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BGA Pad Dressing After Removal Method

Dave F

#15601

BGA Pad Dressing After Removal Method | 3 June, 1998

What methods do people use to dress pads after removing and before replacing the BGA? We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? Dave F

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Earl Moon

#15612

Re: BGA Pad Dressing After Removal Method | 3 June, 1998

| What methods do people use to dress pads after removing and before replacing the BGA? | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | Dave F Dave, What better way? This the world of "rework" that does not exist in my idealistic world of never having to replace anything unless an ECO dictates. Let's get together and invent an air knive or laser broom that does the job without disturbing or destroying adjacent components. Not trying to be flip, Earl

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Dave F

#15613

Re: BGA Pad Dressing After Removal Method | 3 June, 1998

| | What methods do people use to dress pads after removing and before replacing the BGA? | | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | | Dave F | Dave, | What better way? This the world of "rework" that does not exist in my idealistic world of never having to replace anything unless an ECO dictates. Let's get together and invent an air knive or laser broom that does the job without disturbing or destroying adjacent components. | Not trying to be flip, | Earl Earl: We did try using our pneumatic soldering tool, but it was even slower than solder wick. Dave F

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Justin Medernach

#15609

Re: BGA Pad Dressing After Removal Method | 4 June, 1998

| What methods do people use to dress pads after removing and before replacing the BGA? | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | Dave F Dave, Here's one. Why wick? If you are using eutectic spheres. All you are concerned with is rough coplanarity. Jeez, oxymoron. Sorry. What I'm trying to say is that you don't need to remove the solder. You just need to make it all even. Try this yourself. Use a wide tip on your iron. Drag across the pads. NO WICK. Occasionally, you will have to wipe the tip so you will be removing some solder but the point is to make all the pads roughly similar. Then spread Paste Flux. It's very important that you use paste flux. Talk to your paste sales ass. (yuk yuk) You can place a new BGA on top of this and rework. All will be good. The paste flux cleans the spheres / pads and holds the part in place. There will be sufficient solder still on the pads and in the spheres of the BGA to get a reliable solder joint. It's a heck of a lot faster. As for high temp spheres, you're up the creek and you need to take the time unless someone has a better way. Cheers, Justin

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Anthony

#15608

Re: BGA Pad Dressing After Removal Method | 4 June, 1998

Dear Dave, I have a "possible" solution to your problem, though I have never tried it myself. If you're trying to come up with a non-abrasive technique for removing solder-keep reading. If it's a faster method you desire, do yourself a favor and hit the back button right now. The following method I describe is sure to be very meticulous and more expensive than your current process; however, it should prove to be far less risky to the integrity of your pads and neighboring traces and vias. There's a company called Zephyrtronics, located in Southern California, who is in the business of low temperature rework. What they sell is a low temperature "air bath" unit that gets placed underneath the PCB. This air bath unit's output tops out at about 150 degrees C. Now in order for this air bath unit to reflow your solder, you will need to lower the melting point of the solder you wish to remove by placing an alloy of tin, lead, and bismuth at each pad location. Doing this will allow you to perform your rework at temperatures BELOW 150 degrees C. Once all of the solder has become molten, you could use a broom and dustpan type method for removing the solder or a solder sucking device. In the demonstration I saw, they were scooping up the metal with an ordinary sheet of paper. Obviously there are some flaws in using this method. Here are just a few that come to mind: 1.) Cost. I don't remember exactly how much but I believe that a six-inch strip (around there) of this alloy will run you about $10.00. On top of that, I'm not sure how far that will get you. 2.) You probably won't be able to remove 100% of the bismuth, thus slightly changing some of the properties in the solder joints of your newly placed BGA component. 3.) This new alloy, in molten form, reminds me of mercury. If you tip this board during reflow, the little beads are sure to run amuck. So anyway, the point I'm trying to make (and I took my time getting there) is if you're concerned about damaging your PCB while wicking the solder from BGA pads; there is another alternative. If you want further information on this, feel free to contact me either by email or at (909) 734-3001. Good luck! Sincerely, Anthony Hunt

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Terry Burnette

#15607

Re: BGA Pad Dressing After Removal Method | 4 June, 1998

| What methods do people use to dress pads after removing and before replacing the BGA? | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | Dave F We've been using an Edsyn TSX70 Soldavac, for dressing BGA pads, for the last 5 years, and getting good results. The only modification I've made was to bypass Edsyn's vacuum generator, and hook directly into our plants main vacuum line, for the purpose of getting a higher vacuum. Once the transformer died on our Soldavac, and Edsyn had a complete replacement system in my hands within 24 hrs., and never ask for a P.O. Terry Burnette 512-933-5783

