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Ask the Experts

December 22, 2008 - Updated
December 21, 2008 - Originally Posted

Procedure for Baking Flexible Circuits

What is the proper procedure for baking flexible circuits where we need to bake the flex at 125 C for 6 hours? Does the oven need to be preheated before we begin this process?

M. K.

Expert Panel Responses

This is a very good question and most people have different views but I am an old flexible printed circuit board guy both polyester and kapton material sets. The idea is to drive water absorption out of materials and it should a slow process of allowing the pcb to ramp to temperature and cool to ambient or close to it over 8 to 12 hours and the temperature should be 105 degrees C. Naturally Kapton material sets can handle higher temperatures than polyester. KAPTON can handle 125 degrees C but the idea is to drive water out of the material set slowly and effectively.

Mark McMeen
VP Engineering Services, STI Electronics Inc.

Mark T. McMeen is STI Electronics Inc.ʼs Vice President of Engineering Services. He oversees the daily operations of the Engineering Services division of STI. He has over 18 years experience in the manufacturing and engineering of PCBs.

What's the end users process? Soldering the flex (lead free or not), Surface finishing, plasma processing, drying a high layer count rigid flex preventing shorts at electrical? Typical Bake for soldering flex circuits and rigid flex 12 layer and below: 2 hours min @ 250 degrees F Solder within 2-3 hours after bake. No need for 6 hours if the fabricated has laminated at the correct temp and time. Yes oven should be convection with air flow and at temperature.

James Mahoney
Applications Project Manager, Quick Turn Flex Circuits LLC

James Mahoney is a Technical Operations Manager with a 20 year track record in managing new product introduction. He is a skilled leader, motivator and problem solver with a strong background in Product Knowledge and Engineering Management.

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