Attachment Method - Clip Selection Select the package to attach and check the type of clip(s) to be used, then press the search button.
Package Type All Clips   Ball Grid Array (BGA) Microprocessor Surface Mount Plastic Power Packages (TO-220, TO-218, etc.) Clip Type Flat Form Composite Molded Wire Form Integrated

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Part Number Package Type Anchor Point Clip Type

The use of clips for providing the contact pressure is a widely accepted method to attach heat sinks with electronic components. Clip mounting techniques provides a number of advantages: Clips provide a more uniform pressure over the mating surface. Although screw mounting achieves higher pressures, the force applied by screws may be centered at one end of the package often resulting in a loss of coplanarity between package (e.g. TO-220, TO-247) and the heat sink. Clips provides a constant interfacial pressure between the package and the heat sink enhancing thermal conductivity. This is a mandatory requirement when phase change thermal interface materials are used. Clips are faster to apply than aligning and tightening screws. The clips snap into slots on the heat sink, package, or PCB to hold the device in place and/or for PC board insertion. Clips regulate the force applied and ensure that the same force is applied to each package/heat sink pair. Hence there is no danger of over-tightening (deforming the package and/or heat sink) or under-tightening (increasing the contact thermal resistance). Clips prevent chip breakage caused by mismatches in the CTE (coefficient of thermal expansion) differences. Clips allow removal and/or separation of the heat sink and/or device if needed. Clips replace torqued hardware in assembling transistors to heat sinks.

Clip Types A variety of clip types are available depending on the application. The following examples show the way designers typically use clips. These ideas by no mean encompass all available solutions and do not prescribe the only ways in which the clips can be used.

Saddle Clips Saddle clips can be anchored directly to the heat sink, package and the PCB. When using saddle clip type solutions, the heat sink (or PCB) materials are thin in cross-section, typically less than 5mm in thickness. The clips push into holes cut into heatsink (or PCB) material and lock against the back face of the heat sink (or PCB). These clips produce contact forces in the range 20-60 N.

U Clips This clip type clamps the device and the heat sink material together. Variations on this clip type allow devices to be clamped to the front and back of the heat sink block using the same clip. 'U' clips typically impart forces in the 20N-40N range. This force is partly dependent of the thickness of the heat sink material, i.e. thicker the material, the greater the force.

Extrusion Mounted Clips This clip solution has the clip anchored in a feature in the extruded heat sink. The figure below shows one solution type / approach, where the clip fits into a shaped slot in the heat sink material. This solution can produce contact forces in the range 15 - 25 N.

Wire Form Clips Wire form clips are an inexpensive way to produce irregularly shaped attachment springs. They exhibit the same force control properties as all other types of springs. They are used in three different ways: The can be used to lay across the center of a heat sink and be anchored to a socket or the PCB. The advantage of these clips is that less fin space is required in order to accommodate the clip. Special retention holders can hold the spring in place on the heat sink. They can be inserted and anchored directly into the Printed Circuit Board. The ends of these wireforms are designed in such a manner to prevent damage to the PCB. In addition, these clips can also be designed to create an electrical conduction path from the heatsink to a ground plane in the PCB. Contact our engineering staff on the specifics to accomplish this design function. The clips can be hooked into a couple of anchors previously soldered into the PCB. Instead of anchoring into the PCB, the wire form anchors into the eyelets. The benefit to this design is that the integrity of the PCB is not challenged and the stress is transferred off of the component.

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