BANNOCKBURN, IL – Printed circuit boards that incorporate high-speed chips and microwave circuitry have many parameters that are different from more mainstream rigid and flexible printed boards, says IPC. These differences are covered in the “B” revision of IPC-6018, Qualification and Performance Specification for High Frequency (Microwave) Printed Boards.

The revised document provides specific criteria for the allowance of resin smear. In addition, references to embedded passive resistors and capacitors have been included.

“This version also better defines hole breakout requirements that occur when holes aren’t drilled in the center of a pad,” says Michael Luke, chair of the IPC-D22 High Speed/High Frequency Board Performance Subcommittee that developed IPC-6018B.

Thermal stress criteria have also been revised to address advances in the convection reflow process for thermal stressing of microsections or production printed board samples.

“Now we have three techniques for subjecting product to thermal stress for evaluation and acceptance. In the past, there was only one. We’ve also added two new reflow profiles,” says Luke.

The specification also expands the types of finishes that can be used. The B revision includes new requirements for procurement selection, copper wrap/cap plating of filled holes, laminate cracks and voids and etchback.

At the end of the document, a table for inspection criteria has been updated, and an appendix for the space and avionics industries has been added.

For more information, visit www.ipc.org/6018.