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					                                                       Lead Free Solutions for Assembly and Packaging




        Analysis of Lead-free Hand
        Soldering Processes

                   Erik Veninga
                   TNO Science and Industry




1   5 April 2006   SEMICON Europa 2006   - Munich, Germany
                                                              Lead Free Solutions for assembly and Packaging"




         Outline
    •     Craft project: LFS for SME’s
    •     Manual vs. Reflow
    •     Soldering times
    •     Through-hole filling / ultrasonic soldering
    •     SnZn solder wire




2   6 April 2006      SEMICON Europa 2006 - Munich, Germany
                                                                       Lead Free Solutions for assembly and Packaging"




           Craft project: LFS for SME’s
    Work package Manual Soldering:
    1)       Study joint quality and thermal impact on components
    2)       Reduce and control process variations
    3)       Development lead-free solder wire

    Partners WP Manual Soldering:
    •         12Assemble (Cable assembly) – Peter van Zanten
    •         CHK (Printed circuit board assembly) – Steve Scarlet
    •         Betronic (Hybrids and printed circuit board assembly) – Wim Geerlings / Wim Schmitz
    •         Radiel (Dev. and manuf. solder wire) – Nicolas Winkler / Francois Millet
    •         Irepa (Manual laser soldering) – Didier Boisselier / Cédric Chaminade




3       6 April 2006           SEMICON Europa 2006 - Munich, Germany
                                                                                          Lead Free Solutions for assembly and Packaging"




         Lead-free hand soldering
    Literature study
    - Searched in 18 databases
    - Key-words (in title and text): lead-free AND solder* AND manual OR hand
    - Only 11 relevant titles found at start of the project
    - Most useful articles were found in assembly magazines
    - Beside t=0 quality, no reliability data found

    Analysis of the process
                    Examples QMAP / Maturity Matrix results
                    QMAP                                                                            Risk
                               Potential risks
                    process                                                                      assessment
                    A-2        New workmanship / working methods needed?                             A3
                    A-2        Current (wave soldering) design rules adequate enough?                A3
                    A-2        Tip life significantly shorter?                                       C3
                    A-2        Lead-free manual soldering more expensive?                            B2
                    A-2        Significant higher variation on tip / peak temperatures?              S3
                    A-2        Significant higher variation on soldering times?                      S3


         Overall conclusion analysis potential risks (39 in total): most causes are known and
         understood. Important now: 1) investigating the impact of potential risks, 2) development of
         solutions and 3) testing adequacy of available solutions.

4    6 April 2006                        SEMICON Europa 2006 - Munich, Germany
                                                                     Lead Free Solutions for assembly and Packaging"




           Manual vs. Reflow (1)
    Benchmark manual process with process
    having high reproducibility regarding soldering
    temperatures and solder volumes.
    Materials
    Components: 0805-R / C (tin plated), 1206-R / C (tin plated)
    Board: FR4 test board (design by Betronic), Ni-Au finish
    Solders: Wire: SnAg3Cu0.5, d=0,7mm, 1.4% Rosin flux,
    paste: SnAg3Cu0.5, RMA

    Equipment
    Soldering iron: Advanced JBC - AD 2200 (55 Watt),
    temperature setting 350 °C, small tip (type 32)
    Stencil: stainless steel, 125 um thickness, laser cut
    Forced air conv. reflow oven: Techno print - Techno HA-02

    25 Manual test boards (1000 solder joints in total)
    25 Reflow test boards ( ,,      ,,     ,,    ,, )



5      6 April 2006          SEMICON Europa 2006 - Munich, Germany
                                                                                                                       Lead Free Solutions for assembly and Packaging"




                        Manual vs. Reflow (2)
    Results manual soldering: visual inspection according to IPC-610 rev. D:
                                 IPC Class          Defects per Million       Defects per                      Yield
                                                      Opportunities              Unit           (Y = e
                                                                                                                     − DPU
                                                                                                                             )
                                                        (DPMO)                  (DPU)
                                     I                  2000 ppm                 0,08                   92.3 %
                                     II                   ,, ,,                    ,,                      ,,
                                    III                 9000 ppm                 0,36                   69.8 %


                               60   56                                                          100
                                                                                                90                    Pareto analysis
                               50                                                               80
    Number of Defects




