FAQ

Frequently Asked Questions

Common Questions About Our Products

What thermal conductivity test method was used to achieve the values given on the data sheet?
A test fixture is utilised that meets the specifications outlined in ASTM D5470
Currently, Gap Pad VO, Gap Pad VO Soft and Gap Pad VO Ultra Soft are offered with or without an adhesive on the Sil-Pad 800/900 carrier-side of the material. The remaining surface has natural inherent tack. All other Gap Pads have inherent tack.
Depending on the surface being applied to, if care is taken, the pad may be repositioned. Special care should be taken when removing the pad from aluminum or anodised surfaces to avoid tearing or delamination.
The characteristic of the rubber itself has a natural inherent tack, without the addition of an adhesive. As with adhesive-backed products, the surfaces with natural tack may help in the assembly process to temporarily hold the pad in place while the application is being assembled. Unlike adhesive-backed products, inherent tack does not have a thermal penalty since rubber itself has the tack. Tack strength varies from one Gap Pad product to the next.
Again, depending on the material that the pad is applied to, in most cases they are repositionable. Care should be taken when removing the pad from aluminum or anodised surfaces as to avoid tearing or delaminating the pad. The side with natural tack is always easier to reposition than an adhesive side.
Depending on the application and the pad being used, Gap Pad has been reworked in the past. Bergquist has customers that are currently using the same pad for reassembling their applications after burn-in processes and after fieldwork repairs. However, this is left up to the design engineer’s judgment as to whether or not the Gap Pad will withstand reuse.
From -60°C to 200°C, there is no significant variance in hardness for silicone Gap Pads and Gap Fillers.
Shelf life for Gap Pad is one (1) year after date of manufacture. For Gap Pad with adhesive, the shelf live is (6) six months after the date of manufacture. After these dates, inherent tack and adhesive properties should be recharacterised.
The test method used is the Bellcore Extraction method #TR-NWT-000930; refer to Bergquist Application Note #56.
Gap Pad VO materials and Gap Pad A3000 are more stable at elevated temperatures. Gap Pad in general can be exposed to temporary processing temperatures of 250°C for five minutes and 300°C for one minute.
Yes, all Gap Pad materials are electrically isolating. However, keep in mind that Gap Pad is designed to FILL gaps and is not recommended for applications where high mounting pressure is exerted on the Gap Pad.
Refer to the Pressure vs. Deflection chart in Bergquist Application Note #116.

Gap Pad and Gap Filler can be used wherever air can be replaced, such as between a heat-generating device and a heat sink, heat spreader or housing. This can be done using one sheet of Gap Pad or individual pieces of appropriate thicknesses, or by using Gap Filler if stack-up tolerances and height variations are significant.

The better a Gap Pad complies and conforms to a rough or stepped surface, the less interfacial resistance will be present due to air voids and air gaps. This leads to a lower overall thermal resistance of the pad between the two interfaces.
1) Silicon Gap pad and Gap Fillers, like all soft silicone materials, can extract silicone fluid (refer to Bergquist Application Note #56). Also note that Gap Pad and Gap Filler have some of the lowest extraction values for silicone-based gap filling products on the market and if your application requires no silicone, see our line of Sil-Free material. 2) Primarily for aerospace applications, outgassing data is detailed in Bergquist Application Note #117, tested per ASTM E595
A reinforcement carrier is generally utilized in Bergquist Gap Pads for ease of handling. When testing hardness, the reinforcement carrier can alter the test results and incorrectly depict thinner materials as being harder. To eliminate this error, a 250mil rubber puck is molded with no reinforcement carrier. The puck is then tested for hardness. The Shore hardness is recorded after a 30 second delay.
The simple answer is: it does not! To make a true and useful cost comparison, one should compare the cost of FR4 + heat sink + device mounting hardware (such as clip, screw or clamp) + interface (Sil-Pad) plus the cost of manual assembly versus the Thermal Clad automated surface mount assembly. Taking into consideration all relevant costs, Thermal Clad system is lower overall when comparing it to a traditional printed circuit board (PCB) and heat sink assembly.

