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Heat Sink Clamping Force
Heat sinks are typically used to dissipate heat generated by electronic components such as processors. The clamping force refers to the pressure applied to hold the heat sink firmly in contact with the heat source (e.g., CPU). It is achieved through mechanical means such as screws, clips, or clamps.
The amount of pressure applied when mounting a heat sink onto a processor greatly determines the thermal resistance experienced by the interface. This can greatly affect the performance of the heat sink in transferring heat away from the processor. The efficiency of thermal transfer is critical to the peak performance of high end processors operating at several GHz frequencies. Understanding the behavior of the heat sinks under different clamping forces is crucial to developing and deploying an effective heat sink solution.

The Challenge

Understanding and characterizing the clamping force applied on a processor under a heat sink by tightening of screws holding the two together. 

Graph for heat sink
Image

Finding sub-miniature load cells that can be squeezed in between the base plate and the heat sink and experiments performed to generate a plot of applied clamping force or pressure vs thermal conductivity.

The Solution: Sub-Miniature USB Load Cell kit with SensorVUE software

The Heat Sink Measurement kit is fully calibrated and read-to-use and comes with four sub miniature load cells, one four port USB load cell interface and SensorVUE software. 

You can buy this kit with either the Wika F1222 100 lb load cells or the Loadstar Sensors' RSB5 100 lb load cells to meet your specific needs.

You can connect up to four load cells into the DI-400U USB interface. Each load cell MUST be connected and calibrated with a particular port & MUST be used with that port only.

The DI-400U can be connected to a PC or Tablet running Win 8/10/11 and is powered by the USB port. No external power or USB hub is needed. Use SensorVUE software to capture and display data in real time at up to 40 Hz per channel. 

DI-400U

Four Channel USB Interface

Calibration

Compression

Four Sub-miniature Load Cell Kit with USB Output

Miniature and sub-miniature load cells are the smallest load cells we offer and are used in application that have very small openings and are constrained by available space. Some load cells like the RSB5, REB5 button laod cells can be used to measure compression forces only whereas some such as the REB7 or RES2 miniature S-Beam load cell or the iLoad Mini Capacitive load cells with threaded stud can be used to measure tension or both compression and tension if calibrated in both directions. For this particular application we use either the Wika F1222 load cell or the RSB5 load cell depending on the design of the cavities in the base plate of the assembly.

Four Sub Miniature Load Cells with DI-400U and SensorVUE Software
Kit Includes:


Four Sub-miniature Load Cells
DI-400U Load Cell Interface
SV-1000 SensorVUE Software
Add Calibration
Add Accessories

How to use the USB load cell kit to measure clamping force

A base plate is machined to create small circular cavities to locate and hold the sub miniature load cells in place. These cavities are just about a millimeter in depth to allow for the wiring to come out of the cavity unimpeded. You can make channels to allow the wiring to come out of the base plate. As designed, the nipple of the load cell is supposed to stick outside the cavity. The upper heat sink plate is supposed to come in contact with the nipples of the load cells. As the screws holding the two plates together are tightened, the clamping force goes up and is measured by the load cells.

Heat Sink
The Heat Sink is placed on top of the load cells placed in the cavities inside the base plate
Sub Miniature Sensor carrier plate for heat sink measurement
The sub miniature load cells are placed in the four cavities and the wires carefully routed through the channels.
Heat Sink Clamping Force Measurement Solution
The screws that hold the Heat Sink and the base plate are tightened with a Torque Controlled screw driver. As the screws are tightened, you can see the clamping force go up dramatically. You can see the clamping force as a numerical value or as a Force vs. Time plot as the user tightens the screw and the user can see the values and use it as a feedback to carefully apply the right amount of clamping force. SensorVUE software shows the force data in real-time on your PC or tablet.

The four wires from the load cell are attached to one port each on the DI-400U via an 8 pin terminal block. Each load cell is calibrated with one port and labeled to identify each set as a pair. Each load cell MUST be paired with the port that it was calibrated with and must be used together and cannot be mixed and matched with any other port unless they are calibrated and identified together.  Then the output from the DI-400U can be put into the USB A port of a WIndows 8/10/11 PC or Tablet. SensorVUE software can be used to display, log, plot data in near real time. Data can be saved as a Comma Separated Values (CSV) file and opened in Microsoft Excel or other analysis programs.

Heat Sink Clamping Force Measurement Solution

We offer complete USB Heat Sink Clamping Force Measurement Solution in two configurations - with Wika F1222 load cells or Loadstar Sensors' RSB5 load cells.

Wika F1222 USB Kit:


4 Wika F1222 100 lb. Capacity Load Cells
DI-400U Four-Channel USB Interface
SV-1000 SensorVUE Software
Compression Calibration

Loadstar RSB5 USB Kit:


4 RSB5 100 lb. Capacity Load Cells
DI-400U Four-Channel USB Interface
SV-1000 SensorVUE Software
Compression Calibration

Still have questions about the Clamping Force Measurement solution for Heat Sinks?
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