                                          39




                                                                                                      Cumulative %
                                                                                                70
                               40
                                                                                                60

                               30              28                                               50
                                                                                                40
                               20                                                               30
                                                     9                                          20
                               10                         7
                                                              2                                 10
                                                                   1      1   1    1   1    1
                                0                                                               0

                                                                                                               Comments soldering technician:
                                                                 C




                                                                 R

                                                                eb
                                           tH t0 R
                               um t H t 0 R



                                                    ht 5-C




                                                         08 t
                                                                 C




                                         iv der 6-R



                                                    lle 5-R
                                        im lder 6-C
                                                                th




                                                               gh

                                                   So 05-
                                                              5-
                                                              5-
                                                   gh 06-




                                                   Jo 06-

                                                             id




                                                             w
                                                            ei
                                              so 080
                                                          80

                                                          80




                                              s o 1 20

                                              so 120

                                                            0
                                   es w h t W




                                                                                                               - “Smaller wetted area”
                                                          er
                                                          2




                                                        12




                                                        08

                                                        tH
                                                      t1




                                                       ld
                                                      in




                                                     le
                                                      e

                             Ex ive er
                                        lle igh



                                        lle igh




                                                   ol




                                                 ho
                                      um eig




                                                 Fi
                                                 ld
                                                ei




                                                                                                               - “Significant more time needed”
                                                 l
                                                e



                                                e



                                               d




                                            um

                                            ow
                               um et H

                        M um t H




                                           En

                                            o




                                           e
                                           e
                                         Bl




                                         Bl
                                        lle




                            Ex siv
                                        ll




                                       s

                                    ss




                                                                                                               - “Tendency to reject / rework joints”
                                    Fi

                                    Fi

                                    Fi

                                    Fi




                                     in
                                   es
                                  im




                                   M
                                 ce
                        M um




                                ss

                                ss
                               in



                            Ex
                            im

                            im
                            im




                            im

                             M
                         ax

                          ax
                         ax




                         ax
                        M
                        M




6   6 April 2006                               SEMICON Europa 2006 - Munich, Germany
                                                                                               Lead Free Solutions for assembly and Packaging"




         Manual vs. Reflow (3)
                                               Temperature cycling profile
                        140

                        120
                                                    20 min
                                  3,33 C/min
                        100
      Temperature [C]




                        80
                                                                              2,27 C/min
                        60

                        40

                        20
                                                                                                 20 min
                         0
                              1     9   17 25 33      41 49 57 65 73 81 89           97 105 113 121 129 137 145
                        -20

                        -40

                                                                   Time [min]
                                          Visual inspection / Shear testing / Cross sectioning
                                          @ n=0, 250, 500, 750, 1000, …...... cycles

7   6 April 2006                                 SEMICON Europa 2006 - Munich, Germany
                                                                                                                                               Lead Free Solutions for assembly and Packaging"




                               Manual vs. Manual (4)
                                          0805-R                     Temperature cycling [-25/+125C]
                           10,0
                            9,0
    Shear strength [kgf]




                            8,0
                            7,0
                            6,0                                                                                                      Max.
                            5,0                                                                                                      Min.
                                                                                                                                     Average
                            4,0
                            3,0
                            2,0
                                          Manual                                           Reflow
                            1,0
                            0,0
                                                                            n=……..




                                                                                                                            n=……..
                                    t=0




                                                                                     t=0
                                          n=250

                                                  n=500

                                                          n=750




                                                                                           n=250

                                                                                                   n=500

                                                                                                           n=750
                                                                  n=1000




                                                                                                                   n=1000




                           Component metallization torn away
                                                                                                                                                 Manual 0805-R (n=750)



8                          6 April 2006                                    SEMICON Europa 2006 - Munich, Germany
                                                                                                                                               Lead Free Solutions for assembly and Packaging"




                               Manual vs. Reflow (5)
                                            0805-C Temperature cycling [-25/+125C]




                                                                                                                                                                                         ~ 80 um
                           10,0
                             9,0
    Shear Strength [kgf]




                             8,0
                             7,0
                             6,0
                                                                                                                                     Max.
                             5,0
                                                                                                                                     Min.
                             4,0                                                                                                     Average
                             3,0
                                                                                                                                                    Reflow (n=750)
                             2,0
                                           Manual                                          Reflow
                             1,0
                             0,0
                                                                            n=……..




