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10 PCB007 MAGAZINE I JUNE 2025 Through-glass Vias in Glass Substrates is month's theme is vias and how best to ensure via quality and reliability. I don't have much expertise in this process area or much to contribute that most of you don't already know. However, I've recently become periph- erally involved in a via technology that may be of more than academic interest to some of us. It entails putting vias in a material not usually associated with PCB manufacturing: through- glass vias (TGVs) in glass substrates. Using glass as a PCB substrate has been bouncing around for a long time, and interest has grown over the past 10 years. Glass has sev- eral advantages over fiberglass/organic resin panels typically used as substrates. Besides having excellent dielectric properties, glass has better dimensional stability over a wider range of environmental conditions, allowing an extremely tight layer-to-layer interconnect overlay. Glass also has greater tolerance for higher temperatures, so glass substrate PCBs can operate reliably over a wider range of tem- perature differences. ere are several other advantages to glass in the design rules for power delivery, but with the higher dimen- sional stability and heat tolerance, the inter- connect density possible with glass increases by an astounding 10 times. One doesn't need a lot of imagination to realize that this means a lot more capability for our electronic devices in the same space. Prototype devices of dou- ble-sided through-hole glass substrate PCBs The Chemical Connection Feature Column by Don Ball, CHEMCUT