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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


printing solder paste on test vias

#25561

printing solder paste on test vias | 21 August, 2003

For ICT purposes I may need to print solder paste on 0.015" test vias. No-clean is not an option for this assembly and OA seems the only choice. Can flux be safely removed from inside the via from the other side during a standard water wash process? Worst case: what if the vias are solder mask pluged on the opposite side? In either scenario, is this a reliability issue(if OA flux remains in the via)? It seems unlikely a wash will remove all flux??

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mantis

#25562

printing solder paste on test vias | 22 August, 2003

Kenny, Out of curisoty why do you need to paste the vias.Is it due to contact reliability at test.Can these vias not be soldered during wave process (if any).Can the Style of probe used in the ICT test fixture not be changed to accomodate these unsoldered vias? Regards,

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#25565

printing solder paste on test vias | 22 August, 2003

Mantis: Kenny reflows paste on [wave solders] all via, not just the test via, to plug the via and provide for a pressure seal between the board and the test fixture. Beyond that, since solder is softer than copper [and fills the hole better], solder give better probe life.

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#25566

printing solder paste on test vias | 22 August, 2003

Kenny: Since you need to use water soluable flux and can't use no-clean, consider asking your board fabricator to plug the via.

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iman

#25593

printing solder paste on test vias | 26 August, 2003

depends if your water wash process is manual or automation? important is the water residue inside the via holes is adequately blown out. As long as the water-flux residue is out, testing down the line should not be a issue, at least from theory and our own experiences tell.

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