This paper discusses the heat dissipation mode of this high-precision instrument.As we all know, the environment in space is very harsh, for the environment on Earth. So the effect of temperature change on electronic components is very big. After studying the surface, the structural parts of the electronic equipment above the space, the material requirements are very high, especially the structural parts installed on the PCB board. As guided by the above title, therefore, we focus on the heat dissipation scheme on PCB. Based on the project designed by our engineers, we share a liquid cold plate design scheme.
What is the Invar36,UNS No. K93603 material?
Here we want to introduce a very important metal material, which is InvAR 36 UNS No. K93603. Alloy Invar36 is a 36% Ni-ferro alloy with a thermal expansion rate close to zero in the temperature range -100°C to 200°C, about one-tenth that of carbon steel.It is a very special material, which will not have any deformation to the change of environmental temperature, so as to avoid the failure of some instruments and equipment in space caused by material deformation.When designing this liquid cold plate, our engineers have repeatedly verified and confirmed the processing details with the customer, so that this complex processing cold plate can be used in space to ensure the stable operation of the picture processing calculation of astronomical glasses.
How to heat and process this material?
1,After rough machining preform cleaning and annealing
a. Cleaning by organic solvent to remove surface contamination.
b. Annealing in an inert atmosphere such as hydrogen or at low pressure P<1E-5 TORR.Alternatively heating can be done in salt.Heat to 845° ± 5° C, hold for 1 hr.Cool part at rate of max 80 C/hr to room temperature.
2,After machining preform stress relief and ageing
a. Heat to 315° ± 5°C at max rate of 90° C/hr hold for 1hr.Cool part at rate of max 90° C/hr to room
temperature.
b. Heat to 95° ± 2°, hold for 24 hr, Heat/cool rate max60°C/hr.
3,The manufacturer may preform final machining (nomore than 0.2mm) after heat treatment if required.
4,After final machining part is to be sealed in a bag to prevent corrosion.
Why use the SUS304 stainless steel material for channels?
The bottom material of the liquid cooling plate is determined. What material is used for the flow channel of the whole liquid cooling plate? After repeated trials and tests by our engineers, we finally give up the use of copper C1100, but use SUS304 stainless steel material. The main problem to be considered is whether the deformation of the liquid cooled plate is affected by thermal expansion.
What is the making process of this liquid cold plate?
Engineers buy back the material, according to the customer’s required size, the product processing in the required size range, and then CNC machining, installation of the chip position, uniform arrangement of the channes, machining into a concave shape groove, used to press the stainless steel tube, at the same time filled with epoxy bonding.We also have requirements for epoxy ,the thermal conductivty higher than 1W/(m*k), so that the bottom plate and stainless steel pipe tube tightly fit together. Then bake, here we also pay attention to set the temperature range, do not let the Inva36 material base plate heat treatment failure. After 3 hours, the epoxy set. We began to use CNC machine to process the flatness of the whole product, ensuring that the flatness is less than 0.05 within the area of 100x100mm.
The following is the whole product manufacturing process we share. I hope it will be helpful to your design. If you have any needs, please contact our sales.
