Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Washing boards with paste...?

Larry Johnson

#14297

Washing boards with paste...? | 14 September, 1998

Our company currently donesn't have any type of sonic wash to wash boards that have been "miss printed" Wanting to know the best way to go about this. So what we are having to do is spray down the boards with alcohol and wipeing the solder paste off. This doesn't seem to be a very good method. Please post any ideas that you have... thanks.. larry j

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Wayne Bracy

#14305

Re: Washing boards with paste...? | 14 September, 1998

| Our company currently donesn't have any type of sonic wash to wash boards that have been "miss printed" Wanting to know the best way to go about this. So what we are having to do is spray down the boards with alcohol and wipeing the solder paste off. This doesn't seem to be a very good method. Please post any ideas that you have... thanks.. | larry j Larry: What type of system are you using to clean your stencils? It is possible with certain systems to also clean misprinted PCB's. Take a look at AAT Austin American Technology Corp. They manufacture stencil and board cleaning equipment.

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Ben Salisbury

#14304

Re: Washing boards with paste...? | 14 September, 1998

| Our company currently donesn't have any type of sonic wash to wash boards that have been "miss printed" Wanting to know the best way to go about this. So what we are having to do is spray down the boards with alcohol and wipeing the solder paste off. This doesn't seem to be a very good method. Please post any ideas that you have... thanks.. | larry j Well Larry...you're right...it isn't a very good method, we too use it. If you stay using it, I highly recomend going with the ultrasonic, the few times I've been able to borrow another departments cleaner, it's worked like a charm. A few helpfull hints.... hit the solder when it's still wet, don't let it dry up on the boards, and use 80+ PSI to get the remaining paste out of the score marks, vias, and between fine pitch pads. Check the boards under a microscope to make sure you got it all....and worse case, hey, you can always clean off the Solder balls...heh. -Ben

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Bill Schreiber

#14301

Re: Washing boards with paste...? | 14 September, 1998

Dear Larry, I developed the ultrasonic cleaning process for Smart Sonic. It has developed into the most widely used stencil and misprinted PCB cleaning process worldwide. With that in mind, I offer some words of caution. "IT'S NOT THE ULTRASONICS!" The most important part of any cleaning process is always the chemistry. We use the ultrasonics to deliver our chemistry into the fine-pitch apertures of a stencil and tight vias of a misprinted SMT assembly because "sprays" cannot reach into these areas. Cleaning solder paste without the correct chemistry would be like trying to wash oil from your hands without using soap. The ultrasonic cavitation is just a scrubbing action. You need a chemistry (soap) to go with it. Another word of caution is never use alcohol (or any chemical wipe) to preclean a board or stencil. Alcohol is a very reactive chemistry that can react with the solder paste which can make it more difficult to clean. This is particularly true of no-clean type solder pastes. If you are using a no-clean paste, you may have noticed that the solder paste turns "jelly-like" when coming in contact with alcohol. Our 440-R SMT Detergent can still clean this "jelly", but it does take longer than if no alcohol was used. Just mechanically remove the excess solder paste from the misprinted board or stencil by using a squeegee blade or other device and let the chemistry in the ultrasonic bath do the rest. Visit our Web Site, www.smartsonic.com, and click on the button labled "Recommended Reading." It offers some good information from an industry expert. If you should have any questions, please do not hesitate to contact me. My Tel., fax and e-mail info is listed on our web page. Regards, Bill Schreiber | Our company currently donesn't have any type of sonic wash to wash boards that have been "miss printed" Wanting to know the best way to go about this. So what we are having to do is spray down the boards with alcohol and wipeing the solder paste off. This doesn't seem to be a very good method. Please post any ideas that you have... thanks.. | larry j

