Hi Jim...well...yes it can be controlled in a "range". The HASL process is "geometry dependent" meaning that it is repeatable and controllable on like pad sizes and shapes. Typically, the operator will select the smallest land or pad area as a target site (these small sites tend to resist the leveling efforts of the air knives most, and are the first place to lose control (too thick, improper hole clearing, etc). Once control has been established in the critical areas ( adjustment in thickness is possible) in a range generally within a couple hundred micro inches). This air pressure setting and knife angle will now be leveling all sites. In surface mount and some mixed technology designs, the larger land areas can get pretty skinny. ( maybe a little less than 100 micro inches) this has long been a point of controversy with regards to shelf life and solderability. History has shown us however, that while the deposits can be very thin, (in some areas) shelf life of a least a year under normal storage conditions is common.
I hope this isn't more than you wanted to know. I have been involved in this process from its inception and tend to over simplify sometimes.
hoping this helps,
Mark Simmons, V-Score Central, Inc.

West, Jim wrote:

[log in to unmask]">

Hi,

Can the Height of HASL be controlled?  I have seen the process but don't
remember exactly where there are any control points.

Thanks,
Jim West

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