4.2 Ring style cold plate (cont’d)4.2.2 Clamp locationThe cold plate is clamped onto the solder mask covered traces on the board at a minimum of 5 mm from the package (the shadow of the package). The package shall be centered +/- 10% of the distance from the package shadow to the clamp. The cold plate clamp area must be a minimum of 4 mm wide. The test board design must have the vias for hand soldered jumper wires close enough to the edge of the board that the vias will not interfere with clamping of the cold plate. Clamping force should be evenly applied and be sufficient that the board will not move with respect to the ring if a 200 gram force is applied to the board. The measurement results are not sensitive to clamping force. Thermal grease does not have to be used.4.2.3 Example designsExamples of the ring cold plate design are included as figures A1 and A2 in annex A.4.3 Insulation requirementsThe package opening in the top and bottom of the cold plate are insulated. The insulation material with a conductivity less than 0.1 W/m•K is faced with a low emissivity aluminized plastic film. There should be a 1 to 5 mm air gap between the package and the insulation and between the bottom of the test board and the insulation on the bottom of the fixture. If solder mask over the traces on the board do not provide sufficient electrical insulation, tape not exceeding 0.075 mm in thickness may be used to electrically insulate the board traces such that the package can be tested. 1 to 5 mm Gap Insulation to Board or Insulation to Package Board Temperature Thermocouple te with tape essary5 mm MinimumFigure 1 — Illustration of the ring style cold plate RJB test fixture in cross section