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January 2000

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Goh Guan Chye <[log in to unmask]>
Date:
Mon, 31 Jan 2000 07:19:59 -0600
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"TechNet E-Mail Forum." <[log in to unmask]>, Franklin <[log in to unmask]>
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Franklin <[log in to unmask]>
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Goh,

First, read IPC thoroughly again, measling is actually not cause for
rejection according to IPC-A-600/IPC 6012; however, it is indicitive of a
process problem.

If you are indeed seeing measling it could be due to entrapped moisture in
the board, you might try baking the board further prior to soldering.

Yes, the bare board should withstand temperatures required even to hand
solder,p rovided your soldering personnel are following the right methods,
if they use a pre-heater, have it set too high, or level the soldering iron
in contact with the board too long you may find that to be the cause, but I
believe you would see other laminate or solder mask damage first? Do you see
those conditions?

My recommendation is to bake the boards in accordance with your board
suppliers guidelines prior to performing ANY soldering.

Good luck

Franklin D Asbell
Network Circuits, Inc.
Irving, Texas
972-313-1400



----- Original Message -----
From: Goh Guan Chye <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, January 31, 2000 3:27 AM
Subject: [TN] Measling after soldering


> Hi ! Technetters,
>
> May anyone advise a measling problem after manual soldering.
>
> We have a batch of PCBA spotted with measling after manual soldering.
> These measling happen surround the areas with large copper plane. This
> is a 14-layer design (2.9mm thick) with 6 layers of large copper areas
> (not full plane). Due to heat sinking problem, we use solder temperature
> of 350 degC and the soldering duration is about 2-3 secs. To analyse on
> the problem, we wave the assembly at solder bath temp of 250 degC, no
> measling found.
>
> The question now is, this is not the first time that we manual solder
> high layer count MLB with large copper plane. We did not find any
> measling problem. In such case, what could it be due to ? The bare board
> quality problem ? Should the bare board must be able to withstand the
> manual soldering that we used ?
>
> If the measling doesn't meet the IPC acceptance criteria, would it
> affect the bare board's reliability ?
>
> Thanks for your attention and have a nice day.
>
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