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Reply To: | TechNet E-Mail Forum. |
Date: | Sat, 24 Jan 1998 10:12:25 -0800 |
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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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