Electronics Forum: surface tension (Page 6 of 30)

Component Skew during Reflow Process

Electronics Forum | Thu Aug 01 11:43:57 EDT 2019 | slthomas

I noticed that your solder mask registration is off some. Does it cover a significant portion of any of the pads for these parts? If so, is it possible that the surface tension of the solder at liquidus is enough to skew the part when the solder i

Wave solder question

Electronics Forum | Tue Feb 19 15:59:55 EST 2002 | pjc

Surface tension is a likely cause. Surface tension is a negative wetting force. You may have a solderability problem. Be sure your flux is properly activated according to the flux mfg. top side board temp. specification. When surfaces to be soldered,

Surface Tension vs Part Mass

Electronics Forum | Tue Sep 12 07:15:33 EDT 2006 | bwet

I have a thought question for you SMT process engineers out there. We are attempting to have a part selectively drop off in a reflow oven on a 2-sided l-f SMT assembly. In order for this to happen we will have to make sure during the reflow cycle th

Re: What exactly is an apect ratio?

Electronics Forum | Wed Oct 11 16:24:35 EDT 2000 | John Thorup

Hello Antonio ASPECT RATIO = the ratio of one dimension to another as in the ratio of the thickness of a stencil to the width of the aperture. For instance, a 10 mil aperture in a 5 mil stencil will have an aspect ratio of 2. This is aperture width

Re: Calcutating Surface Tension

Electronics Forum | Thu Oct 26 14:40:12 EDT 2000 | ptvianc

Hello: I have not seen a published formula for calculating the package weight that can be secured by molten solder. I have seen forumlas printed for tombstoning. From that aspect, we developed the following rule-of-thumb for first-order estimates:

QFP solder paste volume

Electronics Forum | Fri May 21 15:50:41 EDT 1999 | John Thorup

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

Skewed transistors

Electronics Forum | Mon Apr 21 16:39:50 EDT 2003 | k_h

You might try reducing your solder paste volume. To much solder paste gives the part a pool to float in, nullifying the positive effect of surface tension. I use an aperture on stencil for the heat sink which is 5mils reduced on each side and a 25mil

solderability and hasl thickness

Electronics Forum | Thu Sep 11 16:50:18 EDT 2003 | davef

Sure it's conceivable that thin HASL can cause tombstoning. Harkening back to the ample discussion in the fine SMTnet Archives, tombstoning is caused by an imbalance in solder surface tension between the two pads of SMT component. The source of thi

Wave Solder Balls, VOC-Free Flux, and Glossy Mask

Electronics Forum | Tue Oct 03 18:41:16 EDT 2006 | C.K. Flip

With recent implementation of VOC-Free flux in our shop, we've experienced little solder fines/balls on the above combo of VOC-Free, Water Based, and glossy to semi-glossy mask finish on PCB's. The solder balls show up on close conductor spacings, ~

Solder not reflowing properly

Electronics Forum | Thu Aug 28 08:43:56 EDT 2008 | rgduval

You wouldn't think that placement would affect dewetting or solderability....I wouldn't have either, until it was the only thing left in our process, and when we changed it, things got better. I couldn't begin to explain why, either. The only concl


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