74
              Testing method 4 : Pull-off test




                                                Force/area 측정
                                                실험 변수들의 제어가 비교적
                                                 어려운 편
                                                비교적 넓은 범위의 영역에
                                                 대한 측정


   Pull-off Test



Computer Aided Reliability Evaluation Lab.                        24 / 74
               Testing method 5 : Blister test




                                                Pressure 측정
                                                Soft film on hard substrate 에
                                                 적용되는 한계
                                                Interfacial fracture toughness
                                                 측정 가능


   Blister test



Computer Aided Reliability Evaluation Lab.                                   25 / 74
                             Measurement of
                      interfacial fracture toughness

   하중실험                                             변위실험

                         P                                         Static Load
     Crack

                                                                 Specimen
Fixture                                                Step Motor
                                                      (displacement)
                                                                                 Grip
                                Specimen
                        P


     Ref. 이경우, 임지혁, 이혁, 엄윤용, 1995, "리드프레임과 에폭시수지 사이의
      계면파괴인성치 측정," 대한기계학회 95년 추계학술대회논문집(I), pp.145-150.


     Computer Aided Reliability Evaluation Lab.                                     26 / 74
                                  Measurement of
                           interfacial fracture toughness
     시편 제작                                                시험기 구성

                                                                     stepping motor
                                                                     harmonic drive
Silver Deposition
                                         Adhesive                    ball screw
                                                                     linear guide


                                        Silicon wafer
                                                                     load cell


                                                                     loading rod
   Adhesive(0.03~0.045mm)         Die Pad(0.15mm)
                                                                           precision
                                                                           translation stage
Silver Deposition                                                    linear encoder
                            Silicon(0.725mm)                         specimen
          Computer Aided Reliability Evaluation Lab.                                27 / 74
                          Interfacial fracture toughness curve


           700                                                        패키지 내의 취약계면 중
           600                        Temperature = 25oC               하나인 리드프레임/접착제
                                         ^ = 40 m
                                          r                            계면의 파괴인성치를 측정.
           500
Gc(J/m2)




                                                                      측정된 계면파괴인성치는
           400
                                                                       하중 모드에의 의존성을 보임.
           300
                                                                      측정된 결과는 패키지 신뢰성
           200
                                                                       평가에 이용될 수 있음.
           100
            0                                                                  Chip
                 -60     -40       -20        0        20     40
                                  Phase angle

            Interfacial toughness between L/F and adhesive

                                                                         EMC    L/F   Adhesive
                 Computer Aided Reliability Evaluation Lab.                           28 / 74
         Interfacial fracture toughness curve

                                       40



                  Fracture Toughness
                                                            변위실험
                                       30                   하중실험

                       Gc [kN/m]
                                       20


                                       10


                                        0

                                            -60 -40 -20 0   20 40 60
                                             Y (phase angle) [degree]

                                        (Leadframe/EMC)

Computer Aided Reliability Evaluation Lab.                              29 / 74
                             Measurement of
                      interfacial fracture toughness

   Blistering 및 Moire 방법


thin film                                                   Screen

silicon                                                    Pin Hole
chip
              Pressure                                   Lens
                                                                 Diffuser
                                                                              Moire fringe on thin film

                         Specimen


                                                                      Light Source


                        Grating          Beam Splitter


     Ref. 김재현, 문호정, 엄윤용, 1996, "모아레 방법을 이용한 박막의 기계적 성질
      측정에 관한 연구," 대한기계학회 춘계학술대회논문집(I), pp.19-24

     Computer Aided Reliability Evaluation Lab.                                                 30 / 74
                            Measurement of
                     interfacial fracture toughness

   굽힘실험                                            Blade 방법

    P                     P




                        precrack




    Computer Aided Reliability Evaluation Lab.                  31 / 74
                 III. 파괴역학적 계산

(Fracture Mechanics Calculation)




 Computer Aided Reliability Evaluation Lab.   32 / 74
                                             J-integral

   Definition                                        Properties
                                                           Conservation integral
                                                           Path independency
                           u i
    J   wdy  ijn j         dS                        Physical meaning of energy
         
                           x1                              release rate, G


      w : strain energy                                                         n
       : integration path
      n : normal vector to                             crack                       




      Computer Aided Reliability Evaluation Lab.                                         33 / 74
                           J-integral using with FEM


(a) Whole mesh                                     D/A     Chip
                                      EMC

