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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


voids in solder

pzohbon

#5409

voids in solder | 28 February, 2001

I am having problems with voids in our soldering process. I believe it to be the fact that we use a no clean flux without control on how the boards are handled (gloves, procedures, etc.) Does anyone have suggestions on the appropriate place to start?

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#5424

voids in solder | 1 March, 2001

If the soldering process is not controlled, the results are variable, regardless of the flux type.

Tell us more about your concerns, process, solder, etc

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Dason C

#5431

voids in solder | 1 March, 2001

Not enough info, when you say no clean flux, is it for wave soldering process, please provide more detail, SMT or wave, is it all the joint which you find the void?

Rgds

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#5442

voids in solder | 2 March, 2001

Are your voids looking like blow holes also? Is this only occurring on the solder joints of the Thru Hole components and Via's? Or does this happen on SMD pads? My experience is that we have seen this but only with some of our older PCB's which are 90 percent Thru Hole Technology. You have a couple of options of where the problem may be coming from: Moisture in the PCB, incomplete barrel of the PTH's, or moisture in your flux. We have always found that it was due to moisture absorption in the boards. Its because they lay around in a humid environment on shelves unsealed or taken out of the vendor sealed bags. I have found that the best way to test and see if it is moisture in the boards was to take a few assemblies and bake them out. 105 - 115 C for about 90 minutes can remove most of the moisture in the boards. After baking them out run them through your wave and see if the problem disappears or your number of voids are reduced. If not, then it might be the other two cause.

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DALE DOLAN

#5474

voids in solder | 6 March, 2001

Hello I am looking for any data that confirms the long term reliabilty of no clean paste as opposed to water soluable. Does anyone have any past experiences of problems when changing over from water soluable to no clean in the SMT prcocess?? Thanks in advance. Dale.

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#5475

voids in solder | 6 March, 2001

Two things:

1 Go to IPC and buy "TP-1115 - Selection & Implementation Strategy for A Low-Residue No-Clean Process - Provides direction to electronics manufacturers interested in adopting low residue (LR) assembly technology. It addresses the concerns of process engineers and others coming into the field of low-residue processes from two different areas: those who currently clean finished assemblies using water-based, semi-aqueous or other environmentally acceptable solvents and defluxing technologies; or those who use a standard residue-level (SR) no-clean assembly process. Both types of manufacturers should understand the advantages and pitfalls of using low-residue soldering materials. This guide allows electronics manufacturers to choose the process/materials that will best suit their needs. 120 pages. Released December 1998."

2 Find "Evaluation of Low Residue Soldering for Military and Commercial Applications: A Report from the Low-Residue Soldering Task Force" June 1995. I can't find our copy. So, I'm not sure where to send you. Maybe check with Cal at EMPF. It sounds like something they would do.

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CAL

#5478

voids in solder | 6 March, 2001

Are the voids in the balls of a BGA? Are you verifying this through x-ray if they are? some voids depending on size and location are some what accepted.

Solder paste type? Solder paste date code? Humidity high? PCB's been stored in a truck trailer?

just a few questions to help with the problem. Cal www.aci-corp.org www.empf.org

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