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Parylene Coated BGA Rework

Lake

#24097

Parylene Coated BGA Rework | 10 April, 2003

Does anyone have any experience with parylene coated BGA's. Can they be masked so parylene doesn't get underneath? How do you remove and replace? Is machining them off the only viable option? If so are there any special requirements /special fixturing anyone is using?

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Lake

#24098

Parylene Coated BGA Rework | 10 April, 2003

Does anyone have any experience with parylene coated BGA's. Can they be masked so parylene doesn't get underneath? How do you remove and replace? Is machining them off the only viable option? If so are there any special requirements /special fixturing anyone is using?

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#24104

Parylene Coated BGA Rework | 10 April, 2003

Q1: Can they be masked so parylene doesn't get underneath? A1: Your parylene applyer may be able to mask area, but in general no. This stuff is cured in a vacuum chamber to make sure that it gets into every past corner.

Q2: How do you remove and replace? A2: Belt sander, sand blasting, grinding wheel, etc.

Q3: Is machining them off the only viable option? A3: Yes, this stuff is very tough.

Q4: If so are there any special requirements /special fixturing anyone is using? A4: Assemblies that require repair are hacked and have limited usefulness.

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#24122

Parylene Coated BGA Rework | 12 April, 2003

... continuing with

Q2: How do you remove and replace? A2: Belt sander, sand blasting, grinding wheel, etc.

Parylene/Paraxylyene is a great coating and can be selectively removed by several methods. The IPC-7711 (Rework of Electronic Assemblies) has a section devoted to removing the five generic types of conformal coating. According to that document: * Thermal energy (overcuring the parylene and removing by abrasion - usually with a dental tool or similar item) is the best method. * Grinding / scraping method (again, dental tool, minor surgery scalpel, rotary brush, etc.) is the next best method. * 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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