Electronics Forum | Mon Mar 19 14:24:30 EDT 2007 | jdengler
I have been involved with the evaluation of close to a dozen pastes from 5 manufactures. I never found one that would rest on a board for anything close to 24 hrs and still have acceptable performance. Jerry
Electronics Forum | Thu Mar 29 08:58:06 EDT 2007 | chrissieneale
Started measuring rework last week - on some of the boards we are looking at a shocking 20% right first time yield. The paste thing has to be fixed as it's being left more than four hours. Thanks for all the comments - Will let everyone know the re
Electronics Forum | Mon Mar 19 06:47:36 EDT 2007 | chrissieneale
After a little investigation (with my eyes closed and fingers crossed) how about up to 24 hours?! ?! I think i might have found one of the root causes of my oooooodles of rework.
Electronics Forum | Thu Mar 15 09:11:06 EDT 2007 | jdengler
Chrissie, This varies widely by paste, room temperature, and humidity. You would need to do a DOE for you exact set-up. Since you say the room is uncontrolled you need to keep in mind that time will drop as temperature goes up. Different pastes re
Electronics Forum | Mon Mar 19 12:25:11 EDT 2007 | slthomas
This test nicely demonstrates the bond between parts and paste over time, but what about tack of paste on unpopulated boards? It seems she would also need to be testing by placing parts on boards that have been printed for 15 minutes, 30, 1 hour, 2
Electronics Forum | Thu Mar 15 07:04:59 EDT 2007 | chrissieneale
Hello Just wondering if anyone has done trials on how long you can leave paste (tin-lead or pb free) on a board after you have printed it before it starts going 'off'? Thanks Chrissie FYI - have searched and found the 'pasting ahead' thread - jus
Electronics Forum | Fri Mar 16 07:16:35 EDT 2007 | chrissieneale
Thanks for that - i now have a starting point! Always the hardest bit. I'll report what i find! Chrissie
Electronics Forum | Fri Mar 16 06:36:35 EDT 2007 | realchunks
Hi Chris, You should check your data sheet from the paste manufacturer, but the bottom line is, does this wait step cause any quality problems? If not, then it's a hard argument to say this is a bad practice. Next you may want to find out why th
Electronics Forum | Thu Mar 29 09:11:23 EDT 2007 | slthomas
chrissie, at my last place of employment the reason they did it was so they could print the last of a lot, then change over the printer and start printing up for the next lot and have some ready to go when they finished changing over the chip shooter
Electronics Forum | Fri Apr 06 01:46:59 EDT 2007 | Haris
Basically its spec. gives surety regarding its chemical and physical properties. if he doesnt follow the spec then may be he may find good physical soldering appearance but chemically it may goes down through Electrical or Environmental testing and i
