Electronics Forum | Wed Sep 18 18:48:33 EDT 2002 | davef
Fabs can produce a solder mask web between 20 pitch leads, but I've never seen a web for 16 pitch leads. Although, I would like know a supplier that can lay-down a fine web. Minimum solder mask web width is about 0.004 thou. An absolute mininum o
Electronics Forum | Thu Sep 19 12:08:39 EDT 2002 | ccross
I would like to thank everyone for their time and replies
Electronics Forum | Tue Sep 17 15:03:33 EDT 2002 | ccross
I am working with fine pitch components (15-20 mil) and having soldering problems and would appreciate some opinions. 1) How much of an effect does pad size have on bridging? 2) How much of an effect does solder paste grain size have? What is the re
Electronics Forum | Wed Sep 18 10:06:30 EDT 2002 | Bob M
I place 15-20 mil a lot. You need to look at your pad to apature reduction. Your stencil thickness. The type of paste your using. We use 2-5 mil reduction on each side as a general rule on fine pitch. This varies depending on pad width. We also use 5
Electronics Forum | Wed Sep 18 20:55:33 EDT 2002 | scottefiske
I'm with you dave...please provide specifics as to defect condition... Are you getting good wetting to both land and lead? Is there any repeatability to lead/location/device? Do you have paste inspection capabilites to verify deposition? Is it a Pala
Electronics Forum | Wed Sep 18 06:53:05 EDT 2002 | CH
1) For solder short, pls check the paste height. Too much vol will cause short. For 15 mils use 5 mils thickness stencil if possible. Check profile preheat time to prevent hot slumpof the paste. 2) type 4 powder will be better for 15 mils pit
Electronics Forum | Wed Sep 18 19:43:12 EDT 2002 | dragonslayr
One more variable I've remembered - pad height with respect to solder mask height. Pads being too low can cause stencil "gasketing" problems that in turn allow more paste to be deposited than needed. Are your fabs HASL or some other media?
Electronics Forum | Fri Sep 20 04:47:29 EDT 2002 | byates
If I were you I would contact your solder paste applications engineer and your stencil applications eng. They are there for this very reason and are very capable
Electronics Forum | Wed Sep 18 12:31:16 EDT 2002 | dragonslayr
My suggestion is to conduct a Design For Manufacturing (DFM)study on the assembly in question. Pay particular attention to the pad sizes, component lead dimensions and satisfy yourself that those two factors are correct. Given that pads match compone
Electronics Forum | Wed Sep 18 18:41:17 EDT 2002 | davef
People have made good comments. Additional points are: * Your bridging is probably being caused by one or more of the following: [1] printing too much paste, [2] smearing the paste during placement or subsequent handling, or [3] paste slump during t
