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December 1998

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From:
Gallagher Bob <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 1 Dec 1998 09:30:36 -0000
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Be very aware that when scoring loaded boards you increase the flexure on
the pcba's. Aside from running the risk of fracturing solder joints and
possibly creating intermittant and undetectable open ccts, you run the risk
of cracking components which may or may not show up on test and may also
contribute to early life failure. I would suggest either

1 - that you regulate and define your process exactly to ensure repeatable
scoring. Same for breakout.

2 - test the possible variances in scoring for damage. Consider a life
test/humidity tests (cracked components let in moisture). Assess your risks
for the consumers uses.

3 - scrap the boards and take no risks!


Regds

Bob Gallagher

-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: 01 December, 1998 12:04 AM
To: [log in to unmask]
Subject: Re: [TN] Scoring PCAs


In a message dated 11/30/98 3:34:45 PM Pacific Standard Time,
[log in to unmask] writes:

<< Address,

      I have a PCA that was once routed using a phenolic base (Jig).  The
      base and Router are no longer available.  The fix is to score the
      panels prior to assembling.

      The immediate need is, "How do I depanel existing PCAs?"  Again, the
      panels have NOT been scored and the router/base are not available. Is
      it possible to score the PCA with components loaded?  I could then use
      a depanelizer such as CAB.  Alternatively, could I use a skip Router
      for depaneling PCAs?

      This is a .028, std. 1 x 4 array, PCMCIA application.  Any advice as
      well as service bureaus to perform any of the above or any other
      suggestions.  Preferably someone local to Dallas, TX.

      John Gulley
  >>

Hi John!

     I know somebody that'll do it out here in California, did the same
thing
for me one time with loaded boards. We were building Toshiba laptop memory
and
the score job wasn't checked on the fabs when we recieved them. Got the
boards
built but couldn't singulate them without flexing the boards big time
because
of the insufficient score depth, and I was worried that we would fracture
solderjoints it was that bad.

     Called quite a few fab shops around here but couldn't find anybody at
first that wanted to do the job. Couple of problems, nobody had the kind of
scoring equipment that had enough clearance to score a loaded board.
Apparently the newer generation scoring machines need more clearances than
the
older machines did, and make it difficult (if it can be done at all) to
score
populated fabs.

     The other problem was that many shops aren't really ESD safe back in
their scoring and routing areas...they don't need to be either, copper and
fiberglass the last time I checked, wasn't ESD sensitive....   :^)

      The shop I found is "Onanon"....(408) 262-8990, ask for Dennis
Johnson.
The shop is out here in Milpitas, California. All they do is route, score,
and
drill. Dennis set-up one of his older machines for me, and grounded the area
around the scoring machine to do the job...couldn't ask for more.

-Steve Gregory-

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