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

Printed Circuit Board Assembly & PCB Design Forum

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Shrinkage in paper phenolic pcbs


Shrinkage in paper phenolic pcbs | 22 August, 2002

Are having problems with cheap paper phenolic pcbs that appear to have shrunk. That is they no longer match the stencil (stencil is correct). Some people seem to think this is normal, is there an industry standard out there that says what is reasonable to expect from this type of product?

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Shrinkage in paper phenolic pcbs | 23 August, 2002

Ah, CHEAP boards. You pay me now, you pay me later, eh? The buyers get BIG bonuses. The production types get trashed, 'cause they can run aboard they've been doing for years. Wassup?

For a specification, look to: * IPC-6011 - Generic Performance Specification For Printed Boards * IPC-6012A w A#1 - Qualification & Performance For Rigid Printed Boards

� but if you didn�t call-out 6011 & 6012 in your procurement documents, it�s kind of moot. Many fabricators are up-front with their tolerances and tell their customers what to expect. Many of these are posted on the web.

Without drilling into the specifics of your case, 6012 allows considerable reduction in conductor spacing on rigid boards.

What is normal is debatable. What is acceptable should be defined in your procurement documents. Sometimes industry documents represent the sellers� interests in deference to the buyers� needs. Or they make trade-offs between difference requirements. So, sometimes buyers need to take these documents a starting point in describing their requirements.

You may also consider that the balance between the cost of more expensive boards out-weigh the cost of a nice used dispenser. Oooo, new toy!!!

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Shrinkage in paper phenolic pcbs | 23 August, 2002

Here's the bet.

I'll bet the size [ie, length, width, thickness, etc] of the boards remain the same. It's the size of the copper features on the board that is changing.

Right? Right?

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