Electronics Forum | Thu Jun 16 00:24:29 EDT 2005 | mskler
Hi everybody, Can some body tell me that what stencil thicknes is required for the 16mil QFP. I am getting bridging as well as dry at QFP pins. What type of solder 1. Viscocity 2. mesh size 3. flux contents Should be used for this type
Electronics Forum | Thu Jun 16 08:31:15 EDT 2005 | jh0n!
The most part I have the most difficulty with is a 16mil QFN. We found that reducing stencil thickness to 4mil, and reducing aperatures for the IC by 20%, and setting local fiducials to the IC helped immensely. We used to get 75% or more bridged ou
Electronics Forum | Tue Mar 03 02:39:56 EST 2015 | sarason
I would presume you reflow the top of the board first. Use tented vias. As you have worked out, vias have surface tension, which sucks the solder up the hole during reflow of the bottom of the board. Good luck! regards sarason
Electronics Forum | Tue Mar 03 03:11:57 EST 2015 | vb7007
Hi I also forgot to mention, top side is reflowed first at SMT. Tenting vias is good option. we are looking into it. Can you please also suggest any solution to avoid solder balls at bottom side in other places than vias. Thanks
Electronics Forum | Mon Mar 02 23:48:22 EST 2015 | vb7007
Hi We are using Universal carrier for a 2 sided PCB, where the bottom side goes for hand solder the switches after wave. Our issue is, we are getting micro solder balls all over PCB bottom after wave, whereas we got numerous vias, which also turns
Electronics Forum | Tue Mar 03 09:29:48 EST 2015 | rgduval
A couple of things that have helped me with solder ball issues at wave in the past: 1. Flux. Insure good flux coverage on the bottom of the board. 2. Preheat. Insure that the board is sufficiently preheated for the wave operation. Since you're
Electronics Forum | Thu Jun 16 22:14:51 EDT 2005 | davef
16 thou pitch parts: Use a 5 thou laser cut electropolished stencil with 0.008"x0.045" apertures and type 3 solder paste. Bridges Connecting or Partially Connecting Adjacent Leads or Lands * Excessive solder paste * Excessive component placement pre
Electronics Forum | Mon Aug 23 03:12:57 EDT 2010 | grahamcooper22
Possible route causes of bridging on fine pitch ICs are; too much paste (stencil aperture wrong), poor print quality (paste smudges during printing), pcb pads not flat depending on the solderable coating, paste has poor cold slump properties, too muc
Electronics Forum | Sat Aug 21 15:07:34 EDT 2010 | jry74
I have a problem with solder bridging between IC leads, especially fine pitch leads. If we lessen the apature ratio and/or decrease stencil thickness, I have more of a chance for unsoldered or insufficent joints. I am looking for any information th
Electronics Forum | Mon Aug 23 17:43:18 EDT 2010 | davef
SAG: Questions on solder mask webbing with fine pitch parts are: * What is the minimum pitch that you can use webbing between fine pitch pads? * What solder mask do you use?
