How to Design with Thermal Pad vs. Paste in Your Circuit Board
Using thermal pads vs paste is an important decision when deciding how to best attach a heat sink to a power-hungry component like a CPU. Each of these materials gives the important benefit of heat transfer and reduced temperature, but there are other points to be considered when using a heat sink with a thermal pad or thermal paste. Assembly houses also need to know which option a design will use, requiring clear documentation be provided from design data.
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Do you remember the first time you opened an old computer and saw a bulky metal heat sink on a CPU? Heat sinks and other cooling methods won’t go away anytime soon, and it’s often up to the board designer to determine whether a heat sink will be needed to remove heat from critical components. There are some simple strategies you can use to ensure your board will remain cool and that components will not get too hot during operation.
When working with heat sinks in a new design, engineers need to determine how they will attach a heat sink to the device. This often needs to happen in conjunction with an assembler, who will try to automate the process to ensure the heat sink is securely attached to its host component. Thermal pads and thermal paste are the two primary methods for attaching a heat sink to a hot component, giving a secure fixture with high thermal conductivity and heat transfer into the heat sink.
Thermal pads and thermal paste are two methods for securely mounting heat sinks to integrated circuits, particularly to CPUs, GPUs, FPGAs, and other components with high power consumption. Some points to consider when selecting thermal pads vs. thermal paste include:
- Assembly: Which of these two materials can your assembler’s processes support?
- Replacement: Will the end user ever need to replace the heat sink?
- Durability: How long will the product be deployed in the field and under what conditions?
- Cost: How will each option affect per-board materials and assembly costs?
- Shape: Does the heat sink have an odd shape, and does the shape match that of a typical thermal pad?
Each type of material has its own advantages in different areas. Thermal paste can be messy and difficult to remove if the heat sink is ever replaced, making thermal pads a better option. However, thermal paste can be deposited in almost any shape, it costs less, and is much more durable. The table below shows a summary of the advantages of each type of material for mounting heat sinks.
Ease of assembly
Ease of replacement