Transtector Announces "Super Cell" Diodes

Transtector Systems announced that an extensive two-year development and testing program has successfully resulted in the development of a higher performance silicon suppressor component for use in their surge protective devices. Transtector’s research and development engineers worked closely with designers at component suppliers around the world to create a new process for making silicon avalanche suppressor diodes (SASDs) for Transtector’s products.

Transtector uses these SASDs as key components to dissipate the extra energy generated by transient overvoltages before they can damage equipment. To meet projected demand, Transtector has qualified five suppliers from inside and outside the U. S. who are approved to manufacture these new “super cell” diodes. By changing the way the SASD components are made.

Transtector Systems is able to improve the amount of surge energy their products handle, reduce the physical size of some products and increase the products’ reliability. Transtector products using these super cells are tested in-house against 8x20 and 10x1000 microsecond waveforms at several stages throughout the manufacturing process to verify current sharing and maximum performance. These tests involve state of the art generators capable of producing up to 30KV and 30KA.

The improvements to the diode manufacturing process and how they impact a surge protective device are outlined more specifically below.

Die Uniformity to Produce Evenly-Matched Diodes
A double-diffusion process refines the structure of the dies used to cast super cell diodes, producing more uniformity from die to die. This uniformity allows the cells’ current handling capability to be matched within a two-percent variation when arranged in arrays for transient voltage suppression. Because a surge current is evenly distributed across closely matched components, the super cell improves the overall performance of the product. It is difficult to match off-the-shelf components to this degree because they can vary as much as 20 percent.

Special Cell Header Material
Super cell diodes have a special cell header material that improves heat-sinking capabilities. This material improves performance and increases the components’ longevity by dissipating heat faster and more efficiently during high current surge events or repetitive operation.

Refined Cell Header Attachment
Gold flashing, nickel metalization and vacuum solder techniques create voidless attachment of the conductive header to the super cell diode. This refined attachment reduces overheating and cell fracture problems common to off-the-shelf transient voltage suppression diodes. Voids often trap moisture, contaminants and excessive heat, causing premature breakdown of a surge protective device.

Improved Lead Attachment
The high performance super cell diodes are connected in arrays using custom, surface-mount lead attachment processes, providing full coverage of the cell header with minimal lead inductance. Under surge conditions, the current will be evenly distributed across the entire surface of the super cell, keeping the voltage protection level as low as possible. Conventional lead attachment uses the “nail head” method where a small, straight lead is attached to a cell diode using a tab only slightly larger than the lead. This method concentrates the surge current in one small area of the cell, an area that could be its weakest point. The small straight lead also adds considerable inductance to the cell, causing the voltage protection level to rise significantly above what the cell could provide. Stacked super cell diodes using these custom leads, as in Transtector’s APEX Series of panel protectors, allow for customization of protection levels for use in areas of highly unregulated power.