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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


TCP solder / desolder / rework

Wolfgang Hantz

#15557

TCP solder / desolder / rework | 5 June, 1998

We offer an upgrade service for notebooks with 486 SX/DX CPUs up to 586-133 MHz using the AMD 5x86-133 MHz CPU in the PQFP package. We are pretty succesful with this service and until today we did more than 1000 notebook upgrades this way. Now, - the next generation of CPU Upgrades for notebooks will be more difficult. The Intel Pentium CPUs used in notebooks are in a higher desity TCP package, that requires higher skills and better tools. Unfortunally, Intels Web-Site doesn�t name any manufacturer for the necessary tools. Who could help me with Know-How, tools, materail a.s.o. ? Thank you ! HANTZ + PARTNER GMBH Wolfgang Hantz hantz@compuserv.com www.upgrade.de

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Wolfgang Hantz

#15559

Re: TCP solder / desolder / rework | 9 June, 1998

| We offer an upgrade service for notebooks with 486 SX/DX CPUs up to 586-133 MHz using the AMD 5x86-133 MHz CPU in the PQFP package. We are pretty succesful with this service and until today we did more than 1000 notebook upgrades this way. | Now, - the next generation of CPU Upgrades for notebooks will be more difficult. The Intel Pentium CPUs used in notebooks are in a higher desity TCP package, that requires higher skills and better tools. | Unfortunally, Intels Web-Site doesn�t name any manufacturer for the necessary tools. | Who could help me with Know-How, tools, materail a.s.o. ? | Thank you ! | HANTZ + PARTNER GMBH | Wolfgang Hantz | hantz@compuserv.com | www.upgrade.de Wolfgang, Reworking TCP's. A blast from my past! I was the process engineer on a TCP line at TI when Intel introduced it. We had placed over 70,000 TAB/TCP sites prior to the Pentium's introduction, so we got pretty good at it. We got pretty good at rework on those first 10,000, too. Here's the deal. It sounds like you won't be needing to salvage the old chip, since you're in the upgrade business, so that makes it a lot easier. Some companies market machines to remove/replace TCP's, and claim that you'll be able to re-use the chip, but those machines don't really work worth a hoot, and they're very expensive. To get good rework, you'll need: - Stereo microscope - Good controlled soldering irons (like Metcal) - Highly skilled, patient operators - Tweezers All rework needs to be done under the scope. The package is so small (leads are <0.1 mm wide) that it's impossible with just a magnifying light. Ring lights on the scope work best, because the gooseneck lamps get in the way and require constant readjustment. As for the soldering irons, my operators didn't like the small, micro-tips. They preferred regular Metcals & regular tips. Some liked bigger tips than others. It depends on what they're comfortable with. The operators are the key. I couldn't believe what some of these ladies could pull off! Highly skilled is an understatement. I think anyone who's been doing rework on fine-pitch full-time for at least five years would be able to fit your bill. To remove a part, touch the top of the lead's foot with the hot iron and gently lift with the tweezer. It doesn't take long to heat up; there was only about 500 microinches of solder under there to begin with. Don't touch the iron to the keeper bar, though; you'll reflow the adhesive there and detach the bar. Then you've got 300 leads running in different directions. Depending on the die attach material used, you should be able to loosen the die attach with heat. Solvents will clean up the adhesive left on the board. If you don't have to reuse a component, you can remove the leads without heat. Just grab a corner with a tweezer and pull. The leads will pop off like you're unzipping a zipper. To redress the pads, (this is kind of like BGA where you add the solder before the heat cycle), use your iron and solder wire. Just run it down the pads. This is a pretty easy step to get used to for skilled operators. Some of them like using the banana tip for this one. To put a part back down, place it in the general vicinity, line it up as best as possible, and tack the corner leads. Go from one corner to the opposite corner, then back to the other two. Once your four corners are tacked, then you can just run that iron across the rest to achieve reflow. Just don't keep it hot for too long. There's not a lot of solder there, and if you turn it to intermetallic, you'll have a bear of a time trying to remove the part later if you have to. Look for heel fillets. As in SMT, they are the most important. Don't lose sleep over toe fillets. Peel test data indicates they're not worth the risk of overheating stuff. Don't try to test your joint by poking on the leg of the lead. You can bust an inner bond trying this (been there; done that). Use a low solids, high-temperature liquid flux. Alcohol based is better for this application. Ask your vendor for mechanical samples of the TCP's to practice on. Mechanical samples are just electrical test failures. Treat your rework operators well. Keep them happy. Hire a massage therapist to come in and rub their shoulders. Buy them lunch once a week. Take them out for happy hour. Give them a lot of breaks. Staring through a scope for eight hours a day is not fun. I would last about one hour before going bonkers, so I have a great deal of respect for these folks. They are artists, not operators. One more thing - the room needs to be clean. Not Class 10 or anything, but relatively dust and fiber free. Sticky mats at the doors keep dust down. Selection of office furniture and smocks keep fibers down.