                                                                           (h)


                      Leadframe
                                                          crack (a)
(b) Crack tip mesh                                                        crack tip
                                                                      C
                                                                      L
                                                   Leadframe

                          Crack
                                                    EMC


      Computer Aided Reliability Evaluation Lab.                             34 / 74
                         Convergence of J-integral

   Integration path
                                                     J-integral at each path

                                                           PATH   J - INTEGRAL [N/mm]

                                                             1        0.2486E-02
                                                             2        0.2443E-02
                                Leadframe                    3        0.2434E-02
                                                             4        0.2432E-02
                                                             5        0.2430E-02

                 1 2 . . . . 8
                                                             6        0.2430E-02
                                                             7        0.2429E-02
Crack                                                        8        0.2429E-02

                                                     J-integral usage in ABAQUS
                                   EMC                   contour integral,contours=8
                                                         tip,1,0
                                                      tip node      nx, ny (crack direction)

     Computer Aided Reliability Evaluation Lab.                                        35 / 74
            IV. 전자 패키지의 파손사례
              및 파괴역학의 응용사례

(Failure examples of electronic packages
 and applications of fracture mechanics)



   Computer Aided Reliability Evaluation Lab.   36 / 74
                국외 기술 동향 (해외 연구 기관)


       미국 반도체산업협회                                미국 조지아공대
           (SIA)                                    (PRC)
    반도체 및 관련 패키지의 향후                         전자패키지 제조 전반의 신뢰성
    기술 전망 제시                                 연구의 선도적 역할



        미국 뉴욕주립대학                                싱가폴 진틱기술원
           (IEEC)                                  (GINTIC)
   MEMS 및 광소자 패키지 관련                         플립칩의 공정 개발 및 열적/
   신뢰성 연구                                    기계적 신뢰성 연구




     미국 메릴랜드 대학 (CALCE)                            미국 IBM
    전자패키지 분야의 세계적 전자                         기존의 중/대형 컴퓨터 및 PC
    제품 회원사를 확보하여 기계적                         시장을 기반으로 자사 내의 기술
    신뢰성 평가기술을 패키지 분야                         축적을 바탕으로 한 차세대 패키
    에 적용                                     지에 대한 내구성 평가



Computer Aided Reliability Evaluation Lab.                 37 / 74
                                         Die cracking


   Flip Chip BGA




                                                        Chip

                                                        PCB


       Chip과 Substrate간의 Global CTE Mismatch로 인해 발생

     Computer Aided Reliability Evaluation Lab.                38 / 74
                                         Die cracking

   Leadframe Package                     Eject Pin의 위치




                   Chip        EMC
                      b


                  금형


                           Eject Pin


                                                     SAT 사진

       EMC 성형공정에서 eject pin이 올라오면서 package를 금형으로부터
        이형시킬 때 발생.
       원인은 성형공정이 진행되면서 이형력이 증가하기 때문임.


     Computer Aided Reliability Evaluation Lab.               39 / 74
             Via hole delamination, via barrel crack,
                        and pattern crack

   Temperature cycling 환경 하에서 발생된 Organic substrate 내부의 Via
    hole delamination, Via barrel crack
                                             Via Land Crack




                                                    Via Barrel Crack




   Temperature cycling 환경 하에서 발생된 Organic substrate의 Pattern crack




       Computer Aided Reliability Evaluation Lab.                      40 / 74
                                Wire broken failure

   Temperature cycling 환경 하에서 WBGA Package의
    Encapsulant가 수축, 팽창함으로 인해 Wire가 끊어진 불량

                                                      PI Tape   Solder Ball

                                                 Gold Wire                    PSR




                                                                     Elastomer
                                                     Chip
                                                                   Encapsulant

    Computer Aided Reliability Evaluation Lab.                                      41 / 74
                 Wire heel crack 및 Beamlead 불량

   Temperature cycling 환경 하에                        Temperature cycling 환경
    있는 Cu Leadframe적용                                 하에서 BGA의 Beamlead
    Package 의 Wire Stitch                             불량
    Bonding 부위에서 발생된                                      Encapsulant의 반복적인
    Wire heel crack.                                      수축, 팽창과 Bonding Tool
                                                          Damage가 원인




     Computer Aided Reliability Evaluation Lab.                                  42 / 74
                                       Package crack


