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January 1998

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Subject:
From:
Karen Tellefsen <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Sat, 24 Jan 1998 10:12:25 -0800
Content-Type:
text/plain
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text/plain (48 lines)
Mark Simmons wrote:
>
>
>
> Some of the advantages to HAL are:
> 1.  Solderability.  Nothing solders like solder.

Absolutely, probably HASL best advantage.

> 2.  It assures the solderability of the plated copper and previews
>     general thermal fitness prior to component attachment.
> 3.  Excellent shelf life.  Better than a year in normal conditions (like
>     your desk drawer)
> 4.  Less contaminants like Cu in the solder joint. (since Hal establishes
>     the inter-metalic, you attach to solder.)
> 5.  Plated thru holes sure solder nice. (have we gotten rid of those
>     pesky holes yet?)
> some of the dis-advantages are:
> 1.  Planarity.  Somewhere around 6 to 8 mil pitch, it gets a bit
>     difficult to control thickness. (the process is geometry dependant)
>
> With respect to BGA's, with modern HAL equipment, they are being
> processed routinely worldwide.
>
> With respect to Cleanliness, <3 mg. cl. sq. in. is routine on modern
> equipment.

You'd probably get < 3 mg Cl/in^2 even if you clean in ice cold tap
water for 5 seconds.  (m = milli)

However, 3 micrograms Cl/inch^2 on HASLed boards, while do-able with
modern PC fab equipment, is hardly routine except for the best
fabricators.  That is unless one measures ionic contamination with an
unheated Omegameter with a test time < 4 min as is done by many PC fab
shops.  A lot of HASLed boards are pretty dirty, ionically speaking.

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