Soldering Electrical Flex Circuits

Objective

To heat multiple joints on flex circuit strips to 180-200°F within seven seconds for a soldering application. 

End Product

flex circuits

Equipment

Ambrell 1 kW power supply, remote heat station with one 1.2 µF capacitor and a specially designed induction coil. 

Materials

Copper bonded to polyester flex circuit strips, Solder Plus Paste 63NC-A, 0.0625” thick Teflon sheets

Temperature

183°F

Frequency

278 kHz

Testing

A specially designed induction coil was used to provide even heat in the area where the fingers of the flex circuits overlap. Initial tests were done to establish a heating pattern and determine time-to-temperature. After a very light coat of the solder paste was applied to the circuit connections, a small amount of pressure was applied to the Teflon sheets to hold the circuits together. RF power was then applied for 6.5 seconds to flow the solder paste and bond the flex circuits

Benefits

Consistent and repeatable results were achieved using the 1kW power supply in 6.5 seconds at 183°F.

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