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via in smt pad

ben

#27771

via in smt pad | 26 March, 2004

I have recently encountered a new pcb design with a very high density of components on either side of the pcb.

One of the suggested "fixes" is to use the smt pads as vias i.e. the via will be drilled thorough the centre of the smt pad.

My concern is solder leaching creating solder beads/un-soldered joints post reflow.

I have experience of intrusive reflow and suitable stencil design but am unsure of the impact of simply drilling holes through pcbs to free up real estate.

Has anybody experieced a similar issue, and produced IPC class 2 pcb assemblies using this idea or is it just a no go?

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#27775

via in smt pad | 27 March, 2004

Via in pad is a designer's dream and an assembler's nightmare. Search the fine SMTnet Archives for previous discussions to get started.

VIP, via-in-pad, or whatever tend to promote voiding within the via and certainly partially starved solder connections. For desktop, office, telecom, and other relatively benign end-use environments, these conditions are probably OK. In other, more demanding end-use environments they probably are unacceptable.

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#27901

via in smt pad | 3 April, 2004

There is a method for VIP you may not be familiar with. I dont want to go into depth here but check out http://www.sipad.com/sipadvip.htm and contact me off line if you want more info.

Good luck.

mk

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