   Precondition test시 박리 및 Package 외관 균열 발생




     Computer Aided Reliability Evaluation Lab.        43 / 74
                                             계면 박리


   Precondition test에서 Swelling에 의한 계면박리 불량




     Computer Aided Reliability Evaluation Lab.      44 / 74
                                   Passivation Crack


   LOC tape과 EMC간의 박리가
    발생되면서 Passivation
    crack까지 진전됨




     Computer Aided Reliability Evaluation Lab.        45 / 74
                                   Passivation Crack


   Filler damage에 의한
    Passivation crack




     Computer Aided Reliability Evaluation Lab.        46 / 74
                                     Solder joint 불량


   WBGA package에서의 Solder joint 불량
       Package와 PCB board간의 CTE mismatch로 인함.




     Computer Aided Reliability Evaluation Lab.        47 / 74
                                      Solder joint 불량


   Direction of forces and moments
    applied to TSOP depending on
    warpage type
                                                   Warpage로 인해 발생되는 Moment가 인장
                                                   응력성분을 야기시킴

            Cap-type warpage (Pad up)



                                                    Moment가 압축응력성분을 야기시킴


          Cup-type warpage (Pad down)


      Computer Aided Reliability Evaluation Lab.                        48 / 74
       HTS test에서의 Kirkendall void로 인한
                    불량




  168 hr IMC층 성장                   300 hr K/Void 진전   500 hr IMC층 분리




   IMC층 계면균열                          Pad 부위사진         Ball 부위사진


Computer Aided Reliability Evaluation Lab.                             49 / 74
                             패키지 파손의 원인과 형태

   Stress drivers                                    Failure mechanism
        Temperature                                       Fatigue
        Vibration/shock/static loads                      Fracture
        Moisture                                          Diffusion

   Failure sites                                          Corrosion

        Leadless                                     Attach characterization
        J and gull leaded                                 Solders
        Pin grid arrays/Insertion mount                   Conductive adhesives
        Ball grid arrays/CSP                              Underfills
        Flip chip




      Computer Aided Reliability Evaluation Lab.                                   50 / 74
                         팝콘 균열 해석

                ( Popcorn Cracking )




Computer Aided Reliability Evaluation Lab.   51 / 74
                                      연구배경 및 목적

                                                      패키지균열의 메카니즘
   반도체패키지의 경박 단소화에                                       Pre-conditioning
    따라 기계적 신뢰성 요구
   열응력과 고온에서의
    수증기압에 의한 계면박리와
    패키지균열 문제
                                                                   moisture uptake
   열응력과 수증기압의 정량화와
    주요인자의 파악                                              Reflow soldering
   차세대 반도체 개발을 위한
    신뢰성 평가방법 확립

                                                                 pressure generation
      Computer Aided Reliability Evaluation Lab.                                       52 / 74
                               Concentration distribution
                                  at pre-conditioning

   Model                                                 Governing equation, B.C. and I.C.

                                                                C       2C
                                                                   D 2,
                                                                t      x
                                                                C  0,att  0
                                                                C
                                                                    0,atx  0
      h                                                         x
                     x                                          C    Ps  Satx  h

                      a                                   Method
Area of analysis                                               FDM(Finite Difference Method)




          Computer Aided Reliability Evaluation Lab.                                      53 / 74
                                        Concentration distribution
                                           at pre-conditioning

   Typical concentration distribution

                    0.005
                                                                                Pre-Condition Time
                                                                                     0.5 day
                    0.004                                                             1 day
                                                                                      2 day
    Concentration




                                                                                      3 day
                    0.003
                                                                                      5 day
                                                                                      7 day
                    0.002


                    0.001


                    0.000
                            0.0   0.2      0.4     0.6    0.8       1.0   1.2

                                        Distance from the Die Pad



             Computer Aided Reliability Evaluation Lab.                                              54 / 74
        Temperature during the IR reflow process


   Temperature during IR process
       Temperature is spatially uniform during the IR process

                                   250


                                   200
               Temperature ( oC)




                                   150


                                   100


                                   50


                                         50   100    150     200   250   300

                                                    Time (sec)


     Computer Aided Reliability Evaluation Lab.                                55 / 74
                                   Concentration distribution
                                      at reflow soldering

        Model                                            Governing equation,B.C. and I.C.

