how do the pcba manufacturers clean off the flux after they solder together a board?
is there a way to do it that doesnt require big machinery? sprays that are effective, and that can be used with a populated board?
i have a magazine with a list of chemical sprays to clean the flux off, but not quite sure how to use it properly or the right type that i need...any help appreciated!
thanx
oh and how much can one can clean off?
is there a way to do it that doesnt require big machinery? sprays that are effective, and that can be used with a populated board?
i have a magazine with a list of chemical sprays to clean the flux off, but not quite sure how to use it properly or the right type that i need...any help appreciated!
thanx
oh and how much can one can clean off?
The PCB manufacturers use water based flux... then the boards are cleaned in hot water.
Lacquer thinner and especially acetone are pretty "hot", OK for a quick wipe, but no soaking. They attack plastics, especially PVC (vinyl).
Denatured alcohol can be used any ole way... soaking etc...
Actually tetrachoroethylene (dry cleaning fluid... brake cleaner from the local auto parts store) works great for removing rosin based flux. You can't use it near polycarbonate plastics (Lexan) but these are fairly rare (except some caps) in electronic parts. Like Chris says, watch out for electrolytics, chlorine and lytics don't mix.
Most pots these days are sealed for cleaning, but certainly not all. Switches, pots, caps, and transformers all need special consideration.
Lacquer thinner and especially acetone are pretty "hot", OK for a quick wipe, but no soaking. They attack plastics, especially PVC (vinyl).
Denatured alcohol can be used any ole way... soaking etc...
Actually tetrachoroethylene (dry cleaning fluid... brake cleaner from the local auto parts store) works great for removing rosin based flux. You can't use it near polycarbonate plastics (Lexan) but these are fairly rare (except some caps) in electronic parts. Like Chris says, watch out for electrolytics, chlorine and lytics don't mix.
Most pots these days are sealed for cleaning, but certainly not all. Switches, pots, caps, and transformers all need special consideration.
Assuming nothing like potentiometers or switches to worry about, I soak mine in alcohol (not rubbing alcohol as it has glycerin in it). Denatured alcohol from the paint department of your local home store will work. Soak and scrubb with something like a toothbrush:
VERY IMPORTANT: a partial cleaning is worse than no cleaning as the first material to be removed is the rosin carrier, leaving the corrosive components which will eat away at your metal. So either make it squeaky clean or do nothing.
VERY IMPORTANT: a partial cleaning is worse than no cleaning as the first material to be removed is the rosin carrier, leaving the corrosive components which will eat away at your metal. So either make it squeaky clean or do nothing.
It appears as if many of the pcbs in modern mobile devices (cell phones, wifi cards, gps antennas, etc) are clear coated with some form of protectant against humidity and other abuse/contamination. Perhaps a clear lacquer or epoxy? Most of the benefits of potting, without the heat xfer problems, shrink rates, weight, and cost of a full potting.
Any reason why this couldn't be accomplished by a diy'er? Would there be any benefit?
Any reason why this couldn't be accomplished by a diy'er? Would there be any benefit?
Excellent point BrianL... cleaning is ALL OR NOTHING.
Bluebeard,
No reason why DIYers can't coat their boards. It will make a mess for the guys that are always changing their resistors for faster bass or open midrange.
Coating is good in tropical climates especially... stops rot. In certain circuits, it is a must to control drift. BTW... you don't have to spend a fistful of cash for a good coating. Krylon clear works just dandy. I use it here for products that go in industrial apps. The choice was simple, $14 per can for "electronic" coating, or $4 per can for the same stuff minus the UV tracking dye.
Bluebeard,
No reason why DIYers can't coat their boards. It will make a mess for the guys that are always changing their resistors for faster bass or open midrange.
Coating is good in tropical climates especially... stops rot. In certain circuits, it is a must to control drift. BTW... you don't have to spend a fistful of cash for a good coating. Krylon clear works just dandy. I use it here for products that go in industrial apps. The choice was simple, $14 per can for "electronic" coating, or $4 per can for the same stuff minus the UV tracking dye.
Hi,
Anything I have suggested evaporates quickly. Therefore they are a fire hazard. Do not use in enclosed spaces (ventilate!!).
