Authored By:
Dean Hattula, John Coonrod
Rogers Corporation, Advanced Circuit Materials Division
Summary
With the ever accelerating demands in printed circuit board (PCB) design, the choices of advanced laminate materials have become fewer and fewer. The trends continue towards higher frequency requirements, exotic via structures, shrinking hole to hole pitch, multiple lamination cycles, increased operating temperature, and more stringent environmental regulations for halogen-free and lead-free solder assembly! These constantly evolving new challenges for the PCB industry have made many of the tried and true materials obsolete. Demands for high speed digital (HSD), high density interconnect (HDI), halogen free, lead-free processable materials are becoming more prevalent and the laminate technology supporting these demands is still in the early stages and in so me cases does not yet exist.
Conclusions
In summary, there are few halogen free flame retardant laminates available and for those on the market currently, they are not considered mid loss and thermally stable. Theta circuit materials appear to be unique where they meet both these criteria along with other necessary requirements for good PCB fabrication and reliability. The difficulty is comparing materials to this unique material fairly. The appropriate comparisons were done here with materials that have a long proven record in the PCB industry and as a group these comparison materials have the attributes to verify thermal stability and mid loss performance.
Through multiple lead-free solder reflows, 288°C solder floats, eyebrow crack testing and other demanding high reliability tests not addressed in this paper, such as HATS, CAF, IST, liquid-to-liquid and moisture conditioning, it was found that this newly developed halogen free material is very thermally stable. The electrical properties were found to be very good as well. The claim of a mid-loss material was verified from insertion loss testing compared to well-known low loss and high loss materials. Also, material dispersion of the dielectric constant was found to be very good and consistent over frequency which can enable a much more stable eye diagram for high speed digital applications.
Initially Published in the IPC Proceedings
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