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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Paste-in_hole and CTE

Gary

#3450

Paste-in_hole and CTE | 26 July, 2000

I have been following forum discussions here and eslewhere, attended technical sessions at APEX and have been experimenting with the paste-in-hole process on some of our new product. I have run into one problem I have never seen mentioned, that is a CTE missmatch causing the board to warp along the length of connectors. The available lists of "Acceptable" materials do not seem to address this. Any insight that may help my research would be appreciated.

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#3451

Re: Paste-in_hole and CTE | 27 July, 2000

Gary: That's curious. Tell us more about your process steps, temperature profiles, paste, warping of the board without the PIH processing, components, etc

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Gary Simbulan

#3452

Re: Paste-in_hole and CTE | 28 July, 2000

Belive it or not, these boards were run through a Centech batch mode Vapor Phase machine. Single stage top side IR preheat. Vapor temp 218 C. Solder paste is an SN62 RMA.The boards were FR4 8 layer w/ solder mask, fairly conventional as might be expected since we are an aerospace OEM. The connector was a 3 inch long pin single row pin stripin a 5.2 inch long board for interconnecting stacking boards. The boards did not warp when run without the connector. The boards come out of the oven just below liquidus. As they cooled, the boards warped up as the connector expansion must have been greater than the board. There was no damage due to heat evident to the connector. This leads me to the conclusion that not all temperature compatible connector materials are compatible with the process.

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