Electronics Forum | Tue Feb 25 06:06:11 EST 2020 | hexton
I am currently weighing up my options for resistors that will be fitted to a fully assembled PCB (PTH&SMT). Do I omit the stencil apertures leaving exposed pads (ENIG) so they can be hand soldered with fresh solder. Considering shelf life for soldera
Electronics Forum | Tue Feb 25 10:30:02 EST 2020 | richardcargill
If you get the stencil made with all apertures included then you can blank some off with sellotape. Saves you buying 2 stencils should you require them machine fitted in the future
Electronics Forum | Tue Feb 25 11:56:33 EST 2020 | slthomas
I think I'd opt for a stencil with everything already cut and then tape it if that didn't screw up your stencil gasketing. Then you just have to define the process for adding the optional parts and you can decide to use those apertures or not.
Electronics Forum | Tue Feb 25 18:36:03 EST 2020 | emeto
Flat surface is the number one choice for fresh part soldering. We did not discuss details about resistor size and location, but to keep them flat I will suggest no apertures on the stencil.
Electronics Forum | Wed Feb 26 07:07:19 EST 2020 | dontfeedphils
"One caveat with ENIG is sometimes washing with hot DI water can effect solderability later on." How so? (Genuinely curious)
Electronics Forum | Tue Feb 25 06:34:50 EST 2020 | hexton
The reason the resistors are fitted at a later stage is to complete the circuit but the values that will be fitted depends on the frequency range desired. My preference would be to leave them free of solder, limiting the options for the process used
Electronics Forum | Tue Mar 03 07:47:48 EST 2020 | dontfeedphils
Thanks for the info. In a past life I ran everything WS and washed in a batch wash using saponifier. I'm surprised I never saw anything then as we would regularly wash boards assembled on only one side. Unless it's specifically washing in DI only.
Electronics Forum | Tue Feb 25 12:15:42 EST 2020 | dwl
Are you running a no clean process, or are you washing your PCBs? One caveat with ENIG is sometimes washing with hot DI water can effect solderability later on. I would also talk to your solder technicians and see what their preference is. Some pr
Electronics Forum | Wed Feb 26 13:26:24 EST 2020 | rgduval
I'd agree with getting a stencil fully cut, and taping the pads you don't want paste on. But, I'd also check with the people that will be doing the hand soldering to see what they prefer. Some people prefer soldering on bare pads, some prefer solde
Electronics Forum | Thu Feb 27 08:59:15 EST 2020 | spoiltforchoice
In both cases, it will depend on storage conditions, unless you do something horrible to them (or as previously mentioned, wash them) months & months. For boards we put through SMT and then stash for THT loading in smaller qty's I don't think we've e
