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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Youngho Song

#13306

Relationship between BGA and PCB substrate | 10 December, 1998

Hi everybody? I heard that typical FR-4 would not acceptable for BGA application. What is the main reason? (thermal property? or CTE?) Sombody please answer me the requirement of PCB substrate for PCB application. Thanks.

Youngho Song

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Earl Moon

#13307

Re: Relationship between BGA and PCB substrate | 10 December, 1998

| Hi everybody? | I heard that typical FR-4 would not acceptable for BGA application. | What is the main reason? | (thermal property? or CTE?) | Sombody please answer me the requirement of PCB substrate for PCB application. | Thanks. | | Youngho Song | Plastic BGA expansion rate and thermal properties relatively match FR-4's TCE, or most other resin/glass (epoxy, modified epoxy, polyimide, BT) type PCB substrates. Most PCB types indicated have an X-Y axis TCE of about 14 ppm/degree C. with copper at about 18 ppm. There is little problem in this area.

Ceramic BGA's had past problems without an effective compliant interface to which balls are attached. You know ceramic's TCE to be between 5-7 ppm - not closely matching resin/glass, unconstrained/tailored PCB's. Early CBGA's used an acrylic/Kapton interface that often failed. The latest versions have proven much more reliable and are used routinely with glass supported, resin type substrates.

Earl Moon

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