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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Solder bridging on IC leads

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#62505

Solder bridging on IC leads | 21 August, 2010

I have a problem with solder bridging between IC leads, especially fine pitch leads. If we lessen the apature ratio and/or decrease stencil thickness, I have more of a chance for unsoldered or insufficent joints. I am looking for any information that will help reduce or eliminate solder bridging on IC leads. Thank you!

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#62512

Solder bridging on IC leads | 23 August, 2010

Possible route causes of bridging on fine pitch ICs are; too much paste (stencil aperture wrong), poor print quality (paste smudges during printing), pcb pads not flat depending on the solderable coating, paste has poor cold slump properties, too much component placement pressure smudges pastes, wrong reflow profile makes paste hot slump / paste has poor hot slump properties. To help further we need to know... What is the pcb pad coating ? What is IC pitch and pad size? What stencil thickness / aperture size are you using ?

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#62516

Solder bridging on IC leads | 23 August, 2010

Under a scope, make sure the PCB has soldermask between pads.

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#62517

Solder bridging on IC leads | 23 August, 2010

Similar to Coop's comments, above ...

Bridging: * Mis-placement: misplaced components, high placement force mushrooms paste * Too much paste: HASL thickness, lead finish, poor underside support, poor underside wipe frequency, printing with too large a snap-off, poor stencil design / manufacture, board warp, poor stencil gasketing, high squeegee down-force * Paste slump: paste quality, too much time between print and reflow, poor reflow profile * Misprinted paste

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#62518

Solder bridging on IC leads | 23 August, 2010

SAG: Questions on solder mask webbing with fine pitch parts are: * What is the minimum pitch that you can use webbing between fine pitch pads? * What solder mask do you use?

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#62590

Solder bridging on IC leads | 1 September, 2010

Solder mask between pads in case of fine-pitched device footprint may not be a practical solution to implement.

Cheers !!!

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SMT Equipment

SP700avi inline stencil printer