Category:PCB Assembly PCB Assembly Service

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In assembly the bare board is populated with electronic components, called a "printed circuit board assembly" (PCBA). In through-hole technology, the component leads are inserted in holes surrounded by conductive pads; In surface-mount technology (SMT), the component is placed on the PCB so that the pins line up with the conductive pads or lands on the surfaces of the PCB.

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QFP solder paste volume Reply 2017-02-28 05:17:35
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rownickijan

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We are running a number of boards with 8-10 25 mil PQFPs on board. Our process is mature with at least 3 years experiance and statistically few opens on the QFPs. Our beloved purchasing department has chased the almighty $ and changed FAB vendors with questionable results. Since the new vendor was properly qualified and the FABs are not technically defective I am stuck with them. The problem ranges from no release to insufficient release on 1 axis caused by HASL height irregularity preventing proper contact and lowering the surface tension to a point where the release is not complete. While the great majority of these boards will print, the paste volume is lower on 1 axis resulting in an unacceptable number of opens. I first thought to increase the stencil thickness from 6 to 7 mil but concluded that this would just exacerbate my surface tension problem. My stencils are electropolished chem etch. Does anyone havea comments about lazer cut stencils with a trapezoidal shape? other suggestions? (other than what to do with purchasing) Thanks
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Statement: This post is only the personal view of the author and does not represent the opinions of ALLPCB.com.

buy

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Helpful!

bruce_baldwin

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I am going to keep checking for new writings.

Turchi Leonardo

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I have learned a lot from your article. Quite useful and impressive info.

Devin

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Really helpful.

Basil

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This post is really interesting.
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