Induction sealing glass to encloseย resistors with high frequency induction heating system
Objective Provide a hermetic seal of glass enclosed resistor to a lead
Material Resistorย Kovar rings, 0.1 inch (0.254cm) diameterย Glass tube slightly larger than 0.1 inch (0.254cm) diameter,ย 0.5 (1.27) inch length
Metal lead
Temperature 900 ยบF (482) ยบC
Frequency 324 kHz
Equipment โข DW-UHF-6kW-III induction heating system, equipped with aย remote workhead containing two (2) 1.5 ฮผF capacitors (forย a total of 0.75 ฮผF).
โข An induction heating coil designed and developedย specifically for this application.
Process A three turn concentrator plate coil is used to heat the Kovarย ring for 500 milliseconds. This causes the glass to melt andย seal one side of the resistor. The resistor is then turned over
and the process is repeated to seal the other side using aย second Kovar ring.
Results/Benefits Induction heating provides precise, consistent heat to veryย small parts resulting in repeatable, quality seals.
By heating with medium frequency, arcing (which occurs atย high frequencies) is avoided.