As chip speeds skyrocket and system sizes diminish, designers and manufacturers face new and complex challenges.
To help them address these challenges and ensure that products meet performance and reliability requirements, IPC released the A revision of IPC-4204 ‘Flexible Metal-Clad Dielectrics for Use in Fabrication of Flexible Printed Circuitry’. The updated standard now details materials that let designers and manufacturers move to far higher frequencies.
“We need to know that each material will still work at high frequencies, that there will not be any crosstalk or any other problems,” said Clark Webster, an application engineer at All Flex LLC and chair of the IPC flexible circuits base materials subcommittee that worked on the revision.
Along with enabling the reach of higher frequencies, the revised standard focuses on improved dimensional stability, particularly for adhesiveless assemblies. Enhanced dimensional stability is very important in environments like cellphones, where flex circuits must match up with traces on glass that can be smaller than 12 microns, Webster noted.
“In the past, designers knew the dimensional stability and the shrinkage and other factors that impacted stability, and they could modify the artwork to meet changing parameters,” Webster explained. “It is a lot easier to meet today’s requirements if you have better stability and do not have to guess how much the material will change during processing.”
IPC-4204A addresses the basic aspects of flexible circuit board design and also includes more focused information. Specification sheets at the end of the document provide users with information for classes of materials, including polyimides, liquid crystal polymers and polyesters. “Within these families of materials, people can see the requirements, parameters and test methodologies. Specification sheets make it easy for people to see the best material for their applications,” said Webster.
Now that IPC-4204A is available to industry, committee members are moving on to tackle another flex technology, revising IPC-4203 ‘Adhesive Coated Dielectric Films for Use as Cover Sheets for Flexible Printed Circuitry and Flexible Adhesive Bonding Films’. IPC-4203 is often used by flex manufacturers in conjunction with IPC-4204A. IPC-4203A is expected to be released later this year.
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