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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


checking QFP's for opens

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#36623

checking QFP's for opens | 13 September, 2005

I couldn't find any sanctioned procedure for dragging a pick across the leads to check for opens. I've never been a big fan of this anyways. Other than visually inspecting under a microscope and touching the leads that look suspect is there anything that can be done. I think the best is to make sure the oven profile and other factors are set up so as to avoid any opens in the first place.

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#36624

checking QFP's for opens | 13 September, 2005

"I think the best is to make sure the oven profile and other factors are set up so as to avoid any opens in the first place."

I think you answered your own question.

The difficulty (from my limited experience, anyway) in adequately qualifying your process lies first in identifying everything that you have to control....program selection, stencil washing, paste control, bare board quality, etc., then getting the resources to control it all.

Edited to add that if you have problems and decide you need to inspect everything, a microscope is a much safer method. If you feel like you must poke and prod, do it under a scope, limit it to suspect joints and be prepared to touch up (not a good thing in and of itself) every one of them.

We had a problem once at my last employer and it became the normal process to drag solder all 4 sides of every (there were 12) QFP 100 after reflow, on every board....with an OA flux. A new layout, a couple iterations of stencil design, and a new printer later, we stopped drag soldering. I won't tell you what happened when we had washer problems.

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#36625

checking QFP's for opens | 13 September, 2005

oops.

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Essemtec Fox Compact Automatic Pick and Place

soldering station