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Jeff Sanchez

#14302

Re: Washing boards with paste...? | 14 September, 1998

| Dear Larry, | I developed the ultrasonic cleaning process for Smart Sonic. It has developed into the most widely used stencil and misprinted PCB cleaning process worldwide. With that in mind, I offer some words of caution. "IT'S NOT THE ULTRASONICS!" | The most important part of any cleaning process is always the chemistry. We use the ultrasonics to deliver our chemistry into the fine-pitch apertures of a stencil and tight vias of a misprinted SMT assembly because "sprays" cannot reach into these areas. Cleaning solder paste without the correct chemistry would be like trying to wash oil from your hands without using soap. The ultrasonic cavitation is just a scrubbing action. You need a chemistry (soap) to go with it. | Another word of caution is never use alcohol (or any chemical wipe) to preclean a board or stencil. Alcohol is a very reactive chemistry that can react with the solder paste which can make it more difficult to clean. This is particularly true of no-clean type solder pastes. If you are using a no-clean paste, you may have noticed that the solder paste turns "jelly-like" when coming in contact with alcohol. Our 440-R SMT Detergent can still clean this "jelly", but it does take longer than if no alcohol was used. Just mechanically remove the excess solder paste from the misprinted board or stencil by using a squeegee blade or other device and let the chemistry in the ultrasonic bath do the rest. | Visit our Web Site, www.smartsonic.com, and click on the button labled "Recommended Reading." It offers some good information from an industry expert. | If you should have any questions, please do not hesitate to contact me. My Tel., fax and e-mail info is listed on our web page. | Regards, | Bill Schreiber | | Our company currently donesn't have any type of sonic wash to wash boards that have been "miss printed" Wanting to know the best way to go about this. So what we are having to do is spray down the boards with alcohol and wipeing the solder paste off. This doesn't seem to be a very good method. Please post any ideas that you have... thanks.. | | larry j Bill, Is there any way Larry might be able to use flux thinner that is specifically designed for the flux type that is in his paste to wash his boards.I ask not only for larry but myself. It would seem to me that this would solve the gelling effect that the alcohol has on the paste? However it would not help those hard to get places. Though I agree that a cleaning tank is the way to go! But my cleaning tank is not big enough for every kind of board I build. So If Larry has no cleaning tank in sight from the bean counters above than is this a viable option. Than maybe he can wash his boards with alcohol afterwards? Provided it's the same used in his flux. Thanks ......Jeff

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Dave F

#14299

Tank Cleaning Of Stencils & Boards | 14 September, 1998

| Our company currently donesn't have any type of sonic wash to wash boards that have been "miss printed" Wanting to know the best way to go about this. So what we are having to do is spray down the boards with alcohol and wipeing the solder paste off. This doesn't seem to be a very good method. Please post any ideas that you have... thanks.. | larry j Users Of Tanks To Clean Stencils & Boards: Please help me understand how your process works: 1 What do you do before you tank clean a board or stencil? For instance, do you wipe the majority of the paste from the board or stencil? 2 Do you use a spray wand? How is it "set-up?" 2a What else do you use? 3 Do you use water or someother chemical for cleaning? 3a If something else, what? 4 After washing, what additional processing do you do with the board or stencil? 5 What do you do with the cleaning agent (ie, water, chemical, what ever) after cleaning the board or stencil? 5a How do you periodically clean the tank? What other periodic maintenance do you do on this process? 6 How do you get solder balls out of vias? 6a How do you check the cleanliness of stencil aperatures? 7 What do you do that I didn't ask about in this cleaning process? Thanks Dave F

