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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Solder wetting test for PCB's

Rich

#6052

Solder wetting test for PCB's | 23 April, 2001

I am looking for a repeatble method to determine the quality of solder wetting to a PCB. I would like something that I can perform in-house, at low cost, with reliable results. My goal is to test the wetting on white-tin PCB's, after repeated reflow cycles. All input is greatly appreciated.

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#6056

Solder wetting test for PCB's | 23 April, 2001

Step 1: Print paste on the board, skip placement, reflow the board, check solderability. Step 2: Goto Step 1.

White Tin Solderability: The most common reason for solderability issues with the white tin surface coating during multiple thermal excursions is a low white tin deposit. Florida Cirtech recommends 0.65 microns thickness, that has proven to be sufficient for at least one year shelf life and up to four passes in assembly. In almost every case we've seen, when the first pass or two solders fine and then problems arise, it is an insufficient thickness of white tin that was on the board.

Specify IWT: Immersion white tin with a minimum thickness of 0.65 microns with a maximum thickness of 1.5 microns.

You didn't say if your supplier was using either a Dexter or a Omikron [Florida Cirtech ] process. Dexter may have different recommendations for minimum thickness. With both processes, suplliers need to focus on proper process control and monitoring. Consider asking your quality assurance team to set-up a monitoring assessment program with your supplier.

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Rich

#6057

Solder wetting test for PCB's | 23 April, 2001

Thanks for the instructions. I was missing the reflow part...

Omikron is the method our board house offers.

We have been through the plating thickness problem and tin depletion conditions. Beyond those issues, I have been trying a few different no clean solder pastes (Aim 293+, Aim 250, Florida Cirtech) to try to improve wetting through slightly more agressive fluxes. (I know, I know "aggressive" no clean????)

Carefully read the method of testing in the published data from Omikron, regarding the test they perform for wetting. (photo-copies?!?!) This is why I am looking for a better method.

Everything we process is exposed to at least 2 reflow cycles and 1 pass over the wave solder.

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#6058

Solder wetting test for PCB's | 23 April, 2001

I agree that solderability is THE issue, but we choose not to get into that pissin' contest. [We don't like the selected test method, either.] We believe that our coating thickness spec provides: * Solderability level that we seek. * Repeatable test. * Measurement that board fabricators routinely use in process control.

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Rich

#6074

Solder wetting test for PCB's | 24 April, 2001

Thank you for the input

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Steve

#6077

Solder wetting test for PCB's | 24 April, 2001

Take a look at J-STD-003, Solderability Tests for Printed Boards. This may help you create a procedure.

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Non-heated dispensing system

 Reflow System