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!
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 ?
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