Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Silver Emerge

adam

#6881

Silver Emerge | 14 June, 2001

I'd like to know what advantages are there to use silver emerge PCB's. Currently we are using HASL boards, and we are having problems especially using BGA connectors. Any help will be appreciated. Adam.

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adam

#6883

Silver Emerge | 14 June, 2001

Sorry, wrong technical word I meant immersion silver (Ag). Thanks.

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#6899

Silver Emerge | 14 June, 2001

There�s tons of stuff on-line. Do a net search on "immersion silver". Examples are: * http://www.smta.org/knowledge/proceedings_abstract.cfm?PROCEEDING_ID=571 * http://www.enthone-omi.com/articles/FinalFinishesT1.pdf * http://www.epa.gov/opptintr/dfe/pwb/ctsasurf/download/pdf/app-b.pdf * http://www.enthone-omi.com/pdf/stafstromunraveling.pdf * http://www.circuitresearch.com/etin34_report.htm

Two comments:

1 Generally, immersion silver is an uncommon selection for solderability protection by those disenchanted with HASL.

2 On the surface of things, it seems a bit of a stretch to change from HASL to immersion silver [or any other solderability protection for that matter] on a board to solve "problems, especially using BGA connectors." So, before we let you go ahead and do that, let�s talk about those problems and see if we can reach some consensus here. Hey, wuddya loose?

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adam

#6912

Silver Emerge | 15 June, 2001

Thanks Dave.

About your second comment, the issue is placing BGA connectors mirror image (male, and female), the connector sometimes shifts during placement before reflow. we are using a six mil stencil for both sides with minimum paste deposit. also, I had to tape the connectors on the secondary side so that they woould not fall in the oven. This was done after trying numerous profiles. So I thought by using a board with a flat surface would help eliminate the placement problem.

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#6965

Silver Emerge | 18 June, 2001

Two things: 1 A flat surface will probably help the "balls on the socket sliding off the ridge of HASL" problem, but possibly consider less risky choices for your flat surfaces that immersion silver, like: OSP, ENIG, and immersion tin. 2 Don�t throw-away your tape use to "solve" your "sockets on the floor during second side reflow" problem, unless you do something different, like: * Reflow the sockets on the top side during the second side reflow. * Use a pallet. * Glue the socket after soldering them in-place. * Etc.

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