Laser cutting and scribing of ceramics by rey15315

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									       TECHAPPLICATION



       Published by the EPRl Center for Materials Fabrication                                               Vol. I, No. 5 , 1987


       The Challenge: Keeping Ahead of Customers'
       Tightening Specifications



       T
              he electronics industry IS rapidly developing new
              uses for ceramic         and
                              materials demanding    shapes
              that meet Increasingly stringent specifications. A
       company that scrlbes and machlnes ceramlcsfor the elec
                                                                      I
       tronlcs Industry hears a clear message from its customers
       either meet the new specifications or get out of the
       business.
          But Diversifled Manufacturing, Incorporate(
       (DMI) of Lockport, New York, has no intention
       of getting out of a growing market. In 1986
       when Its current laser equipment could not
       make the higher quallty cuts that customers
       were demandlng, DM1 opted to invest in a
                                                                                     of ceramic substrate because it produces
       new laser system which could give:
                                                                                     no mechanical stress. After the parts (left)
       B Faster scrlblng and deeper penetration                                      are scribed andlor cut byDMI, the custom-
'''~      Higher-quality machining with cleanedges                                   er can solder wiresto the electronic
          Better pulse control                                                       component and trim the part by snapping
                                                                                     along the scribe lines.
          Improved equipment reliability and less
          downtime
                                                                        The basic difference between SAF and FAF lasers is the
       The Old Way                                                    amount of power that each can output. The FAF lasers can
                                                                      achleve higher output powers dueto the way that each dis-
          A customer would describe the needed designto DM1           poses of the excess heat that is a natural byproduct of
       by a blueprint, a sketch or a phone call. DM1 produced a       lasing.
       CNC (computer numerical control) tape for its laser cutting      After consulting laser manufacturers, DM1 purchased a
       system and then made the part. Lot slzes ranged from 1 or      600 watt FAF CO, laser mainly because of its improved
       2 prototype parts to productlon runs of thousands of parts     pulsed beam. In addition, a FAF laser was about 30% less
          The ceramic alumina sheet would be held in place on a       expensive than a SAF laser which would have given the
       computer-controlled XY table with a vacuum chuck. For          same cutting rate. Fortunately, DM1 did not need to buy any
       scribing, the laser was pulsed on and off to produce a row     new computer or support equipment. Thus,within 2
       of holes. A pulsed beam was also used for cutting.             months of purchase, the new laser was in operation.
           DM1 was using a 150 watt slow axial flow CO, laser (SAF)
       which had shortcomings including:
                                                                      Results: Increased Production and
          The equipment needed to be recalibrated frequently, and     Improved Quality
          tight speciflcatlons could not be met
                                                                         Fewer rejects. Scrap rate has been reduced from 10%
       rn A 2-hour daily start up.                                    to 0.5%.
          Uneven heating from the unstable beam sometimes                Higher quality cuts. The laser beam I S stable, so heat
          caused mlcrocracks on the machined edges.                      input to the workpiece is constant. Thus, microcracking
           Dlamond cutting was an alternative technology to meet-        is less of a problem.
        ing customers' demand for high quallty cuts However, dia-        Round, clean holes when scribing. Material is vaporized
        mond blades wear out, and the process is slower and more         thoroughly, so there is no redeposition. And precise
        expenslve than laser cutting.                                    on-off gating of the hlgh voltage discharge means sldes
                                                                         of holes are perpendicular.
       The New Way                                                       Even scribing. The pulse frequency of the new laser can
          Slnce a laser is the preferred tool for processing             be changed instantaneously ("on the fly") under com-
       ceramics, DM1 sought a replacement for its SAF CO, laser.         puter control so decreasing the pulse rate to match a
       Options were another SAF laser or one of the new, fast axial      decreased table speed as it changes direction is no
       flow lasers (FAF) developed within the last 4 years.              longer a concern.
    up to 100 thousandths an inch versus 50 thousandths
                          of
    with the old system.
      F a B t ~ 8 n d ~ B e c e u s e o f t h e m r w
    laser's i c
            n-        pcmer and reduced maintmence require-
    ments, DM1 can quickly produce to customers'
                                       its
    specifications.
      tp d m d o n God Faster processing and
    ducn#reed.downtime mean a lower cost per part.
      L" -                    laser is 10%
                      DMl's new                   than
                                            smaller the
    old one acd 10% of the size of a SAF laser of equivalent
    PRm.
                    .the old SAF only warm-up productiw for
                      With 1 hour for
                                      could be
                                               and 1 hour

                                  600 watt SAF laser takes 20
                                 inutes for beam alignment
                             85% of the day. With 12 minutes
                             could be productive  93% of

                      laser consumed6 kW while bdh newer
                      e 12 kW. Although the energy consumption
               Ihe new scribing rate doubled and the cutting
                than tripled. When combined with the over-
                .reduction in scrap rate and increased productiv-
    ity, the averall energy usage per part wasreduced
    tremendously.
       L                            . a
                          c a a o small
                         a p ? o Only            wlume of laser
    gases are required, and the small closed-loop system it
    u m minimizes gas consumption.
                #ktr.       Because of design i m p m m t s ,
    msintsnance technicians are not exposed to dangers
                                                    the                               ners, Gordon(left) and Jack, continually
    of high voltage while adjusting the cavity mirrors.                                                                 to
                                                                                         their manufacturing operations meet the
         m
       N u ~ U W With higher peak powers
                         R                       from
    k m , M can naw scribe and drill a greater
              I                                     vare
    s&aiee as w l as new composite materials.
                   el

          WRAaC08t?
      DIyIb rmw krer cost about $70,000.A complete laser        $!#
               8 y s t 8 m , including an XY tabk andacontrol     -A
    canput.r, wDu)cf cost around $200,000.DM1 expects           >,,    '
    a plybrdc psriod of about 2 years on its new laser.          J



                                                                ~,.*  '.
    tw
    'l "
       W l b pIoduct quality naw meets or exceeds that of
                                                        i
    o m d w ,so there is no problem in meeting custome
      o p& s



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