Dear Technetters, 
we have been seeing increasingly problems with wrinkles in outerlayer copper foil on certain jobs. 
The wrinkles are coming from the press-lamination of multilayers. 

We have tried different things to minimize the problem like optimising heat up and cool down time and temperature, different types of presspads, awareness at lay up, adding copper areas to the underlying layers, different prepregstyles amo. 

If any of you have some additional inputs to the cause of the problems, we will be very interested in hearing from you.

With best regards

Jan Thuesen

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