Hi all, I feel the need to restore the balance here before everyone starts
calling for other finishes unnecessarily; there can be solderability issues
with some of these.

If HASL induces bow then there is something wrong with the process method
unless the laminate is sub-standard. Flatness is not compromised if HASL is
done properly, particularly the post treatment. Usually bow is induced if
the panel is not kept flat and cooled below Tg before it hits the water
rinse. It is a harsh process which is why it is so good at weeding out
substandard laminate, plating, solder mask, or multi-layer bonding.

The PCB is subjected to other heat treatments during manufacture, such as
soldermask and ident bakes, and will also be subjected to uneven soldering
temperatures perhaps twice during assembly. If there is some problem with
the laminate then it is surely better to find out during circuit manufacture
than during assembly.

If the circuit manufacturer has a particular concern about achieving the
required flatness tolerance then they should raise it with their customer,
not extrapolate their problems to the rest of the industry.


-----Original Message-----
From: Jacob Mozel <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 22 July 1998 21:52
Subject: Re: [TN] Super flat PCB


>Hi Edward,
>
>I do believe that even by simply preventing the very harsh treatment of
HASL of the finished board one may
>improve the bow.
>
>Jacob

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