Types of Heat Sink Attachments

Versal ACAP Packaging and Pinouts Architecture Manual (AM013)

Document ID
AM013
Release Date
2020-07-16
Revision
1.0 English

There are six main methods for heat sink attachment. The following table lists their advantages and disadvantages.

  • Thermal tape
  • Thermally conductive adhesive or glue
  • Wire form Z-clips
  • Plastic clip-ons
  • Threaded stand-offs (PEMs) and compression springs
  • Push-pins and compression springs
Table 1. Heat Sink Attachment Methods
Attachment Method Advantages Disadvantages
Thermal tape
  • Generally it is easy to attach and is inexpensive
  • Lowest cost approach for aluminum heat sink attachment
  • No additional space required on the PCB
  • The surfaces of the heat sink and the chip must be very clean to allow the tape to bond correctly
  • Because of the small contact area, the tape might not provide sufficient bond strength
  • Tape is a moderate to low thermal conductor that could affect the thermal performance
Thermally conductive adhesive or glue
  • Outstanding mechanical adhesion
  • Somewhat inexpensive, costs a little more than tape
  • No additional space required on the PCB
  • Adhesive application process is challenging and it is difficult to control the amount of adhesive to use.
  • Difficult to rework
  • Because of the small contact area, the adhesive might not provide sufficient bond strength
Wire form Z-clips
  • It provides a strong and secure mechanical attachment. In environments that require shock and vibration testing, this type of strong mechanical attachment is necessary.
  • Easy to apply and remove. Does not cause the semiconductors to be destroyed (epoxy and occasionally tape can destroy the device).
  • It applies a preload onto the thermal interface material (TIM). Preloads actually improve thermal performance.
  • Requires additional space on the PCB for anchor locations
Plastic clip-ons
  • Suitable for designs where space on the PCB is limited
  • Easy to rework by allowing heat sinks to be easily removed and reapplied without damaging the PCB board
  • Can provide a strong enough mechanical attachment to pass shock and vibration test
  • Needs a keep out area around the silicon devices to use the clip
  • Caution is required when installing or removing clip-ons because localized stress can damage the solder balls or chip substrate
Threaded stand-offs (PEMs) and compression springs
  • Provides stable attachments to heat source and transfers load to the PCB, backing plate, or chassis
  • Suitable for high mass heat sinks
  • Allows for tight control over mounting force and load placed on chip and solder balls
  • Holes are required in the PCB taking valuable space that can be used for trace lines
  • Tends to be expensive, especially because holes need to be drilled or predrilled onto the PCB board to use stand-offs
Push-pins and compression springs
  • Provides a stable attachment to a heat source and transfers load to the PCB
  • Allows for tight control over mounting force and load placed on chip and solder balls
  • Requires additional space on the PCB for push-pin locations