                                                               C   C 
                                                                   D ,
                                                               t x  x 
                                                               C  C o ( x),   at t  0
          h                                                    C  P  S,     at x  0
                         x                                     C    Ps  S at x  h

                          a                               Accumulated mass at the die pad
Area of analysis
                                                                       t   C
                                                                m  A D      d
                                                                      0    x



              Computer Aided Reliability Evaluation Lab.                                      56 / 74
                                       Concentration distribution
                                          at reflow soldering

   Typical concentration distribution



                               0.004
               Concentration




                                                       150 sec
                               0.002                   170 sec
                                                       190 sec
                                                       210 sec
                                                       220 sec
                                                       230 sec
                               0.000

                                       0.0       0.1             0.2     0.3

                                             Distance from the Die Pad




     Computer Aided Reliability Evaluation Lab.                                57 / 74
             Relation between pressure and mass

   Equation of ideal gas                            Relation between pressure & mass


                                                            V
           pv  RT                                      v    ,
                                                           m
                                                        V  C1   max  A
    p : pressure (N/m2)
    v : specific volume (m3/kg)                               pa 4
                                                          C2 3
    R : gas constant (kJ/kg K)                                Eh
    T : temperature (K)

                                                                 m
                                  die pad                p  C3     ET
                                                                  A
                                   EMC



     Computer Aided Reliability Evaluation Lab.                                   58 / 74
                                             Vapor pressure
                                       during the IR reflow process

   Vapor pressure generated during IR process


                                0.60
                                         Pre-condition time

                                0.45           0.5 day
               Pressure (MPa)




                                                1 day
                                                2 day
                                0.30            3 day
                                                5 day
                                                7 day
                                0.15



                                0.00
                                          50         100       150     200   250   300

                                                              Time (sec)



     Computer Aided Reliability Evaluation Lab.                                          59 / 74
              Calculation of stress intensity factor

   Model                                            Method
       Stress analysis(FEM)                             Conservation integral : M-integral
       Calculation of SIF


                                                               M   Wx i n i  t i u i , j x j ds
                                                                       




                                                          W : strain energy density
                                                          ni : unit normal vector
                     p                                    ti : traction vector
                                                          ui : displacement




     Computer Aided Reliability Evaluation Lab.                                                   60 / 74
         계면박리와 균열에 대한 유한요소 해석

             Chip
             D/A                                       Thermal stress()
             Leadframe

             EMC
                       Crack                 Vapor pressure()


     D/A      Chip         Crack tip in EMC              EMC




     Delam.
                                        Leadframe
 C
 L

Computer Aided Reliability Evaluation Lab.                                 61 / 74
                                                   패키지의 건전성 평가


           Calculation of J-integral at package crack tip
           Comparison of J-integral(crack driving force) to EMC
            fracture toughness(resistance to crack propagation)

                        0.20

                                                                                            TSOP A
    J-Integral (N/mm)




                        0.15                                                                TSOP B
                                                                                            TSOP C
                                                                                            TQFP A
                        0.10                                                                TQFP B
                                                                                            TQFP C
                                                                             Crack region   SO A
                                                                                            SO B
                        0.05
                                                                                            SO C
                                                                                            Toughness

                        0.00
                                                                             Safe region
                               0   1     2     3     4     5         6   7
                                       Pre-condition time (day)


                        Computer Aided Reliability Evaluation Lab.                                      62 / 74
    패키지 균열의 거동에 관한 연구

        (Parametric study
on the behavior of package cracks)



Computer Aided Reliability Evaluation Lab.   63 / 74
                                    패키지 균열의 유형

   패키지 균열의 세가지 유형                                Two possible paths of the Type I crack




                                                    Simple path          Complex path
                                                  Two possible paths of the Type II crack




                                                    Simple path          Complex path

      Computer Aided Reliability Evaluation Lab.                                        64 / 74
                                 패키지 균열의 해석 방법

   패키지 형상                                               유한요소 해석




       Chip thickness = 0.3 mm
        L/F thickness = 0.15 mm
                                                         에너지 방출율 계산
    

       H = 1.4, l1 = 3.95, l2 = 4.25,                       M integral 사용
        L1 = 5.1, L2 = 6.75, L3 = 7.0,
        b = 0.3 (Unit : mm)                                   M   Wx i n i  t i u i , jx j ds


         Computer Aided Reliability Evaluation Lab.                                                   65 / 74
               Gmax vs. kink angle (Type II crack)