                                                                                                                            n=……..
                                           n=250

                                                   n=500

                                                           n=750




                                                                                           n=250

                                                                                                   n=500

                                                                                                           n=750
                                     t=0




                                                                                     t=0
                                                                   n=1000




                                                                                                                   n=1000




                                                                                                                                                                                         ~ 5 um
                                          Difference in solder volume
                                             and solder height                                                                                        Manual (n=750)


9                          6 April 2006                                     SEMICON Europa 2006 - Munich, Germany
                                                                                                                     Lead Free Solutions for assembly and Packaging"




          Soldering times (1)
     Reference process                                            SnPb37 (Rosin flux), Imm. Ag boards

                                             TC




                                             Histogram (n=35)                                             Normal-scores plot
                            12                                                                                 5,0
                                                                                                               4,5                  2
                            10                                                                                                     R = 0,9946
             Frequency of




                                                                                                               4,0
              Occurence




                             8
                                                                                                               3,5
                                                                                                               3,0
                             6                                                                                 2,5
                                                                                                               2,0
                             4
                                                                                                               1,5
                                                                                                               1,0
                             2
                                                                                                               0,5
                             0                                                                                 0,0
                                 2,2   2,6      3,0   3,4   3,8   4,2   4,6   5,0   -1,500   -1,000   -0,500     0,000     0,500        1,000   1,500   2,000

                                                Soldering time [s]                                                   Z-Score


                                                Assumption: process is normally distributed

10   6 April 2006                                     SEMICON Europa 2006 - Munich, Germany
                                                                                       Lead Free Solutions for assembly and Packaging"




            Soldering times (2)
     Cycle time comparison:
     Reference process: avg = 3.4 s, stdev = 0.5s
     Experiments
     Wires: SnAg3.8Cu0.7 (1 mm diam.), Flux type: rosin
     PCB: FR4 (1.6 mm), Imm. Ag. Components: DIL-16, Sn plated
     Solder station: 50 Watt iron

     Statistical analysis: SnAg3.8Cu0.7 settings vs. SnPb37
                                                                       Exp.      1           2           3           4
                                                                    Avg [s]     2.4         3.9         4.6         3.6
                                                                 Stdev. [s]     0.8         1.9         1.3         1.3
                                                                  S-N ratio    -7,85      -12,69      -13,61      -11,58
                                                            T-test, one tail
      Significant difference on soldering time?                                 N            Y           N           Y
                                                               (α=0.05)
                                                                 F-test
      Significant difference on variation soldering time?                       N            Y           Y           Y
                                                               (α=0.05)




11     6 April 2006                SEMICON Europa 2006 - Munich, Germany
                                                                                                       Lead Free Solutions for assembly and Packaging"




         Soldering times (3)
                                                           Main effects and interaction
                                          5
                                         4,5
                                                                                               1,4 % Flux
                                          4
                    Soldering time [s]




                                         3,5
                                          3
                                                                                               0,9 % Flux
                                         2,5
                                          2
                                         1,5
                                          1
                                         0,5
                                          0

                                               0,9 % 1,4 %               T set = T set =              T set = T set =
                                               Ri Flux Ri Flux            375C 425C                    375C 425C
                                                 (5)     (4)

            Flux content has a significant influence on soldering time, best results
            in combination with higher temperature setting (also highest S/N ratio)


12   6 April 2006                                      SEMICON Europa 2006 - Munich, Germany
                                                                                                                                                                  Lead Free Solutions for assembly and Packaging"




                 Through-hole filling (1)
     Pareto analysis RoHS compliant test product CHK
                             90                                                                                                                             120
                                        80
                             80
                                                                                                                                                            100
                             70                            62
         Number of Defects




                             60                                                                                                                             80




                                                                                                                                                                  Cumulative [%]
                             50
                                                                                                                                                            60
                             40

                             30                                                                                                                             40

                             20                                              18
                                                                                                                                                            20
                             10
                                                                                               1               1                1                1
                              0                                                                                                                             0
                                     Blow holes    Solder fill is less   Convex fillet      Wetting on Fillet and wettingSolder splashes / Solder has not
                                  (conn. meets all    than 75%                           primary side of on second. side     webbing       wetted lead or
                                     other min.                                          lead and barrel   of lead and                          land
                                     requirem.)                                           less than 180 barrel less than
                                                                                                                270



