How to protect your PCB?

[Peter_wadley]

Hey there,

I've been reading up on PCB protection.. I would like to try protect one of my boards this weekend.. so instinctively Im seeking opinions!

Im looking for a chemical that I can spray or coat onto the BOTTOM of the PCB (The side which has the tracks and solder connections)

Im looking to protect the solder from oxidation but more importantly Id like to insulate the tracks..

Something Rubber that can be handled by sweaty human hands is top priority.

I went to the MG website and found these two chemicals - are they what im looking for?

https://www.mgchemicals.com/products/422a.html

*Id really like to know if this one ^ (Silcone) is what im looking for.. my local electronics store carries it.

or

**broken link removed**

Will the FLUX of the solder interfere with the bonding?

Thanks for your opinions, they mean alot.

 

[dknguyen]

All conformal coatings insulate the tracks (After all...they couldn't be conductive now can they!) and protect from oxidation (since they cover the thing...it's pretty obvious). Silicone coatings are often used so that traces on a board can be placed closer together and not arc. Yes, flux will interfere with the bonding. It must be cleaned.

MG chemicals also has acrylic conformal coating. I use silicone as it is the most flexible and withstands higher temperatures than acrylic but can be removed for repairs (unlike urethane which produces toxic vapours when you burn through it with a soldering iron). THe only real reason for using urethane is acid resistance since it is harder (more component stress), less temperature resistantm and harder to rework than silicone. Acrylic is just a cost thing over silicone and also matches urethane in everything except acid (Generally speaking, you can google and find alot more about urethane vs silicone conformal coatings). Unless I'm mistaken urethane is better at that than silicone. But silicone is easy to work, rework and flexible. 2000V/mil dielectric strength is probably enough insulation (urethane is highest at 2650V/mil according to MG chemicals).

Of course, the chart actually varies in real life- just because moisture resistance is "extreme" doesn't mean they are equal. But if it's large enough to be written differently in such general terms, it's probably a big difference.

Did I also mention that new layers of silicone will bind with prexisting layers? It means you apply multiple coatings allowing each one to dry as well as simple reapplying it to the reworked area. Because of this bonding and it's flexibility you can apply quite thick layers and increase the overall dielectric strength quite a bit (you only have one shot with the others and if you make them too thick in one go they can't cure properly).

 

[mvs sarma]

Poly urethene coat is applied after the assembly is complete. this will gaurd damages to PCB from saline atmospheres near seacoast and from other chemicals. Even a laquer spay will suffice .

If you have to protect the pcb from oxidation prior to population of the same, i feel, a smear of petrolleum jelly is better. as you come to assembly, you may clean it by spirit and go ahead. this type of suggestion my appear misery for some . but at hobby level these concepts do serve the need.

 

[Peter_wadley]

All conformal coatings insulate the tracks (After all...they couldn't be conductive now can they!) and protect from oxidation (since they cover the thing...it's pretty obvious). Silicone coatings are often used so that traces on a board can be placed closer together and not arc. Yes, flux will interfere with the bonding. It must be cleaned.

MG chemicals also has acrylic conformal coating. I use silicone as it is the most flexible and withstands higher temperatures than acrylic but can be removed for repairs (unlike urethane which produces toxic vapours when you burn through it with a soldering iron). THe only real reason for using urethane is acid resistance since it is harder (more component stress), less temperature resistantm and harder to rework than silicone. Acrylic is just a cost thing over silicone and also matches urethane in everything except acid (Generally speaking, you can google and find alot more about urethane vs silicone conformal coatings). Unless I'm mistaken urethane is better at that than silicone. But silicone is easy to work, rework and flexible. 2000V/mil dielectric strength is probably enough insulation (urethane is highest at 2650V/mil according to MG chemicals).

Of course, the chart actually varies in real life- just because moisture resistance is "extreme" doesn't mean they are equal. But if it's large enough to be written differently in such general terms, it's probably a big difference.

Did I also mention that new layers of silicone will bind with prexisting layers? It means you apply multiple coatings allowing each one to dry as well as simple reapplying it to the reworked area. Because of this bonding and it's flexibility you can apply quite thick layers and increase the overall dielectric strength quite a bit (you only have one shot with the others and if you make them too thick in one go they can't cure properly).

Hey guys, Is there a special way to clean the flux.. special chemicals?

I guess I will buy the Silicone comforming spray today and give it a go.

 

[jpanhalt]

Hey guys, Is there a special way to clean the flux.. special chemicals?

I use a mixture (about 50/50 -- not critical) of acetone and ethyl alcohol (denatured, grain, analytical grade, etc.) and an old toothbrush to remove flux. The acetone is probably not required. I add it to make a slightly more aggressive solvent; however, if there are plastic components susceptible to acetome on the board (for example, certain connector types), I omit it. Some people use pure isopropyl alcohol and omit the acetone.

The important thing, I believe, is to avoid water. So, whichever alcohol you use, try to get 100%, not 70% or so. John

 

[Peter_wadley]

I use a mixture (about 50/50 -- not critical) of acetone and ethyl alcohol (denatured, grain, analytical grade, etc.) and an old toothbrush to remove flux. The acetone is probably not required. I add it to make a slightly more aggressive solvent; however, if there are plastic components susceptible to acetome on the board (for example, certain connector types), I omit it. Some people use pure isopropyl alcohol and omit the acetone.

The important thing, I believe, is to avoid water. So, whichever alcohol you use, try to get 100%, not 70% or so. John

Hey there,

Alright I shall try rubbing alcohol w/ a toothbrush.

Thank you for the tip

 

[Peter_wadley]

Hey there,

Alright I shall try rubbing alcohol w/ a toothbrush.

Thank you for the tip

Works like a charm. Much Thanks!

 

[Rolf]

What type of environment?

Hey there,

Alright I shall try rubbing alcohol w/ a toothbrush.

Thank you for the tip

Peter,
now that you have found out how to clean the rosin of your boards; what are you trying to protect them from?
My PIC programmer gets banged around on my desk among all kinds of stuff, so I hot glued a piece of PVC plastic to it, same size as the board, works great.
I think the silicone is an overkill, unless you are trying to protect it from moisture in the tropics. Most any paint or lacquer type of spray would give an adequate coating, under most circumstances. But most are not good for metal because of their poor adhesion.
If you need aberration resistance and good adhesion then an epoxy type paint might be prudent. About the only type in a spray can is called Appliance Epoxy Paint.
Warning: I have not tested it for dielectric properties.

 

[3v0]

My PIC programmer gets banged around on my desk among all kinds of stuff, so I hot glued a piece of PVC plastic to it, same size as the board, works great.

Along the same line.

You can also go the old school route and mount the board to a small block of wood on standoffs. It give the board a bit weight too.

 

[Peter_wadley]

Yes physically attaching a substrate seems to work just as good.

I just sprayed the board with MG Silicone comforming spray coating. Hopefully it dries soon (Supposed to bring it to customer today)

Update: Wow this stuff is great! Dried to the touch in 30 minutes.. only needed a tiny tiny amount to insulate! awesome.