Frank,
Your board supplier needs to be more specific when stating 40-1000
microinches. The problem is (with most HASL machines) getting consistent
thickness across surface mount pad sizes which vary in length and width. For
instance, if you have a SM pad that is .300 x .100 vs a pad that is .40 x
.075, the smaller pad will attract a greater thickness of solder. Generally
the larger the
land area the more difficult it is to achieve sufficient solder thickness.
Horizontal
solder machines probably can give you the best solder coverage, but not too
many board suppliers can afford a 150K solder machine.

Tony Steinke
Circuit Technologies Inc.
[log in to unmask]
----- Original Message -----
From: Frank Kimmey <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, August 22, 2001 10:13 AM
Subject: [TN] HASL Thickness


> Good Day to all,
>
> Hope you can assist with a HASL question (Werner are you out there?)
>
> We are considering some new vendors and they are requesting we reduce our
> HASL thickness requirements.
> We presently spec 100 to 500 microinches and vendors say they would like
to
> see 40 to 1000 microinches.
> Now the questions:
>
> 1. Will 40 microinches cause intermetallic issues?
> 2. Will 40 microinches cause major shelf live issues?
>      Expected shelf life 3mos, 6mos, 1 year for sealed in plastic, low
> humidity?
> 3. Since I am not comfortable with 1 mil of tin/lead should 500
microinches
> be enough?
>
>
> I appreciate you comments (Steve, Dave, everyone).
> Thanks in Advance,
> FNK
>
>
> Frank N Kimmey, C.I.D.
> Senior PCB Designer
> Powerwave Technologies
> PH. 916-941-3159
> Fax 916-941-3195
>
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