I have spot cleaned flux from boards many times with no trouble. You will find that a cotton swab tends to take the flux with it. More than one treatment may be required.
I don't soak my boards, I just clean the solder side and use cotton swabs near components that don't like cleaners. I can't agree with the statement that you clean all or nothing. 'Tan't true folks!
Having said that, I approach cleaning test equipment completely differently. What I've said is valid for consumer audio.
Coating boards is valuable for items in environments in corrosive atmospheres and areas that reach or exceed the dew point. It is a pain to work on afterwards, so normally you don't want to do this. I have lots of stuff I built in the 70's that still works fine. The boards look good too.
-Chris
Anything I have suggested evaporates quickly. Therefore they are a fire hazard. Do not use in enclosed spaces (ventilate!!).
I have spot cleaned flux from boards many times with no trouble. You will find that a cotton swab tends to take the flux with it. More than one treatment may be required.
I don't soak my boards, I just clean the solder side and use cotton swabs near components that don't like cleaners. I can't agree with the statement that you clean all or nothing. 'Tan't true folks!
Having said that, I approach cleaning test equipment completely differently. What I've said is valid for consumer audio.
Coating boards is valuable for items in environments in corrosive atmospheres and areas that reach or exceed the dew point. It is a pain to work on afterwards, so normally you don't want to do this. I have lots of stuff I built in the 70's that still works fine. The boards look good too.
-Chris
Chris,
You're asking for trouble. Either clean absolutely clean or don't mess with it. Anyone who has worked in high reliability electronics (test and measurement equipment, computers, military gear, etc.) knows not to do a half baked job of cleaning. Thems the facts whether you like it or not.
You're asking for trouble. Either clean absolutely clean or don't mess with it. Anyone who has worked in high reliability electronics (test and measurement equipment, computers, military gear, etc.) knows not to do a half baked job of cleaning. Thems the facts whether you like it or not.
Hi Brian,
I understand where your concerns may be, but understand two points I've made.
Firstly I don't immerse the boards I clean. Test equipment or otherwise. The trim pots and capacitors don't take kindly to this. TrimDacs are immune to this. I'm not sure about smt type electrolytic capacitors.
Secondly, I'll quote from a previous statement I made :
I own equipment I've worked on in this manner and have never had a problem. When I finish working, it looks like I was never there. That's the best compliment I can receive.
The guys at Fluke or HP have never commented badly about my workmanship or board cleanliness. The same thing goes for consumer gear I've worked on. That's one way they know I've done the job for sure.
I refuse to clean up some else's mess if I'm not getting paid to do so. In those cases I'll clean where I've been and leave the rest. It's come down to that.
-Chris
I understand where your concerns may be, but understand two points I've made.
Firstly I don't immerse the boards I clean. Test equipment or otherwise. The trim pots and capacitors don't take kindly to this. TrimDacs are immune to this. I'm not sure about smt type electrolytic capacitors.
Secondly, I'll quote from a previous statement I made :
I own equipment I've worked on in this manner and have never had a problem. When I finish working, it looks like I was never there.
That's the best compliment I can receive.The guys at Fluke or HP have never commented badly about my workmanship or board cleanliness. The same thing goes for consumer gear I've worked on. That's one way they know I've done the job for sure.
I refuse to clean up some else's mess if I'm not getting paid to do so. In those cases I'll clean where I've been and leave the rest. It's come down to that.
-Chris
You have an intelligent question, Clipped, but there is no easy answer.
In the old days we used Freon, and it was good! Real companies used special cleaning machines using Freon that made the boards virtually clean as can be. Today, there is no Freon.
Now we have to use denatured isopropyl alcohol with a toothbrush, and even this is problematic. Even if we use acetone or commercial flux removers, be VERY careful! IF you have ANY polystyrene, or polycarbonate caps, you can be in big trouble with the stronger cleaners. They will destroy the caps. Trust me, I have had board cap failures traced back to a tech who disregarded this advice. Especially, small polystyrene caps (by the way the best of the best).
Even if you use alcohol, water, (with some solder fluxes) or whatever, use a can of compressed air to blow off the liquid remaining on the surface after application. If you don't, it will just evaporate and leave the sticky stuff behind.
