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PCboard potting / enclosure

MrDEB

Well-Known Member
Have a number of circuit boards that are complete and work as desired BUT it is a handheld game that needs an enclosure to protect the Pic.
Tried some Loctite PL construction adhesive on one board but after it cured the project would not work (experiment failed)
Ordered some circuit board potting material and plan to pour only 1/8 - 1/4 inch deep. Remember this is a handheld game
This will then be the "enclosure"
basically killing two birds with one stone.
 

gophert

Well-Known Member
Most Helpful Member
Most polymers shrink as they cure or cool. Even a 0.3 to 1% of shrink creates a huge shear force across a PCB because the shrink happens Even if you think 0.3% is a very small amount. For a 4-inch (100mm) circuitboard, the LEDs on the edge will be displaced by about 0.15mm as the resin shrinks towards the center. Note the FR4 boards do not move much at all because of the glass fiber filling.

Use glass or mica ("mineral") filled potting compounds. There are a few materials with near zero shrink that use a competing physical/chemical effect (similar to zero CLTE alloys).
 

gophert

Well-Known Member
Most Helpful Member
here is what I ordered
never occurred about shrinkage
Have non hardening clay ordered to form a mold box around the PCboard.
epoxies get hot if you pour a thick section. Note the warning from one of the reviewers...
I would suggest that the volume poured is not so important (as the reviewer said) but an issue of the thickest cross-section. I would make multiple pours and keep the first under 4mm and each additional pour 2mm or less. The additional pours should be less because the first pour insulates the following pours.
 

MrDEB

Well-Known Member
plan to just cover the pic and resistors. Will use aprox .03 oz of resin as the Aluminite sites calculator shows.
 

gophert

Well-Known Member
Most Helpful Member
Be careful mixing small volumes, you end up with more on the walls of your container and spatula than you do with the pourable resin.

also, check your math or the calculator, 0.03oz is about 1 gram which is about 1ml. I understood you wanted to cover the whole board to make a box, not just a puddle around one or two components.

you have plenty there for a few trial runs to get the feel of the material before doing the real thing.
 

MrDEB

Well-Known Member
Just want to pour to cover the pic and resistors so 1/16" should do the deed.
I plan to mix enough to cover several boards at one time and using clay to retain the resin within the PCB area,
 

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