The application of potassium fluoaluminate in the welding of high efficient micro-channel liquid cold plate

A cold plate is a heat exchanger for a single fluid (gas, water, or other cooler).
Because the cold plate has a set of extended surface structure, the cooling channels of smaller equivalent diameters and the geometrical shape of the costal surface which is beneficial to enhance convection heat transfer, the heat transfer coefficient is high.
The heat flux density of air cooled cold plate is smaller, while the heat flux density of the cold plate is larger.
The cold plate can effectively cool the heat dissipation of power components, printing plate assembly parts and electronic cabinet.
Therefore, the application of cold plate in the thermal control of electronic devices has been widely valued.
In the cold plate, there are many microchannels and channel bars, and there are many kinds of different types of diversion blocks, which are larger in the inner cavity of the cold plate.
Considering mechanical properties and thermal conductivity, 6063 can be used to strengthen aluminum alloy.
After double-sided finishing (the thickness of the cavity wall thickness is thin), under certain water pressure to maintain a certain time without leakage and deformation.
Its forming methods using welding, but because of the cold plate cavity internal issued numerous tiny channels, in the welding, ensure seal and connect easily to tiny channels blocked, deformation and other technical problems, so the choice of welding method and research must be conducted.
At present, the commonly used welding methods are mainly divided into three types: fusion welding, brazing and solid welding.
Complex structure of microchannel heat pipes, consider cold plate after welding technical requirements, because the welding is easy to weld around the microchannel, such as jam or melt splashing into the cavity, so this kind of structure is not suitable for using welding welding.
For solid phase welding, such as friction stir welding, the results of the study show that, on the one hand, due to the restriction of the mixing head, the internal diversion block cannot be welded;
On the other hand, the friction stir welding is mainly applied to the joint, which should be selectively adopted for the step joints.
Because of the pressure head (shoulder) diameter greater than the contour refers to the rod (mixing head) in diameter, to ensure that no microchannel, on channel inside will not stir welding area, so as to affect the structure of the cold plate stiffness.
Therefore, solid-phase welding is also difficult to realize the whole welding forming of the microchannel cold plate.
If stir friction welding, the joint design and process should be studied.
At present, the method of aluminum brazing is mainly salt bath aluminum brazing, vacuum aluminum brazing and gas protection Noclock without corrosion-brazing brazing.
For the salt bath aluminum brazing, it is not suitable to use after the salt welding of the inner cavity of the micro-channel is difficult after soldering.
For this purpose, the feasibility study of the brazing of vacuum aluminum brazing and gas protection Noclock without corrosion-brazing was carried out.

The solder used for the brazing of Noclock is potassium fluoaluminate (potassium cryolite), which we have introduced before.