By the way, I have found that removing the physical residue with a steel pick is easy and removes most of the stuff, before you spread it all over the rest of the board.
In the old days we used Freon, and it was good! Real companies used special cleaning machines using Freon that made the boards virtually clean as can be. Today, there is no Freon.
Now we have to use denatured isopropyl alcohol with a toothbrush, and even this is problematic. Even if we use acetone or commercial flux removers, be VERY careful! IF you have ANY polystyrene, or polycarbonate caps, you can be in big trouble with the stronger cleaners. They will destroy the caps. Trust me, I have had board cap failures traced back to a tech who disregarded this advice. Especially, small polystyrene caps (by the way the best of the best).Even if you use alcohol, water, (with some solder fluxes) or whatever, use a can of compressed air to blow off the liquid remaining on the surface after application. If you don't, it will just evaporate and leave the sticky stuff behind.
By the way, I have found that removing the physical residue with a steel pick is easy and removes most of the stuff, before you spread it all over the rest of the board.
Hi John,
Great advice. That's why I do not wash the component side. I may spot clean if needed (with Q-tips the take away the residue).
I think some water soluble flux types are or can be conductive. I've tried them and didn't care for them too much. I stuck with the "old" types.
A friend of mine still runs a consumer electronics service shop. He likes to be ahead of the curve on most things and used - water soluble flux. He had one heck of a time with returns for a bit (he is a busy shop). He has since figured out the solder and flux residue was conductive. You have to get every trace of it off the board. Can you imagine the cost of reworks, and the cost to the customers who have yet to have a failure and connect it with his work? Massive costs that will exceed the cost of normal flux cleanup for some time to come. Actually, I believe the cost will never be covered compared to the normal solvents I buy at his use levels.
-Chris
Great advice. That's why I do not wash the component side. I may spot clean if needed (with Q-tips the take away the residue).
I think some water soluble flux types are or can be conductive. I've tried them and didn't care for them too much. I stuck with the "old" types.
A friend of mine still runs a consumer electronics service shop. He likes to be ahead of the curve on most things and used - water soluble flux. He had one heck of a time with returns for a bit (he is a busy shop). He has since figured out the solder and flux residue was conductive. You have to get every trace of it off the board. Can you imagine the cost of reworks, and the cost to the customers who have yet to have a failure and connect it with his work? Massive costs that will exceed the cost of normal flux cleanup for some time to come. Actually, I believe the cost will never be covered compared to the normal solvents I buy at his use levels.
-Chris
Oh yeah,
The water based stuff is conductive...
We are confusing the issue a bit here though. Repairing boards and building boards is two different things...
When you are bulding up an entire board from scratch, and you are 100% SURE that EVERY component is "process sealed", it is hard to beat a water based system for cost and ease. The fluxes stink like hell though.
Repairs are a different story though... I would opt for the pick and Q tip method myself. Immersing a board with so many unknowns, in ANYTHING, seems nuts.
The water based stuff is conductive...
We are confusing the issue a bit here though. Repairing boards and building boards is two different things...
When you are bulding up an entire board from scratch, and you are 100% SURE that EVERY component is "process sealed", it is hard to beat a water based system for cost and ease. The fluxes stink like hell though.
Repairs are a different story though... I would opt for the pick and Q tip method myself. Immersing a board with so many unknowns, in ANYTHING, seems nuts.
ok guys, i'll sum things up
i want to populate a new board with components, all hand soldered.
will the transistors, ic, opamps, fets, to-220 rectifying diodes be ok if they come into contact with acetone/flux remover/alcohol?
or should i avoid making contact?
think carburetor cleaner would work? its a nice powerful stream of pressure lloks like i should invest in some source of compressed air...
i always thought flux was mildy conductive, is it ? or have i been overly paranoid?
i want to populate a new board with components, all hand soldered.
will the transistors, ic, opamps, fets, to-220 rectifying diodes be ok if they come into contact with acetone/flux remover/alcohol?
or should i avoid making contact?
think carburetor cleaner would work? its a nice powerful stream of pressure
lloks like i should invest in some source of compressed air...i always thought flux was mildy conductive, is it ? or have i been overly paranoid?
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