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Water Absorption of PCB

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Stephen- SMT engineer trainee

#47687

Water Absorption of PCB | 15 February, 2007

1. Can anyone tell me about the water absorption(wt%) among different PCB((i) RoHS, (ii)non-RoHS, (iii) Halogen free)), I am currently facing the problems of PCB blisters after reflow process.

2. Also, please suggest the baking period/time among differnt PCB((i) RoHS, (ii)non-RoHS, (iii) Halogen free)).

Very thanks!

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#47690

Water Absorption of PCB | 15 February, 2007

Questions are: * Is the blistering in the solder mask or the laminate? * If the blistering is in the solder mask, what do the blisters look like [eg, size, quantity, distribution, etc]? * If the blistering is in the laminate, what do the blisters look like [eg, size, quantity, distribution, etc]?

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Stephen- SMT engineer trainee

#47857

Water Absorption of PCB | 21 February, 2007

Some of the blister in solder mask, normally 1 circle blister(about 1cm in Dim.) in each PCB.

In addition, there are also blister in laminate, the also look like 1 circle blister(about 1cm in Dim.) in each PCB.

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#47861

Water Absorption of PCB | 21 February, 2007

The cause could be a lot of different things. As long as you didn't use excessive reflow temperatures, we'd guess that: * Solder mask blister: Your board fabricator should be able to demonstrate through TMA [or equivalent] analysis that the mask was cured properly. * Delamination: Could be caused by improper preconditioning to remove entrapped moisture. OR a range of different fabrication issues.

Search the fine SMTnet Archives for recipes to use in removing entrapped moisture. For instance: http://www.smtnet.com/Forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=11222&mc=4

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