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Material Witness: R.I.P. Speedboard C

• The GenClad 280 material has a slightly higher dielectric constant, which means that it may not be a perfect "drop-in" for the Speedboard C material, and it is possible that small adjustments in board design elements that depend critically on dielectric constant may have to be made. But since every board design is different, and the use of the bonding material will differ percentage wise, this would have been the case anyway.
• The GenClad 280 material has a lower Tg, which in principle means a higher overall Z-direction movement. However the GenClad material is ceramic filled, which mitigates the movement, and has a relatively low tensile modulus (0.67*10^6 psi) because the resin system consists of both thermoset and thermoplastic domains, so that it will more readily absorb small differences in Z-direction movement. Because this material will only be a small percentage of the volume or thickness of the final composite, the overall effect is will be minimal.

On the other side, GenClad 280 has some definite advantages:

• It uses standard FR-4 processes and does not require high temperatures to develop its Tg or to bond to PTFE or other higher-temperature materials.
• It has a lower water absorption (0.04% vs. 0.1%).
• Its high thermal decomposition temperature (>420°C) has been shown to provide resistance to high-temperature processing and fabrication, and assures the ability to be processed through multiple cycles in sequential processing.
• Low dielectric loss means that the product will impact overall design loss budgets less than Speedboard C, which may be important especially in layers in which transmission lines abut the bond layer.
• It has a better shelf-life (one year at room temperature) and better handling characteristics (not tacky or dusty) for easier PCB manufacturability.

Every design has its own unique set of requirements, and nobody can predict with certainty that any one product will fully take the place of the venerable Speedboard C, but OEM and board shop results to date indicate that the GenClad 280 product is a good candidate to work over a wide range of applications with good results.

Try it. We think you'll like it.

Chet Guiles is a consultant for Arlon Electronic Materials.

About Arlon Arlon Electronic Materials Division, now part of Rogers Corporation (www.rogerscorp.com), is a major manufacturer of specialty high performance laminate and prepreg materials for use in a wide variety of printed circuit board (PCB) applications and in several distinctive markets. www.arlon-med.com

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