Gap filler vs gap pad

Gap filler vs gap pad

Gap Filler vs Gap Pad: What Are the Differences?

Materials for heat dissipation have to be used in a large number of applications: New electronic devices and components, for example in the automotive industry or consumer electronics, are becoming smaller and smaller. At the same time, more and more functions are being implemented in the smallest of spaces.

Under the keyword Thermal Management is optimized in this area. Thermally conductive materials can be found in household appliances as well as in standard smartphones and tablets or in LED lighting technology. Other areas of application are engine construction, applications in power electronics or battery systems in hybrid and electric cars.

There is always an attempt to transfer the heat from electrical components to a heat sink or heat sink via improved contacts. dissipate into an assembly that acts as a heat sink.

In order to close larger gaps and thus improve heat dissipation, there are basically two products available: gap fillers and gap pads

What is a gap filler?

Gap fillers are thermally conductive, liquid-applied materials. These thermally conductive gap fillers are often applied by metered mixing of a two-component system using a metering system. Silicone-based, polyurethane-based or acrylate-based systems are often used as a basis. The silicone-free gap filler systems based on polyurethane or acrylic are increasingly being used.

After applying these materials, the gap filler hardens. Once cured, the material forms a strong but compliant interface that conducts heat away from electronic components, resulting in longer life and higher performance.

They are often used as a replacement for thermal pads because they achieve lower thermal impedance and allow more design flexibility. The gap fillers are also well suited for the large-scale production of electronic components such as batteries, inverters/converters, motors and power electronics.

What is a gap pad ?

Gap Pads are soft, elastic, relatively thick mats with heat-conducting properties. Thanks to their material strength and elasticity, gap pads compensate for differences in height between components. Here, too, silicone-based, polyurethane-based or acrylate-based systems are often used as a basis. The silicone-free systems based on polyurethane or acrylic are increasingly being used.

The low level of self-adhesion of the gap pads, which can be achieved through special settings, enables simplified pre-assembly in many cases. Self-adhesive versions of the gap pads can also be used where stronger adhesive forces are required. It is important to ensure that the adhesive fits the system, ie adhesive systems based on silicone, polyurethane or acrylate are used.

In our article Silicone adhesive vs. acrylic adhesive we compare both adhesive systems.

What is the difference between gap fillers and gap pads?

Gap fillers are often applied by mixing a two-component system that is applied to one of the two substrates (eg electronic component). This component is then combined with a heat sink until a certain thickness is reached. The material then forms a firm but conforming interface. It is also possible to fill existing cavities with gap fillers so that no pressure has to be exerted.

Thermal pads, on the other hand, are pre-cut into a desired shape, applied to a substrate, pressed together to the set thickness and fixed.

The applied compressive load forces the firm but resilient pad to make intimate contact with the rough surfaces of the heatsink, PCB or component. In contrast to solid thermal pads, gap fillers flow into the small valleys, seal surface roughness and create closer contact with the surface of the individual components. This allows for more efficient heat transfer between the top and bottom substrates through the use of the gap filler.

Comparing the key characteristics of the two types, the relative cost of using thermal pads is high due to the expensive scrap that results. In contrast to the gap fillers, the gap pads are first produced in the form of mats and then punched or plotted. This inevitably creates more waste. Air pockets are more common in gap pads because they cannot reach the tiny gaps created by the surface roughness.

Gap fillers are the answer to design flexibility as hardness and working time can be adjusted via the mixing ratio of the two parts of the gap filler. And when it comes to applying the product, the large form factor gap pads can be tricky to apply without entrapping air, and automation is difficult. On the other hand, gap fillers are well suited for large-scale production.

However, it must also be considered that there is a cost associated with automating gap filler processing. As a first step, our customers often decide to use pre-assembled gap pads in order to later rely on the automated processing of the gap filler in a large-scale project.

How to increase the cure speed of a gap filler?

In order to increase the cure speed of most gap fillers, potting materials and/or adhesives, the temperature of the part to which the materials are applied must be increased. This can be done with an oven, heat lamp, or induction heating. The parts can be preheated to the desired temperature or the material can be applied first and then the part can be heated.

As a rule of thumb, the curing speed roughly doubles for every 10 degrees Celsius increase in temperature. It should be noted that for rigid materials, increasing the curing speed increases the risk of generating high internal stresses in the material, which can compromise its mechanical strength and its ability to withstand thermal and/or mechanical shock.

In principle, we recommend that you proceed very carefully when determining the temperature profile, as damage to the electronic components can also occur in addition to damage to the actual gap filler materials.

What thermal conductivities can be achieved with gap fillers or gap pads?

The gap fillers available from Gap Filler have thermal conductivities of up to 7 W/mK at different Shore hardness levels. The gappads come with a thermal conductivity of up to 17 W/mK.

Silicone-free and silicone-containing gap fillers and gap pads

The standard delivery program includes silicone-free gap fillers and gap pads as well as silicone-containing gap fillers and gap pads. There are a number of selection criteria to determine which solution is most appropriate.

Datasheets Gap Filler and Gap Pad Datasheet

The data sheets for the materials are available from us. If you need a data sheet, we will be happy to send you a link to obtain the data sheet

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