   Simple path Type II crack                       Complex path Type II crack




    Computer Aided Reliability Evaluation Lab.                                66 / 74
                                  Gmax vs. chip width

   Thermal loading                                  Pressure loading




     Computer Aided Reliability Evaluation Lab.                          67 / 74
                    Gmax vs. epoxy resin thickness

   Thermal loading                                  Pressure loading




     Computer Aided Reliability Evaluation Lab.                          68 / 74
                       Gmax vs. CTE of epoxy resin
                          and Gmax vs. pressure

   Gmax vs. CTE of epoxy resin                      Gmax vs. vapor pressure




     Computer Aided Reliability Evaluation Lab.                                 69 / 74
  MCM-D substrate의 열변형 해석


 (Thermo-mechanical analysis of
                   MCM-D substrate)



Computer Aided Reliability Evaluation Lab.   70 / 74
                                                  연구 배경

   MCM-D substrate : multi-layer                              failures : excessive
    polymer/metal structure                                     deformation/stress
                                                                    misregistration problem
                                                                       photolithography
                                                                       fine pitch wire bonding

                                                                    difficulties in basic process
                                                                       sawing
                                        Dielectric Film                vacuum mounting
                                        Adhesive Layer
                                                                    failure of films
                                        Metal Conductor
                                                                       adhesion reduction

                                        Silicon Substrate              variations in electrical
                                                                         properties
    Cross section of lamination based
    Si monolithic MCM-D substrate

         Computer Aided Reliability Evaluation Lab.                                                71 / 74
                  Lamination-based MCM-D substrate

          Specimen preparation                                             Measurement of bowing
                lamination process                                                  laser profilometry
                       150oC/50psi/40min                                            thermal cycling (25oC - 150oC)
                                                                                     scanning length Ls
                                Pressure                   Bladder
                                                                Rotating Mirror       Position Sensitive Photodetector

                                                                     Laser
                                Heater
Ring-Framed-Kapton
          Substrate
                                               Vacuum



          material properties and thickness(25oC)
   Materials          E (GPa)               a (10-6/oC)    t (m)                                  Lens
     Silicon            141          0.22        2.6         525
    Coverlay            0.5          0.37        60          50.8                     Substrate                             Substrate

                                                                                  Flat Substrate                         Curved Substrate

                 Computer Aided Reliability Evaluation Lab.                                                                     72 / 74
       Thermo-mechanical analysis
     (CBA, Composite Beam Analysis)


       R
                         T                                     T           M                       M
                   =                                                 + P
                                                                                                        P


   1   M                                               ˆ        ˆ
                          1 3           t
                       I  t s  t s (  s ) 2 
                                                   1   Ef 3
                                                         t 
                                                                Ef           tf         1 3
                                                                   t f (t s    ) 2  t s
       ˆ
   R Es I                 12              2       12   ˆ f
                                                       E        ˆ
                                                                Es           2         12
                                                        s


            ˆ
        1 6 E f t f DaDT                ts  t f           
                                                          
        R       ˆ 2
               Es t s                t E t /E
                                           ˆ      ˆ         
                                      s     f f    s       
                               ˆ         ˆ          ˆ ˆ
                             ( E s t s  E f t f ) E f E s t s (t s  t f )
            fm     ˆ
                   E f DaDT                      
                             (E          ˆ              ˆ
                               ˆ t  E t ) R(2 E t  E t )          ˆ
                                       s s       f f                s s      f f



Computer Aided Reliability Evaluation Lab.                                                        73 / 74
                           Experimental data and predicted data

                  Bowing due to thermal residual stress
                                                                                               Ls
                 2.0

                                  CBA
                                  ABAQUS
                 1.5
                                  Stoney's Formula                                                           B
dB/dT ( m/ C)




                                                                                               2
                                  Measured                                                   Ls
                                                                                        B
o




                                                                                             8R     (Ls = 10 cm)
                 1.0



                                                                                      2 ˆ
                 0.5                                                            dB 3Ls E f t f Da 
                                                                                                     ts  t f        
                                                                                                                      
                                                                                   
                                                                                dT      ˆ 2
                                                                                      4Es t s     t E t /E
                                                                                                        ˆ      ˆ      
                                                                                                   s     f f    s    
                 0.0
                    0.0         0.1          0.2              0.3   0.4   0.5

                                                   tf / t s




                          Computer Aided Reliability Evaluation Lab.                                        74 / 74

								
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