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Dave F

#15611

Re: BGA Pad Dressing After Removal Method | 4 June, 1998

| | What methods do people use to dress pads after removing and before replacing the BGA? | | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | | Dave F | Dave, | Here's one. Why wick? If you are using eutectic spheres. All you are concerned with is rough coplanarity. Jeez, oxymoron. Sorry. What I'm trying to say is that you don't need to remove the solder. You just need to make it all even. Try this yourself. Use a wide tip on your iron. Drag across the pads. NO WICK. Occasionally, you will have to wipe the tip so you will be removing some solder but the point is to make all the pads roughly similar. Then spread Paste Flux. It's very important that you use paste flux. Talk to your paste sales ass. (yuk yuk) You can place a new BGA on top of this and rework. All will be good. The paste flux cleans the spheres / pads and holds the part in place. There will be sufficient solder still on the pads and in the spheres of the BGA to get a reliable solder joint. It's a heck of a lot faster. As for high temp spheres, you're up the creek and you need to take the time unless someone has a better way. | Cheers, | Justin Justin: Good idea!! Dave F

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Dave F

#15610

Re: BGA Pad Dressing After Removal Method/Paste Flux? | 6 June, 1998

| | What methods do people use to dress pads after removing and before replacing the BGA? | | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | | Dave F | Dave, | Here's one. Why wick? If you are using eutectic spheres. All you are concerned with is rough coplanarity. Jeez, oxymoron. Sorry. What I'm trying to say is that you don't need to remove the solder. You just need to make it all even. Try this yourself. Use a wide tip on your iron. Drag across the pads. NO WICK. Occasionally, you will have to wipe the tip so you will be removing some solder but the point is to make all the pads roughly similar. Then spread Paste Flux. It's very important that you use paste flux. Talk to your paste sales ass. (yuk yuk) You can place a new BGA on top of this and rework. All will be good. The paste flux cleans the spheres / pads and holds the part in place. There will be sufficient solder still on the pads and in the spheres of the BGA to get a reliable solder joint. It's a heck of a lot faster. As for high temp spheres, you're up the creek and you need to take the time unless someone has a better way. | Cheers, | Justin Justin: When you say "paste flux," do you mean flux in paste form or the flux of my paste? Dave F

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Bob Willis

#15604

Re: BGA Pad Dressing After Removal Method | 7 June, 1998

If any one needs a procedure for rework and repair of BGA there is a document on my Web Site to download www.bobwillis.co.uk | What methods do people use to dress pads after removing and before replacing the BGA? | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | Dave F

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Dave F

#15605

Re: BGA Pad Dressing After Removal Method / Where's The Beef? | 8 June, 1998

| If any one needs a procedure for rework and repair of BGA there is a document on my Web Site to download www.bobwillis.co.uk | | What methods do people use to dress pads after removing and before replacing the BGA? | | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | | Dave F Bob: I followed your suggestion, but found no procedures on reworking BGAs. Are you blatantly using this forum to promote your commercial services? Dave F

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Earl Moon

#15606

Re: BGA Pad Dressing After Removal Method / Where's The Beef? | 9 June, 1998

| | If any one needs a procedure for rework and repair of BGA there is a document on my Web Site to download www.bobwillis.co.uk | | | What methods do people use to dress pads after removing and before replacing the BGA? | | | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | | | Dave F | Bob: I followed your suggestion, but found no procedures on reworking BGAs. Are you blatantly using this forum to promote your commercial services? Dave F Dave, You should be nicer and more thoughtful. After all, Bob is an internationally known consultant offering us all wonderful "free" advice. Besides, don't you think you should take his test posted above. I certainly am. Boogie, The Moonman

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Chris Haynes

#15603

Re: BGA Pad Dressing After Removal Method | 27 June, 1998

| What methods do people use to dress pads after removing and before replacing the BGA? | We use solder wick and a soldering iron, focusing on not "dragging" the wick across vias. This is laborous and booring. Who has a better way? | Dave F SRT makes a automated machine called a Pinnacle Scavenger that does a good job of site dressing. Their phone number is 978-392-0633. Chris Haynes BTW, I do not work at SRT....

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Gary Miller

#15602

Re: BGA Pad Dressing After Removal Method | 7 July, 1998

after you have removed the solder from the pads you can reapply solder psate onto the pads using a single site stencil printer from Mini Micro Stencil.

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