What Should You Watch Out for When Using Thermal Conductive Pads? -

Improper use of thermal conductive pads can have devastating effects on your electrical parts – from overheating and reduced equipment reliability to premature component failure. Whether it is choosing the wrong pad, poor installation or inadequate maintenance, they will reduce heat transfer efficiency.

In this article, we will explore some of the most common mistakes to avoid for maximum thermal performance,

Table of Contents

Choosing the Wrong Thermal Pad

The most frequent and expensive error in thermal management is the selection of the wrong thermal pad.

The thermal conductivity rating is not in the correct order: The thermal conductivity of a thermal pad is usually from 1 W/m·K to 15 W/m·K or above. In high power applications, using a lower conductivity pad can retain heat and decrease cooling efficiency.
Poor thickness selection, resulting in poor contact: Pads that are too thick can lead to an increase in thermal resistance, and too thin can mean that the gaps are not covered. Typical industry practice is to achieve a compression of 10% to 30% for maximum contact.
Low quality or incompatible materials: Inferior pads may lose strength, elasticity or fail when subjected to temperature cycling. Check compatibility with operating temperatures which are typically -40°C to 200°C depending on the application.

Improper Surface Preparation

Thermal conductive pads can have a significant effect on the effectiveness of the surface preparation, as the surface may not be adequately prepared. This results in less heat transfer or overheating.

Failure to remove dust or residues: Any dust or residue of old adhesive layers can contribute to higher thermal resistance. This can cause a loss of heat transfer of 10-20% for even thin residue layers. You should always clean surfaces using isopropyl alcohol (≥90%).
Failing to provide flat and smooth contact surfaces: Uneven or warped surfaces form air gaps that are thermal insulators. When contact is achieved, near full coverage with a minimum of voids, the proper contact is obtained.
Reusing old down pads with reduced energy: Over time, thermal pads become less energy conductive and less elastic. Reused pads can not compress as effectively, which can decrease the effectiveness and raise the risk of overheating.

Incorrect Installation Techniques

Even with the proper material, the thermal performance of thermal pads can be significantly affected by improper installation methods.

Partial pad to component alignment: If the pad does not completely cover the heat generating component, heat transfer will not be even. This can cause the formation of hot spots and limit cooling efficiency. Ideally, 100 percent coverage of the contact area should be provided when properly aligned.
Air gaps due to uneven placement: Air has very low thermal conductivity (~0.026 W/m·K), so any trapped air drastically increases thermal resistance. Pads should be applied in even layers to ensure even surface contact and maximum compression.
Unnecessary use of multiple stacked pads: When multiple pads are stacked, their arrangement creates more thermal resistance and lowers the heat transfer efficiency. Rather, employ a single pad that is of the proper thickness, usually 10-30% compression, to ensure optimal thermal performance.

Applying Incorrect Pressure

One of the most common errors in installing thermal pads is the application of the wrong pressure, which directly affects the performance and reliability of thermal pads.

Excessive compression which causes pad deformation or damage: When the thermal pad is compressed too much, it may be beyond the optimum compression range, usually from 10% to 30%, which will cause an uneven compression and harm the sensitive parts. This can cause the material to become fatigued over time and have a lower conductivity.
Too little pressure: Not enough pressure causes the pad to not conform to the irregularities of the surface, creating air gaps and adding thermal resistance. This can lead to reduction in heat transfer efficiency and can lead to the overheating of components.
Failure to secure heat sinks: Improperly attached or unevenly-distributed heat sinks result in uneven pressure distribution across the pad. Proper mounting techniques and the use of mounting tools such as torque-controlled screws provide uniformity of contact pressure and maximum thermal performance.

Ignoring Operating Environment

Thermal conductive pads can lose their performance and durability if they are not used in the proper operating environment, particularly in harsh industrial or outdoor settings.

Thermal pads are usually rated from -40℃ to 150℃ (standard) or 200℃ (high performance). Exceeding these limits can lead to hardening, melting or loss of elasticity that diminishes thermal conductivity.
Moisture, dust or vibration that impacts on performance: These can cause moisture to seep into the pad surface or to be trapped on the surface in the form of dust. Vibration causes the pad to shift over time, leading to air gaps and poor contact efficiency. Before installation, unused pads and small electronic components should be kept clean and separated; labeled plastic storage bins can help organize these parts and reduce unnecessary exposure to dust in production areas.
Industrial environments: Some environments call for special pads (e.g., flame retardant, oil absorbent, electrically insulating). Under extreme conditions, standard pad can fails prematurely and give an unreliable system.

Overlooking Compatibility Issues

In the long run, these incompatibilities can cause loss in performance, degradation of materials, or damage to electronic components.

Chemical incompatibility with parts: Certain thermal pads can be incompatible with plastics, coatings, or metals, particularly at elevated temperatures. This can lead to discoloration, corrosion or dissolution of material. Never assume compatibility with substrates like copper, aluminum, and PCB coatings.
Electrical insulation requirements not considered: Most thermal pads are electrically insulating, but some are not. If it is not confirmed, it may result in short circuits or safety hazards, especially in densely packed electronic assemblies.
Where thermal paste would be more suitable: Thermal pads are suitable for filling gaps, but for very flat high performance interfaces (e.g., CPU), thermal paste provides lower thermal resistance. An incorrect interface material can decrease cooling performance by as much as 50%.

Neglecting Maintenance and Inspection

If thermal management systems are not maintained and inspected regularly, they can slowly lose their effectiveness and become prone to system failure.

Failure to inspect pad condition over time: Thermal pads may deteriorate after 1-3 years depending on operating conditions from thermal cycling. If not checked regularly, decreased elasticity and conductivity could go undetected.
Failure to take notice of overheating or degradation: If the symptoms include temperature rise, discoloration or hardened pads, those are signs of decreased device performance. An increase of only 5–10°C from baseline temperatures can indicate thermal interface failure.
Worn out pads lose contact: Old or compressed pads cannot maintain proper contact. It is recommended that pads be changed at major maintenance cycles or when components are reassembled in accordance with industry best practice.

FAQs

What are thermal conductive pads and how do they work?

These are solid materials made from a mixture of polymer base and conductive ceramic or metallic fillers. They are primarily designed to bridge the gap that exists between the electronic components (that generate heat) and the heat sink.

By replacing air that can act as an insulator for thermal conductivity, they facilitate heat transfer.

When should you replace thermal pads?

You should replace thermal pads when they are cracked or become brittle and cracked. Additionally, when there is thermal throttling, widening “hotspot delta” or increasing system operating temperature.

What causes thermal pad oil leaking?

Usually, the silicone fluid bleeds due to sustained pressure or heat.

Can I use thermal pad and thermal paste in the same system?

No, it is not recommended.

Gallop Innotek: Your Trusted Thermal Pad Manufacturer in China

Whether you are looking for standard or custom thermal interface materials, our engineers will recommend the ideal solution based on application, material type and thermal conductivity.