                                                 Most important critical failure mode in this analysis
                                                 (blow holes were process indicators)

13   6 April 2006                                                        SEMICON Europa 2006 - Munich, Germany
                                                                             Lead Free Solutions for assembly and Packaging"




          Through-hole filling (2)
     Hand soldering assisted by ultrasonic energy
     Equipment: S-Bond Mini, 60 kHz




                    Wetting at top side          Sunken fillet and flux    Potential failure mode:
                                                 degradation at            sudden transformation
                                                 bottom side               solder into powder.




14   6 April 2006                  SEMICON Europa 2006 - Munich, Germany
                                                                    Lead Free Solutions for assembly and Packaging"




          Through-hole filling (3)
                       SnAg3.8Cu0.7 / Ni-Au                   SnAg3.8Cu0.7 / Cu
      US Energy:




      Conventional:




15   6 April 2006     SEMICON Europa 2006 - Munich, Germany
                                                                       Lead Free Solutions for assembly and Packaging"




         Sn-Zn Solder Wire (1)
     Advantages Sn-Zn                             Concerns Sn-Zn
     Relative low melting point                   Corrosive behaviour Zn
     (Tm SnZn9 = 199 °C)                          Not compatible with all metallization / base materials
     Low cost                                     Large variation on joint quality
     No “environmental issues”                    Uncertainties about reliability




     Alloy supplier: Mat-tech                     Wire manufacturing: Radiel
     Composition: SnZn9                           Versions: 2.2 wt.% RA flux / no flux
     Purity: Sn = 99.85 %, Zn = 99.7 %            Diameters: 1 and 1.5 mm
     Cylinders: d = 72mm, l = 180mm

16     6 April 2006         SEMICON Europa 2006 - Munich, Germany
                                                                   Lead Free Solutions for assembly and Packaging"




         Sn-Zn Solder Wire (2)
        SnZn9 joints on Ni-Au (2.2 wt.% rosin activated flux)




     Temp. Setting iron:
     350 - 375 °C




17   6 April 2006          SEMICON Europa 2006 - Munich, Germany
                                                                                                                                      Lead Free Solutions for assembly and Packaging"




         Sn-Zn Solder Wire (3)
     Pareto                             160

                                                    137
                                                                                                                                                         120

                                        140
     Analysis       Number of Defects
                                        120
                                                                                                                                                         100




                                                                                                                                                               Cumulative [%]
                                                                                                                                                         80
                                        100

                                         80                                                                                                              60

                                         60
                                                                                                                                                         40
                                                                    37
                                         40
                                                                                   23                21                                                  20
                                         20
                                                                                                                         4                 4
                                          0                                                                                                              0
                                              No fillet primairy   Icicles   Solder splashes /   Convex fillet   Fillet and wetting Fillet and wetting
                                                   side (incl.                   webbing                          on second. side on second. side
                                              insufficient hole                                                  of lead and barrelof lead and barrel
                                                filling errors)                                                    less than 270      less than 330




18   6 April 2006                               SEMICON Europa 2006 - Munich, Germany
                                                                         Lead Free Solutions for assembly and Packaging"




         Sn-Zn Solder Wire (4)

                                                                         Top fillet missing




                                                                         Vertical fill of solder <50%

                                                                         Vertical fill of solder ~ 75%

           X-ray                                                         Poor fillet bottom side


           X-ray image SnZn9 soldered DIL-16 IC’s



          Important concern: variation on results


19   6 April 2006                SEMICON Europa 2006 - Munich, Germany
                                                             Lead Free Solutions for assembly and Packaging"




         Next
      • TCT through-hole joints SnZn9
      • TCT hybrid circuits (Al2O3 / Ag-Pt thick film)
        passive components soldered at different
        temperatures
      • Analysis design rules / guidelines
      • Development manual laser soldering tool




20   6 April 2006    SEMICON Europa 2006 - Munich, Germany
                                                            Lead Free Solutions for assembly and Packaging"




         Thank you for your attention

          Questions?




21   6 April 2006   SEMICON Europa 2006 - Munich, Germany

				
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