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Rework units with parylene coating

Peter

#34724

Rework units with parylene coating | 3 June, 2005

I am working on an application requiring removing BGAs from a board coated with parylene.

These BGAs have low standoff with less than 0.015" after SMT soldering. Can some comment on a reliable and consistent process to perform such rework? given that the coating has penetrated under the BGA and provide additonal bonding to the pcb hence preventing the device to be pulled.

Rgds, Peter

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#34730

Rework units with parylene coating | 3 June, 2005

We've never tried to remove Paraylene from a BGA, but we stayed [in seperate rooms] at the Red Roof Inn.

Parylene/Paraxylyene is a great coating and can be selectively removed by several methods. IPC-7711 (Rework of Electronic Assemblies) has a section devoted to removing the five generic types of conformal coating. * According to that document the best method is to use thermal energy (overcuring the parylene and removing by abrasion - usually with a dental-style drill or similar item). * The next best method is to use a grinding / scraping method (again, dental tool, minor surgery scalpel, rotary brush, etc). * Micro blasting comes in last. Micro blasting can be an efficient method to remove coating, but to our knowledge (sales claims aside) no one has yet perfected a way to use micro blasting without developing significant static charges.

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jimby

#34820

Rework units with parylene coating | 8 June, 2005

You will have to machine the part off down to the top of the balls. Wick solder off from individual sites one at a time. All that will be left is Parylene shell where balls once were. Take an orangestick and alcohol to break up and remove. Tricky part will be finding machining parameters that will not cause damage to boards

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#34827

Rework units with parylene coating | 8 June, 2005

Microshot blasting suppliers that recognize steps must be taken to control potentail dmage from ESD are: * Comco 2151 North Lincoln Street Burbank, CA 91504-3344; 800-796-6626 818-841-5500 F818-955-8365 info@COMCOinc.com http://www.comcoinc.com * CCR Co; 3815 South Main St, Santa Ana, CA 92707; 800-443-2726 F 714-513-1510 info@CCRCo.com http://www.ccrco.com

* Crystal Mark [613 Justin Ave, Glendale, CA 91201-2396; 818-240-7520 F818-247-3574 http://www.crystalmarkinc.com sales@crystalmarkinc.com

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#34909

Rework units with parylene coating | 13 June, 2005

Peter:

Based on our company's experience with removing a variety of different coatings, including parylene, the BGA's can be removed.

We would use a chemical etch followed by a neutralizing process. We would then reflow the devices and pry them off.

Each of the parts and components that need to be "saved" need to have their data sheets checked for compatability with the process and temperatures. ESD and handling care must also be taken.

Contact me offline if you need further help...

Bob Wettermann BEST Inc bwet@solder.net

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