Design007 Magazine


Issue link:

Contents of this Issue


Page 31 of 111

32 DESIGN007 MAGAZINE I FEBRUARY 2022 ere are numerous prepreg choices in the PCB industry. In the past, the choice of pre- preg was oen dominated by PCB fabrication concerns. e prepregs used for high frequency or high-speed digital (HSD) address many of the same PCB fabrication concerns, but they also have other properties which are important for consistent high-frequency or HSD perfor- mance. ere are also other bonding materi- als used as prepreg, such as a film or non-glass woven bonding materials, which are called bonding film or bondplys. Basically, these pre- pregs and other bonding materials are used to adhere the different layers in a multilayer PCB and can have a significant influence on many aspects of the circuit. Over the past several years there have been more high-volume PCB programs that are using millimeter-wave (mmWave) frequen- cies. Most of these applications, until the past few years, are PCBs typically built as a four- or six-layer circuit with only the top two cop- per layers being related to the high frequency circuitry. Many of the more recent mmWave PCBs, especially those used in high resolution automotive radar, are multilayer PCBs with many high frequency circuit layers and in some cases the entire multilayer PCB is designed to have all layers to be supportive of mmWave fre- quencies. It is these types of circuitry where the prepreg and bondplys can be critical to good RF performance and still need to maintain all the other properties for good PCB fabrication and reliability. A circuit using mmWave frequencies is a propagating medium for the wave, and the wavelengths at these high frequencies are very small. Generally, the small wavelength means the propagating wave will be more sensitive to anomalies in the medium than a propagating wave at a lower frequency. ere are several items which are relatively normal to the circuit fabrication process, which could be consid- ered an anomaly. Having a very small etching Selecting Prepreg for Millimeter-wave PCB Applications Lightning Speed Laminates by John Coonrod, ROGERS CORPORATION

Articles in this issue

Archives of this issue

view archives of Design007 Magazine - Design007-Feb2022