Again the costs have to be like for like. Unlike Thermal Clad, Direct Bonded Copper (DBC) always involves some method of mechanically attaching it to a heat sink. This is either a solder operation or a mechanical frame to secure the DBC. It is not possible to secure the DBC with fixing holes built into the delicate ceramic whereas Thermal Clad can support fixing holes, rivets, pressed studs etc. In simple terms: Thermal Clad can be worked like any metal sheet, even forming into a box-shape is possible. Taking into consideration all relevant costs, Thermal Clad system provides lower overall costs when comparing it to a DBC substrate and heat sink assembly.

Yes, you can! Even if your company does not have the capability to assembly Thermal Clad, it is still possible to take advantage of Thermal Clad’s high thermal performance and also remove the need for a number of clips and screws per power device. Thermal Clad can be used to solder all of your power devices in a row and create a sub-assembly. The device leads are formed, then “through hole” mounted into your control PCB. Bergquist can offer names of sub-contract manufacturing assembly houses to build these assemblies. We call this system: Thermal Clad-Power Rail.
This depends on your application. For example in thermally demanding applications you will be concerned about transferring as much heat to the heat sink as possible. By assuming intermat contact between Thermal Clad and the heat sink you create the best possible heat path. Bergquist have a material designed to interface Thermal Clad to heat sinks called Hi-Flow 225FAC which is applied as a pad. It softens to a paste like consistency and wets the surfaces when it reaches a threshold temperature. In addition to this Thermal Clad can be formed with a bias so the part ends up convex. When bolted down with fixing holes around the edge, the part is assured intermat contact.
There is a need for both. Depending on your application, either copper or aluminium can be the best choice, since they both have their own specific advantages. Aluminium is a good choice for cost and thermal properties. But if your application demands heavy copper weight traces or tracks due to large currents or for mounting ceramic devices, then, as the copper thickness approaches 10% of the thickness of aluminium, the base material should be changed to copper. The use of a copper base for Thermal Clad is especially suitable when using naked devices or ceramic chip capacitors. Copper is closer to these components in thermal co-efficient of expansion which makes for more reliable solder joints. If you carefully select a thinner copper base versus the thicker aluminium base then the costs can be similar.
Any type of finish that can be applied to regular FR4 can be applied to Thermal Clad as well. This traditionally ranges from Hot Air Solder Levelling (HASL) for the reflow process and nickel-gold for Al wire bonding as an example. A solder mask is often used to keep parts clean and help with pattern recognition, it also contains the moulten solder during the re-flow process.
This is not required. In most cases if you design the solder pad area to mirror the exposed copper area of the back side of the device, the surface tension created in the molten solder during the re-flow process will bring badly aligned parts into the correct position.

You simply contact us. Bergquist can take care of all of your prototype needs. Obviously we can supply them ourselves, but we also have a network of local printed circuit shops familiar with processing Thermal Clad. They can supply prototypes on our behalf or you can work directly with them.
All you need to get started is:

  • Circuit pattern layout (preferably in electronic format i.e. Gerber)
  • Mechanical design giving:
  • positions for fixing holes and their size
  • overall dimensions and
  • importantly a dimension linking the artwork traces to a mechanical feature.
    (i.e. dimensions of fidusial to datum edges)
  • The material specification
  • The required finish will complete the information we need
The basic sizes ar: 609 x 457mm (24 x 18 inches) or 482 x 406mm (19 x 16 inches). Each panel has a border of 3.2mm (0.125 inches) which should be kept clear of active electrical tracks / traces. The border around the outside of the panel is normally used for tooling holes during the circuit processing of the material.
There is no simple answer to this one as each customer design will be different. As a general rule if your volumes are going to go above 5000 pieces then you might want to consider a punch tool. If the part has an irregular shape then punching or routing is normally used. If you design a rectangular part (i.e. no radii) then v-scoring offers good material utilisation.
A constant-pressure fastener is preferred when using TIC for high performance applications.The constant pressure from a clip or spring washer will ensure adequate pressure is being applied with varying bond line thickness.
Screenprinting the TIC is a fast, low-cost method that delivers a consistent and accurate amount of material on each application. Alternate methods include stenciling, pin transfer and needle dispensing.
All the TIC materials were specifically designed to resist pump-out of the interface, even after many hours of thermal and power cycling.
Yes. Please review our Terms & Conditions before purchasing, as they outline pricing, payments, refunds, and other important sale-related policies.