Importance of Improving Thick Film Adhesion of Aluminum Nitride Ceramic Substrate
High-power components are integrated using the original power thick film hybrid integrated circuit technology because of its excellent thermochemical stability, high thermal conductivity, non-toxicity, corrosion resistance, and high temperature resistance. However, because aluminum nitride is easily hydrolyzed and absorbs moisture in the environment, it may also react with water slowly at ambient temperature to be hydrolyzed and enter into the nitride. The water vapor in aluminum is hard to bake and get rid of, so thick films printed and sintered on aluminum nitride ceramic substrates don't stick well and aren't consistent or uniform.
On the other hand, the reliability of power thick film hybrid integrated circuits is somewhat impacted by the poor adhesion of the thick film printed and sintered on the aluminum nitride ceramic substrate, as well as the poor adhesion between the aluminum nitride ceramic substrate and the tube base, which affects the efficiency of heat transfer and, in extreme cases, results in the substrate falling off. In order to enable complete volatilization of the water vapor absorbed by the aluminum nitride ceramic substrate, a method to improve thick film adhesion of aluminum nitride substrate is presented in this article. This approach also enhances the adhesion between the substrate and the tube base.
Methods for Improving Thick Film Adhesion of Aluminum Nitride Ceramic Substrate
This method is based on the theory of aluminum nitride moisture absorption. Following are the fundamental procedures.
Heating to Bake
The aluminum nitride ceramic substrate is heated and baked in a high vacuum atmosphere, and the water vapor is totally volatilized and evacuated using a simultaneous heating and vacuuming technique. The vacuum degree of the high vacuum environment is over 1.0 x 104 Pa; the vacuum coating equipment's built-in heating mechanism is used for heating and baking, with a temperature range of 200°C to 400°C.
Forming Metal Thin Film
Magnetron sputtering or electron beam evaporation is used in magnetron sputtering vacuum coating equipment or electron beam evaporation vacuum coating equipment, respectively, to deposit a thin layer of material onto the front of an aluminum nitride ceramic substrate under a very high vacuum. On the front of the aluminum nitride ceramic substrate, a layer of high-temperature-resistant and high-melting-point composite metal film is created, and on the rear, a similar layer is integrally formed. The high vacuum environment has a vacuum level more than 1.0 x 104 Pa, and the composite metal film used to withstand the extreme heat is a multilayer film with a melting point greater than 1000 degrees Celsius.
Screen printing, Sintering and Resistance Adjusting
Screen printing, sintering, and resistance adjusting of the thick film conduction band and the thick film stop band are carried out on the front side of the aluminum nitride ceramic substrate that has sputtered or evaporated the composite metal film. Additionally, the conventional hybrid integration is carried out, and the resulting substrate and the tube base are produced. They are much better attached to one another.
Advantages of This Method for Improving Thick Film Adhesion
(1) The surface metal sheet and the aluminum nitride ceramic substrate are in close proximity and adhere strongly;
(2) High-reliability bonding between the bonding wire and the metal layer on the aluminum nitride ceramic substrate;
(3) A strong bond is made between the aluminum nitride ceramic base and the bottom of the tube;
(4) Increase the effectiveness of heat transmission between ceramic substrates, tube bases, and high-power chips;
(5) Enhance the dependability of power thick film hybrid integrated circuits.
Conclusion
This article discusses a method for improving thick film adhesion of aluminum nitride ceramic substrate, which pertains to the technological area of film creation of aluminum nitride ceramic substrates. The products that are made using this method find widespread application in a variety of industries, including aerospace and aviation, shipbuilding, electronics and communications, medical equipment, and industrial control, amongst others. They are particularly useful in the field of high-reliability equipment systems, and they have expansive market prospects and application space.