In the ___________ type of mounting the SCR is pressed between two heat sinks.

Question

Examoogle · Accepted Answer

Press-pak mounting

Explanation: Press-pak mounting, also known as hockey-puck mounting, involves sandwiching the SCR between two high-thermal-conductivity heat sinks. This design provides double-sided cooling, significantly increasing the power handling capacity of the semiconductor device.

Working Principle: The SCR wafer is held under high pressure between two metallic heat sinks using a clamping mechanism. This structure minimizes the thermal resistance between the junction and the cooling medium from both sides. Proper contact pressure is essential to ensure low electrical resistance and efficient heat dissipation.

Key Formulas: $R_{	heta JA} = R_{	heta JC} + R_{	heta CS} + R_{	heta SA}$ — Total thermal resistance formula for heat dissipation

Key Points: Press-pak mounting provides superior heat dissipation compared to stud-mounting due to dual-sided cooling.; The thermal expansion match between the silicon wafer and the mounting structure is critical in press-pak devices.; Used extensively in high-current industrial applications where efficiency and thermal stability are paramount.

Advantages: Excellent double-sided cooling capability; High current rating capacity; Lower thermal resistance ($R_{	heta}$)

Disadvantages: Requires specialized, precise clamping hardware; More complex assembly compared to bolt-down types; Requires maintenance of constant contact pressure

Applications: High-voltage DC (HVDC) transmission; Large industrial motor drives; Traction power converters

Additional Info: Stud-mounting (Option B) is commonly used for lower power SCRs where the stud acts as both a terminal and a heat sink connection.. Bolt-down mounting typically refers to devices with a flat base that is mechanically bolted to a heat sink, primarily single-sided.

Answer: C is correct — Press-pak mounting uses two heat sinks to sandwich the SCR for efficient double-sided cooling.

Exam Tip: Always relate thermal resistance to the physical contact area and pressure; higher clamping pressure in press-pak reduces thermal resistance, allowing higher junction current ratings.

Related Questions

Discussion (0)