PCB circuit board bonding is a method of wire bonding in the chip production process. It is generally used to connect the internal circuits of the chip with gold or aluminum wires to the packaging pins or gold-plated copper foil on the circuit board before packaging. Ultrasonic waves (usually 40-140KHz) from the ultrasonic generator are transmitted to the chopper through the transducer to generate high-frequency vibration. When the chopper comes into contact with the leads and the workpiece, under the action of pressure and vibration, the metal surfaces to be welded rub against each other, the oxide film is destroyed, and plastic deformation occurs, causing the two pure metal surfaces to tightly contact each other, achieving atomic distance bonding, and finally forming a strong mechanical connection. Generally, after bonding (i.e. connecting the circuit and pins), the chip is encapsulated with black glue.

Key points of bonding processing technology: When cleaning the PCB circuit board, wipe the oil, dust, and oxide layer on the bonding position with a skin, and then clean the wiping position with a brush or blow it off with an air gun. When applying adhesive, the amount of adhesive drops should be moderate, and the number of adhesive points should be evenly distributed at all four corners. It is strictly prohibited for the adhesive to contaminate the solder pads. When pasting (fixing) chips, a vacuum suction pen is used, and the suction nozzle must be flat to avoid scratching the surface of the chip. Check the direction of the chip and ensure that it is adhered to the PCB in a "smooth and upright" manner. The chip should be parallel to the PCB and tightly attached without any virtual space. The chip and PCB should not easily fall off during the entire process. The reserved position between the chip and PCB should be aligned and not deviated. Pay attention to the fact that the direction of the chip should not be reversed. When bonding, the bonded PCB passes the bonding tensile test, with 1.0 wire greater than or equal to 3.5G and 1.25 wire greater than or equal to 4.5G. When bonding standard aluminum wire with a melting point, the wire tail is greater than or equal to 0.3 times the wire diameter and less than or equal to 1.5 times the wire diameter, and the shape of the aluminum wire solder joint is elliptical. The length of the solder joint is greater than or equal to 1.5 times the wire diameter and less than or equal to 5.0 times the wire diameter. The width of the solder joint is greater than or equal to 1.2 times the wire diameter and less than or equal to 3.0 times the wire diameter. During the bonding process, handle with care and ensure accurate alignment. Operators should use a microscope to observe the bonding process for any defects such as broken bonding, wire coiling, misalignment, cold and hot welding, or aluminum peeling. If any are found, relevant technical personnel must be notified to resolve them in a timely manner. Before formal production, there must be a dedicated person conducting an initial inspection to check for any defects such as bonding errors, missing bonding, etc. During the production process, a dedicated person must regularly (with a maximum interval of 2 hours) verify its correctness. Before installing the plastic ring on the chip, it is necessary to check the regularity of the plastic ring to ensure that its center is square and there is no obvious distortion. During installation, ensure that the bottom of the plastic ring is closely attached to the surface of the chip, and there is no obstruction to the photosensitive area at the center of the chip. When dispensing, the black glue should completely cover the PCB sun ring and the aluminum wire of the bonded chip, without any exposed wires. The black glue should not seal the PCB sun ring, and any leakage should be promptly wiped off. The black glue should not penetrate the chip through the plastic ring. During the dispensing process, the needle tip or swab should not touch the surface of the chip inside the plastic ring or the bonded wire. Strict control of drying temperature: preheating temperature is 120 ± 5 degrees Celsius, and the time is 1.5-3.0 minutes; The drying temperature is 140 ± 5 degrees Celsius and the time is 40-60 minutes. After drying, the surface of the black glue should not have any air holes or uncured appearance, and the height of the black glue should not be higher than the plastic ring. Testing generally adopts a combination of multiple testing methods, including manual visual inspection, automatic welding line quality inspection by bonding machine, automatic optical image analysis (AOI) X-ray analysis, and inspection of the quality of inner layer solder joints.