Now I have a question for you. How do you plan on excising/forming the leads of the device when you receive the Tape Carrier Package? This really isn't as scary as it seems. It is an aquired skill, however, and you'renot gonna find it from a temp agency at eight dollars and hour. Good luck! Chrys

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Chrys

#15560

Re: Nice philosophy | 10 June, 1998

| | We offer an upgrade service for notebooks with 486 SX/DX CPUs up to 586-133 MHz using the AMD 5x86-133 MHz CPU in the PQFP package. We are pretty succesful with this service and until today we did more than 1000 notebook upgrades this way. | | Now, - the next generation of CPU Upgrades for notebooks will be more difficult. The Intel Pentium CPUs used in notebooks are in a higher desity TCP package, that requires higher skills and better tools. | | Unfortunally, Intels Web-Site doesn�t name any manufacturer for the necessary tools. | | Who could help me with Know-How, tools, materail a.s.o. ? | | Thank you ! | | HANTZ + PARTNER GMBH | | Wolfgang Hantz | | hantz@compuserv.com | | www.upgrade.de | Wolfgang, | Reworking TCP's. A blast from my past! I was the process engineer on a TCP line at TI when Intel introduced it. We had placed over 70,000 TAB/TCP sites prior to the Pentium's introduction, so we got pretty good at it. We got pretty good at rework on those first 10,000, too. | Here's the deal. It sounds like you won't be needing to salvage the old chip, since you're in the upgrade business, so that makes it a lot easier. Some companies market machines to remove/replace TCP's, and claim that you'll be able to re-use the chip, but those machines don't really work worth a hoot, and they're very expensive. | To get good rework, you'll need: | - Stereo microscope | - Good controlled soldering irons (like Metcal) | - Highly skilled, patient operators | - Tweezers | All rework needs to be done under the scope. The package is so small (leads are <0.1 mm wide) that it's impossible with just a magnifying light. Ring lights on the scope work best, because the gooseneck lamps get in the way and require constant readjustment. | As for the soldering irons, my operators didn't like the small, micro-tips. They preferred regular Metcals & regular tips. Some liked bigger tips than others. It depends on what they're comfortable with. | The operators are the key. I couldn't believe what some of these ladies could pull off! Highly skilled is an understatement. I think anyone who's been doing rework on fine-pitch full-time for at least five years would be able to fit your bill. | To remove a part, touch the top of the lead's foot with the hot iron and gently lift with the tweezer. It doesn't take long to heat up; there was only about 500 microinches of solder under there to begin with. Don't touch the iron to the keeper bar, though; you'll reflow the adhesive there and detach the bar. Then you've got 300 leads running in different directions. | Depending on the die attach material used, you should be able to loosen the die attach with heat. Solvents will clean up the adhesive left on the board. | If you don't have to reuse a component, you can remove the leads without heat. Just grab a corner with a tweezer and pull. The leads will pop off like you're unzipping a zipper. | To redress the pads, (this is kind of like BGA where you add the solder before the heat cycle), use your iron and solder wire. Just run it down the pads. This is a pretty easy step to get used to for skilled operators. Some of them like using the banana tip for this one. | To put a part back down, place it in the general vicinity, line it up as best as possible, and tack the corner leads. Go from one corner to the opposite corner, then back to the other two. Once your four corners are tacked, then you can just run that iron across the rest to achieve reflow. Just don't keep it hot for too long. There's not a lot of solder there, and if you turn it to intermetallic, you'll have a bear of a time trying to remove the part later if you have to. | Look for heel fillets. As in SMT, they are the most important. Don't lose sleep over toe fillets. Peel test data indicates they're not worth the risk of overheating stuff. Don't try to test your joint by poking on the leg of the lead. You can bust an inner bond trying this (been there; done that). | Use a low solids, high-temperature liquid flux. Alcohol based is better for this application. | Ask your vendor for mechanical samples of the TCP's to practice on. Mechanical samples are just electrical test failures. | Treat your rework operators well. Keep them happy. Hire a massage therapist to come in and rub their shoulders. Buy them lunch once a week. Take them out for happy hour. Give them a lot of breaks. Staring through a scope for eight hours a day is not fun. I would last about one hour before going bonkers, so I have a great deal of respect for these folks. They are artists, not operators. | One more thing - the room needs to be clean. Not Class 10 or anything, but relatively dust and fiber free. Sticky mats at the doors keep dust down. Selection of office furniture and smocks keep fibers down. | | Now I have a question for you. How do you plan on excising/forming the leads of the device when you receive the Tape Carrier Package? | This really isn't as scary as it seems. It is an aquired skill, however, and you'renot gonna find it from a temp agency at eight dollars and hour. | Good luck! | Chrys Chrys, Kudos for your view on the treatment of your operators. That is truly one of the most pertinent criteria for being a good manager in this industry. I focused a NEPCON paper on it. People tend to overlook the operators yet they're the ones who can make or break you. Again, my hat comes off to ya!! Best Regards, Justin Medernach

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Mike Moninger

#15558

Re: TCP solder / desolder / rework | 18 June, 1998

| We offer an upgrade service for notebooks with 486 SX/DX CPUs up to 586-133 MHz using the AMD 5x86-133 MHz CPU in the PQFP package. We are pretty succesful with this service and until today we did more than 1000 notebook upgrades this way. | Now, - the next generation of CPU Upgrades for notebooks will be more difficult. The Intel Pentium CPUs used in notebooks are in a higher desity TCP package, that requires higher skills and better tools. | Unfortunally, Intels Web-Site doesn�t name any manufacturer for the necessary tools. | Who could help me with Know-How, tools, materail a.s.o. ? | Thank you ! | HANTZ + PARTNER GMBH | Wolfgang Hantz | hantz@compuserv.com | www.upgrade.de

Chrys just about said it all -But- Intel recommends a thermally conductive goo that goes between the bottom of the chip and the substrate, the stuff that's commonly used is a silver filled thermally and electrically conductive compound that must be kept frozen and is really hard to apply on an occasional basis, without the wonderful machines. Try Chomerics p/n 66-10-0075-t705 or the like, its a thermally conductive putty-like substance that comes in a roll. One roll will last forever in your application. Per Intel, it does not have to be electrically conductive. Also, we have had some success with the hot air pencil rather than the direct iron approach. Depends on operator preference. Excise and form is a problem for low volumes. I can give you recommendation for high quality tooling vendor if you like. I don't know of a cheap way out, as the parts are EXTREMELY delicate. All the comments on operator skill levels and TLC needs certainly apply in this field of endeavour. Regards, Mike

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