Anode bonding is a method of wafer bonding widely used in the microelectronics industry that uses a combination of heat and static electric fields to seal two surfaces together. This bonding technique is most commonly used to seal glass layers onto silicon wafers. Also known as field-assisted bonding or electrostatic sealing, it is similar to direct bonding and unlike most other bonding techniques, it usually does not require an intermediate layer, but differs in that it relies on electrostatic attraction between surfaces to apply a high voltage to the component as ions move.

Metal can be bonded to the glass using anode bonding and silicon can be bonded to the silicon using a thin intermediate layer of the glass. However, it is particularly suitable for silicon glass bonding. Glass needs to have a high content of alkali metals (such as sodium) in order to provide mobile positive ions. A specific type of glass is usually used, which contains about 3.5% sodium oxide (Na 2 O).

During bonding, the surfaces of the two components are smoothed and thoroughly cleaned to ensure a close contact between them. They are then sandwiched between two electrodes, heated to 752-932℃(400-500℃Fahrenheit), and an electric potential of several hundred to thousands of volts is applied so that the negative electrode, which is called the cathode, is in contact with the glass, and the positive electrode (anode) is in contact with the silicon. The positively charged sodium ions in the glass become mobile and move toward the cathode, leaving a small positive charge near the boundary with the silicon wafer, which is then held in place by electrostatic attraction. The negatively charged oxygen from the ions of the glass migrates towards the anode and reacts with the silicon upon reaching the boundary to form silicon dioxide (SiO 2). The resulting chemical bond seals the two components together.

This technology is used to encapsulate sensitive electronic components to protect them from damage, contamination, moisture and oxidation or other adverse chemical reactions. Anode bonding is particularly relevant to the micro electromechanical systems (MEMS) industry, where anode bonding is used to protect devices such as microsensors. The main advantage of anode bonding is that it can produce strong and long-lasting bonds without the need for adhesives or excessive temperatures, which are needed to fuse components together. The main disadvantage of anode bonding is that the range of materials that can be bonded is limited, and there are other limitations to the combination of materials because they need to have similar coefficient of thermal expansion rate - that is, they need to expand at a similar rate when heated, otherwise differential expansion can cause strain and warping.

Internationally common anode bonding high-voltage power supplies are as follows: