My last HASL concerns all that has been said before. Some say we should move on, quit beating a
dead horse, and find alternative surface coatings. Some say the issue is too important to be
ignored. Obviously I, as do many others, agree with the latter while wanting an effective
alternative to HASL.

One of my biggest problems with HASL was brought to light by Sarif when originally he asked if
there could be negative affects caused by repeated attempts at solder wetting during the process. I
said there would be as indicated in my responses. Some others didn't even read Sarif's question but
jumped on latter responses.

One person said that HASL is very representative of subsequent soldering operations. This is not at
all so. The single reason for this, and for one of the biggest problems associated with HASL, is
that all other soldering operations rely heavily on solder termination areas with some type of
oxide preventive coating. In HASL, there is no such protection.

Before HASL, printed circuit panels are copper plated and most often, now days, micro-etched to
remove and/or minimize oxidation. The big "rub" comes when the panels are dried, as they must be
before any soldering operation, thus providing the mechanism promoting oxidation. Often the
oxidation is excessive and very active fluxes are required in an attempt to remove the
contamination. Often, this does not work and non-wetting is the effect. Also, as stated by many,
different flux types provide their unique set of problems.

The reason tin/lead plated/fused boards work so well is they stay "wet" throughout their process
lives. They don't have a chance to oxidize when processes are managed effectively.

Flux note: I agree that titration is an ideal way to determine flux quality, composition, and
effectiveness. How many contract manufacturers have the capability, time, or even knowledge of this
practice. Besides, when running a high number of boards per shift or day, it's easier to check
density and replace flux often instead of diluting. In most board shops, labs are available to do
chemical analysis.

Earl Moon

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