1. Introduction to Underfill Adhesive Underfill adhesive is a single-component epoxy resin potting material with high fluidity and high purity. It can fill the bottom of CSP and BGA chips through innovative capillary action. After heating and curing, it forms a solid filling layer, which reduces the stress impact caused by the difference in thermal expansion coefficients between the chip and the substrate, improves the structural strength and reliability of components, and enhances the drop resistance between BGA-mounted chips and PCBA.
ASIASEAL underfill adhesive has good fluidity at room temperature, with small filling gaps and fast filling speed. It can cure quickly at a relatively low heating temperature, is compatible with most lead-free and tin-free solders, allows rework operations, and has excellent electrical and mechanical properties.
2. Principle and Application of Underfill Adhesive The application principle of underfill adhesive is to use capillary action to make the adhesive quickly flow through the bottom of BGA chips. The minimum space for its capillary flow is 10μm. This also meets the minimum electrical performance requirements between the pad and the solder ball in the welding process, because the adhesive will not flow through gaps smaller than 4μm, thus ensuring the electrical safety of the welding process.
3. Functions of Underfill Adhesive With portable electronic products such as mobile phones and computers becoming increasingly thinner, smaller, and more high-performance, IC packaging is also becoming more miniaturized and highly integrated. CSP/BGA has been rapidly popularized and applied, and the requirements for CSP/BGA packaging processes are getting higher and higher. The role of underfill adhesive is also increasingly valued.
BGA and CSP are fixed on the circuit board through tiny solder balls. If affected by external forces such as impact and bending, the welding parts are prone to fracture. The underfill adhesive is characterized by rapid flow and rapid curing. It can quickly penetrate into the bottom of BGA and CSP, with excellent filling performance. After curing, it can alleviate temperature shock, absorb internal stress, and reinforce the connection between BGA and the substrate, thereby greatly enhancing the reliability of the connection.
For example, when the mobile phone we use daily falls from a height of 2 meters, it can still work normally after being turned on, with basically no impact on its performance, except for some scratches on the shell. It's amazing, isn't it? This is because BGA underfill adhesive is used to fill BGA/CSP, making it more firmly bonded to the PCB board.
