HASL plating thickness spec

[jim bubenko]

Hi Guys, we have over the years developed a section of notes on our fab drawings. I have a note on this drawing that a reputable board house took exception to and was wondering if perhaps this note was outdated due to process improvements. It has been in our standard notes for 11 years. The part that was discussed was the .0003 inch crest. My QA guy believes that much less than this will allow for copper migration and affect solderability thus lowering the shelf life of the boards.

Any assistance will be appreciated.

Here is the note.

All Monmasked area except gold plated contacts shall be protected with a solder coating of .0003 inch minimum at crest and .0001 inch minimum in plated thru holes. Tin-lead plated areas to contain 60% +/- 10% tin. Exposed copper will not be permitted. Solder used must meet QQ-S-571.

[Tom]

Jim,

HASL has the largest tolerance factors in the manufacturing industry. The key problem with HASL processes is that solder thickness varies widely from 0.75um (.00003") to 35um (.0014"). Manufacturers cannot hold a HASL tolerance of 7.5um (.0003"). HASL is too unstable and difficult to control. You need to switch to a Gold or Silver finish and dump HASL.