Several types of glue are commonly used for circuit boards: red glue, yellow glue, thermally conductive glue, silicone glue, hot melt glue, etc., which are used for fixing, insulation, or heat conduction. This article makes a summary for friends in the industry. For reference.

1. Red glue

Red glue is a polyolefin compound that easily solidifies when heated. When the temperature reaches 150 At the freezing point of ℃, the red glue begins to change from a paste to a solid. Using this characteristic, you can use glue dispensing or printing to fix the patch components. Circuit board components use patches. Red glue can be heated and solidified by oven or reflow soldering.

The components on the circuit board, especially the double-sided circuit board, are fixed with SMD red glue during wave soldering, so that the small SMD components on the back will not fall to the tin In the furnace. Red glue has several major features:

① Stable adhesion strength can be obtained for various chip components;

② It is suitable for screen printing Made into the required viscosity and thixotropy, the amount of glue added is stable without leakage or tower edges;

③Has good storage stability;

④Has High adhesive strength can avoid component misalignment during high-speed placement.

Main function: The main function of red glue is to fix circuit board patch components, mainly for bonding, or used together with solder paste for reinforcing fixation.

2. Yellow glue

The yellow glue used in circuit boards is a water-based adhesive with a pungent odor. This kind of soft self-adhesive gel has excellent insulation, moisture-proof, shock-proof and thermal conductivity properties, allowing electronic components to operate safely under harsh conditions.

It is prone to curing, and the curing speed is related to the ambient temperature, humidity and wind speed: the higher the temperature, the lower the humidity, the greater the wind speed, the faster the curing speed, and vice versa.

When the painted parts are placed in the air, skin will slowly form. Please note that the operation should be completed before the surface forms skin.

Main functions: inductors, coils, transformers, electrolytic capacitors, receiving heads and other electronic products fixed, with protective seal electronicsComponent function, it can be used for potting of electrical components, potting of high voltage components, moisture-proof coating of circuit boards, etc.

3. Thermal conductive silica gel

Thermal conductive silica gel, also known as thermal paste and thermal paste, is a high thermal conductivity insulating silicone material that is not as thermally conductive as Silicone grease almost never solidifies, and can maintain the grease state during use for a long time at temperatures of -50°C to +250°C.

It has both excellent electrical insulation and thermal conductivity. It also has low oil separation (tending to zero), high and low temperature resistance, water resistance, ozone resistance, and weather aging resistance.

It is characterized by being non-toxic, odorless and non-corrosive, compliant with ROHS standards and related environmental protection requirements, and has stable chemical and physical properties.

Main function: used to fill the gap between the heating element and the heat dissipation device, increase their contact area, thereby achieving the best thermal conductivity effect, so that the heat of the electronic components can be effectively dissipated and transferred when the electronic components are working. go out.

It is widely used in heating elements (power tubes, thyristors, electric heating piles, etc.) and heat dissipation facilities (heat sinks, heat sinks, etc.) in various electronic products and electrical equipment. The contact surface between strips, shells, etc.) acts as a heat transfer medium and can improve the heat dissipation effect.

4. Silicone glue

Silicone glue is a kind of ointment. Once it comes into contact with moisture in the air, it will solidify into a tough Rubber-like solid material.

Silicone glue is commonly known as glass glue because it is often used for bonding and sealing glass. The glue should be stored sealed.

The mixed rubber should be used up at one time to avoid waste.

Main functions: widely used in electronic modules, sensors, electronic components and other occasions that require encapsulation, insulation, flame retardancy, as well as bonding and fixing of electronic components. insulation etc.

5. Hot melt adhesive

Hot melt adhesive strips are made of ethylene vinyl acetate polymer (EVA) It is a solid adhesive composed of modified rosin resin or petroleum resin and other ingredients as the main material. It is a plastic, non-toxic, tasteless, green and environmentally friendly adhesive. The physical state of the hot melt adhesive changes with the temperature within a certain temperature range. change, while the chemical properties remain the same.

It does not contain water or solvent at all, and has the characteristics of fast bonding, high strength, aging resistance, non-toxicity, good thermal stability and film toughness.

Heat the hot melt glue to the use temperature, use a spray gun or apply it on the adherend. The bonding and shaping work must be completed within the opening time of the glue. Clamp the adherend and cool it to Normal temperature.

Hot melt adhesive is solid at a moderate temperature. It melts into a liquid when heated. After cooling at room temperature, it completes the bonding within a few seconds and can effectively fix electronic components and wiring harnesses.

Main functions: Hot melt adhesive is suitable for fixing electronic components, bonding electronic wiring, and can also be used for bonding other electronic materials. It can even be used to bond handicrafts, packaging cartons, jewelry, handicrafts, wood, textile samples, etc. to each other.