Covering solder joints with JB Weld?

[revans]

I've got a pretty weird question at hand...

I've just soldered up a circuit (an LED battery meter for a 12v SLA). It's pretty much the first time I've ever soldered anything more than an led and I ended putting it all on a vero board type thing.

I remember hearing somewhere that solder joints deteriorate over time. My circuit is going to be put somewhere where it probably won't be accessible to resolder/fix/whatever so I was wondering if I could seal my solder joints with J-B Weld to prolong its lifespan as I have some lying round at home. If this will work, great, but if not could somone please suggest an alternative. Thanks.

 

[Leftyretro]

I've got a pretty weird question at hand...

I've just soldered up a circuit (an LED battery meter for a 12v SLA). It's pretty much the first time I've ever soldered anything more than an led and I ended putting it all on a vero board type thing.

I remember hearing somewhere that solder joints deteriorate over time. My circuit is going to be put somewhere where it probably won't be accessible to resolder/fix/whatever so I was wondering if I could seal my solder joints with J-B Weld to prolong its lifespan as I have some lying round at home. If this will work, great, but if not could somone please suggest an alternative. Thanks.

A well made solder joint using the proper tools, materials and methods will most likely out live you. Putting glue over it will not help and probably hurt.

Lefty

 

[revans]

Ha oh well, guess I was misinformed Sorry about the useless question, that's the end of that topic then...

 

[tonigau]

It says it is an electrical insulator so should be ok.

But you shouldnt have to go as far as potting the circuit, What ya gonna do if a fault develops in the circuit, if its potted you have to make another one.
Circuit board laquer is usually adequate for medium environmental exposure, a better conformal coating will give much better environmental protection. For both the thickness & quality of application is significant to final protection.

I see plenty of boards that have been conformal coated but not sprayed properly, resulting in corroded IC pins, copper tracks & thin wave soldered joins.
Corrosion on component legs finds it way the past hermetic seal of just about any part.
A test board I conformal coated is still operating in an open wall shed with spider webs & humidity, has been there since 1997.


The component legs & copper tracks will be susceptible to corrosion more so than solder joins unless the solder is very thin. This is what I observe on field boards in for repair.

TG

 

[Sceadwian]

JB weld is just an epoxy it should be perfectly safe to use as a conformal coating if you expect the environment to be particularly bad. If you do put the epoxy on make sure you clean everything very well and dry the board out well before you seal it. (I'd even go as far as baking it at a low oven temperature like 100 degrees to drive out moisture) Any trapped moisture or debris could hurt things. Mind you JB weld is a pretty good insulator so the temperature your circuit gets up to could be dramatically higher if you cover IC's or transistors.

 

[KMoffett]

JB weld is just an epoxy

J-B Weld is a "metal filled" epoxy.

=====================================================================
INGREDIENTS WGT% CAS # TLV/PEL
Calcium Carbonate 40-50% 1317-65-3 ACGIH: TWA 10 mg/m3
OSHA: PEL 15 mppcf
Iron Powder 10-20% 65997-19-5 ACGIH TLV 15 mg/m3
OSHA: PEL 15 mppcf
Epoxy Resin 30-40% 25068-38-6 N/E
Aromatic Hydrocarbons 1-5 % 64742-94-5 N/E

Though it claims to be an insulator (no indication of breakdown voltage), why would you want to use that rather than normal epoxy?

Ken

 

[Dean Huster]

I agree with Ken. Try using J-B Weld to attach a rare-earth magnet to something and you'll get a big surprise when you watch the epoxy "come alive" and conform to the magnetic field! There indeed is plenty of iron "filings" in that epoxy and I'd never use it in conjunction with an electrical circuit.

If anything, a circuit board can be protected better if it's tin-plated using Tinnit or similar product. The military of the 1960s used a lot of conformal coatings on their PCBs and they were a pain to repair -- failed just as often -- pain to repair. Pick your battles!

Dean

 

[KMoffett]

I agree with Ken. Try using J-B Weld to attach a rare-earth magnet to something and you'll get a big surprise when you watch the epoxy "come alive" and conform to the magnetic field!
Dean

Yeah, ran into that several years ago.

Ken

 

[bigkim100]

Caulk!

I always like using clear bathtub caulking. Cheap, and easy to cut thru for repairs...or just peel off

 

[Sceadwian]

Just because the JBweld has magnetic filings in it doesn't mean it's conductive. The epoxy itself will likely isolate anything that's used as a filler. Drop a blob on a piece of plastic and check it for conductivity with a multimeter if you really want to know. Conductive epoxies aren't that common.

 

[KMoffett]

Just because the JBweld has magnetic filings in it doesn't mean it's conductive. The epoxy itself will likely isolate anything that's used as a filler. Drop a blob on a piece of plastic and check it for conductivity with a multimeter if you really want to know. Conductive epoxies aren't that common.

Agree! But, what's the point of using a "metal filled" epoxy on a circuit board. Maybe on an engine block..or a structural application. But if you need that kind of strength, you're in a whole different ballpark.

Ken

 

[Leftyretro]

Just spray it if you really think you need some kind of protection:

**broken link removed**

 

[Dean Huster]

I've used the clear spray (Krylon) approach often and like it. Fast, it works, easy to repair as a soldering iron pops right through it.

OK. Here's a couple of problems with metal-loaded epoxy for electronics. First, it may be non-conductive, but it won't be as non-conductive as non-metal-loaded versions in that the voltage breakdown of the JB Weld will be lower because you have all these tiny little tie points across the blob: arc-point-arc-point-arc-point-arc-point-arc-point-arc-point-arc. The other problem you can have is with inductive RF circuits. All that iron can detune was was originally a finely-tuned circuit. In other words, if you have a choice, why pick the JB over a non-loaded variety? Having stock in the company would be the only reason and a lousy one at that!

By the way, I am NOT knocking JB Weld. I love the stuff and use it all the time .... but not for all applications.

Dean