Stencil - electropolished or not - Page 1
Forum section: electronics / general

author: hcglitte
author_rank: Regular Contributor
timestamp: April 13, 2017, 02:57:55 pm
content: Anyone got hands-on experience with both electropolished and without?I use GC 10 paste, 0.12 mm stencil, QFN, 0402, and have never tried without electropolishing...Would be interesting to see if the paste release will be noticeable...

author: TJ232
author_rank: Frequent Contributor
timestamp: April 13, 2017, 04:10:21 pm
content: From my own experience:- for 0805 and above : can be without.- QFN, 0402, 0.5mm and down, better to have it. Sometime was forced to work with cheap stencils ( 1-2 test demo and proof of concepts boards mostly) and it was a huge pain in the ass.By the way, GC10 is a very good pasteA real beauty if proper mixed just before usage.

author: rx8pilot
author_rank: Super Contributor
timestamp: April 13, 2017, 04:36:28 pm
content: I am a big believer in electro polish for those sizes. Also, consider rounding corners of apertures to encourage paste release if you don't already.In general - I think that with small parts, any skimp in stencil printing is more costly than the savings. Even a 1% failure will likely cost more in re-work than the upgraded stencil.

author: hcglitte
author_rank: Regular Contributor
timestamp: April 13, 2017, 09:47:56 pm
content: Thanks, will continue with electropolishing then. Rework is a pain in the butt.TJ232: Do you have any specific procedure on how you mix it? Personally I take my knife and stir the mix for about 5 to 10 seconds.I received mine in August 2015, and I still use it. I know the rated shelf life is 12 months.I have read somewhere that one way to test the paste is to print some of it on a solder mask area,and if it reflows into one nice ball, it's good (rather than many small particles). I assume this is a wetting test...In my test I have an oversized aperture over a smaller copper circle, and all the solder will go to the copper.

author: TJ232
author_rank: Frequent Contributor
timestamp: April 14, 2017, 07:44:15 am
content: Quote from: hcglitte on April 13, 2017, 09:47:56 pmI am using a small solder paste mixer for uniform viscosity and to properly remove air bubbles.For quick test boards if they have not small fancy footprints, BGA, etc, just using a plastic chemical inert spatula and mix manually for 2-3 minutes the entire solder paste container. When good to go, it will become a liitle bit whitish.If you store it properly (not over 24C and not under 10C) and keep it properly sealed it will last way more than the claimed shelf life.Actually biggest problem for it is to avoid contamination that storage. Do not put back in the container used paste from the stencil. I now GC10 is more expensive than the usual solder paste but if you end up with a 500g contaminated container will be no saving at all. Try to better estimate the dosage for the stencil.

author: rx8pilot
author_rank: Super Contributor
timestamp: April 15, 2017, 06:36:38 am
content: I may try the GC10 paste, it looks excellent. My strategy has been to use 600g tubes and finding them easier to deal with than the jar. The paste is never really exposed to the atmosphere until it is dispensed. The left over on the stencil I put in a small heavy duty zip lock bag and suck the air out. The old gets mixed with the new and I end up with near 100% utilization.Sent from my horrible mobile....

author: mrpackethead
author_rank: Super Contributor
timestamp: April 17, 2017, 11:45:07 pm
content: Im usign GC10 its great. Improved my yeilds consdierably.. Great if yo uare only doing small runs and dont' want to go to all the hassle of managing Solder Paste nicely. Its very very forgiving.Also, unless yoru stuff is huge. Not electropolishing is just trouble.