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Bill Schreiber

#14303

Re: Washing boards with paste...? | 15 September, 1998

Jeff, The use of flux thinner would only add another chemical to the process. Environmentally, that would not be a good idea. My guess is that you would only end up with "thinner jelly" anyway. Alcohol works well on RMA flux. When assemblers switch from RMA to no-clean flux, they assume that alcohol will work as well. Alcohol is NOT a good solvent for cleaning most no-clean and OA solder pastes. Because of it's combustability and explosive hazard, it cannot be used in an ultrasonic tank (nor should it be used inside a spray chamber - reports of explosions involving stencil cleaners using alcohol really scare me). You're right, ultrasonic tanks can be expensive. However, keep in mind, when cleaning misprinted PCBs, you only need an ultrasonic tank half as large as your largest board. You can always clean the misprint one half-at-a-time (with the correct chemistry). Best regards, Bill Dear Larry, | | I developed the ultrasonic cleaning process for Smart Sonic. It has developed into the most widely used stencil and misprinted PCB cleaning process worldwide. With that in mind, I offer some words of caution. "IT'S NOT THE ULTRASONICS!" | | The most important part of any cleaning process is always the chemistry. We use the ultrasonics to deliver our chemistry into the fine-pitch apertures of a stencil and tight vias of a misprinted SMT assembly because "sprays" cannot reach into these areas. Cleaning solder paste without the correct chemistry would be like trying to wash oil from your hands without using soap. The ultrasonic cavitation is just a scrubbing action. You need a chemistry (soap) to go with it. | | Another word of caution is never use alcohol (or any chemical wipe) to preclean a board or stencil. Alcohol is a very reactive chemistry that can react with the solder paste which can make it more difficult to clean. This is particularly true of no-clean type solder pastes. If you are using a no-clean paste, you may have noticed that the solder paste turns "jelly-like" when coming in contact with alcohol. Our 440-R SMT Detergent can still clean this "jelly", but it does take longer than if no alcohol was used. Just mechanically remove the excess solder paste from the misprinted board or stencil by using a squeegee blade or other device and let the chemistry in the ultrasonic bath do the rest. | | Visit our Web Site, www.smartsonic.com, and click on the button labled "Recommended Reading." It offers some good information from an industry expert. | | If you should have any questions, please do not hesitate to contact me. My Tel., fax and e-mail info is listed on our web page. | | Regards, | | Bill Schreiber | | | Our company currently donesn't have any type of sonic wash to wash boards that have been "miss printed" Wanting to know the best way to go about this. So what we are having to do is spray down the boards with alcohol and wipeing the solder paste off. This doesn't seem to be a very good method. Please post any ideas that you have... thanks.. | | | larry j | Bill, | Is there any way Larry might be able to use flux thinner that is specifically designed for the flux type that is in his paste to wash his boards.I ask not only for larry but myself. It would seem to me that this would solve the gelling effect that the alcohol has on the paste? However it would not help those hard to get places. Though I agree that a cleaning tank is the way to go! But my cleaning tank is not big enough for every kind of board I build. So If Larry has no cleaning tank in sight from the bean counters above than is this a viable option. Than maybe he can wash his boards with alcohol afterwards? Provided it's the same used in his flux. | Thanks ......Jeff

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Wayne Bracy

#14300

Re: Tank Cleaning Of Stencils & Boards | 15 September, 1998

| Users Of Tanks To Clean Stencils & Boards: Please help me understand how your process works: | 1 What do you do before you tank clean a board or stencil? For instance, do you wipe the majority of the paste from the board or stencil? | 2 Do you use a spray wand? How is it "set-up?" | 2a What else do you use? | 3 Do you use water or someother chemical for cleaning? | 3a If something else, what? | 4 After washing, what additional processing do you do with the board or stencil? | 5 What do you do with the cleaning agent (ie, water, chemical, what ever) after cleaning the board or stencil? | 5a How do you periodically clean the tank? What other periodic maintenance do you do on this process? | 6 How do you get solder balls out of vias? | 6a How do you check the cleanliness of stencil aperatures? | 7 What do you do that I didn't ask about in this cleaning process? | Thanks | Dave F Dave: sorry for the email, misread your posting..... wayne

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Kevin Ham

#14298

Re: Washing boards with paste...? | 19 September, 1998

| Our company currently donesn't have any type of sonic wash to wash boards that have been "miss printed" Wanting to know the best way to go about this. So what we are having to do is spray down the boards with alcohol and wipeing the solder paste off. This doesn't seem to be a very good method. Please post any ideas that you have... thanks.. | larry j

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