Ioan,

Try 1000 microinches maximum (1 mil) ... and require them to measure the
finest pitch pad (20 mil pad width will usually have between 200-900 micro
inches (I'm familiar only with vertical HASL...the horizontal HASL is
supposed to be a lot more uniform) and still have sufficient coverage on the
larger pads.
If you specify that the larger pads are only covered, or have a minimum of
50 microinches, the fab guys should be able to make your boards without the
large (2 mil) bumps on the small pads.

Douglas Corbett

-----Original Message-----
From: Tempea, Ioan [mailto:[log in to unmask]]
Sent: Tuesday, March 09, 2004 12:31 PM
To: [log in to unmask]
Subject: [TN] Finish thickness for HASL
Importance: Low


Dear Techons,

I know that this issue has been discussed several times, but I would like to
check again for updates and new issues.

What is a good specification for the thickness of the HASL finish, that
would not make it impossible for the PCB fabs and it would avoid me
receiving boards with 2-3 mils thick bumps on the fine pitch?

Thanks,
Ioan

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