A, red gum
Red gum is a kind of polyene compounds, heated likely to occur after solidification, when temperature is 150 ℃, freezing point has the paste body becomes solid red glue, use this feature, you can use a little glue or printed to fixed patch components, circuit board components using patch red plastic can be heated through or reflow oven curing.
The components on the circuit board, especially the double-sided pasted circuit board, are fixed with patch red glue during wave soldering, so that the small patch components on the back can not fall out of the tin furnace. Red glue has several major characteristics:
(1) for all kinds of chip components can obtain a stable adhesive strength;
(2) with suitable for screen printing made of viscosity and rolling, the amount of glue is stable and there will be no brush leakage or tower edge;
(3) has a good preservation of stability;
(4) has high adhesion strength, can avoid high speed patch when the components offset.
Main function: the main function of red glue is to fix PCB patch elements, mainly for bonding, or used together with solder paste as reinforcement.
Second, the cement
The yellow glue used in the circuit board is a kind of water-based adhesive, with a pungent smell, is a kind of soft self-adhesive gel, has excellent insulation, moisture-proof, shock-proof and thermal conductivity, so that electronic components operate safely under harsh conditions.
It is prone to curing, curing speed and environmental temperature, humidity and wind speed: the higher the temperature, the lower the humidity, the higher the wind speed, the faster the curing speed, and vice versa. When the coated parts are placed in the air, there will be a phenomenon of skin forming slowly. Please note that the operation should be completed before the skin forming on the surface.
Main functions: fixed inductors, coils, transformers, electrolytic capacitors, receiving first-class electronic products, with the function of protecting and sealing electronic components, which can be used for filling and sealing electrical components, filling and sealing high-voltage components, moisture-proof coating of circuit boards, etc.
Three, thermal silicone
Thermal conductive silicone is also called thermal paste, cooling paste, is a kind of high thermal conductive insulation silicone material, not like thermal conductive silicone almost never cure, can be in – 50 ℃, + 250 ℃ temperature long-term use of grease. It has excellent electrical insulation, excellent thermal conductivity, low oil dispersion (tend to zero), high and low temperature resistance, water resistance, ozone resistance, weather aging. Its characteristics are non-toxic, tasteless, non-corrosive, in line with ROHS standards and related environmental protection requirements, chemical and physical properties of stability.
Main function: it is used to fill the gap between heating body and cooling device, increase their contact area, so as to achieve the thermal conductivity effect, so that the heat of electronic components can be effectively emitted and transmitted when working.
It is widely applied to the contact surface between the heating body (power tube, thyristor, electric heat reactor, etc.) and the heat dissipation facilities (heat sink, heat dissipation strip, shell, etc.) in various electronic products and electrical equipment to play the role of heat transfer medium and improve the heat dissipation effect.
Silicone gum is a kind of ointment, once exposed to the moisture in the air will solidify into a tough rubber-like solid material. Silicone adhesive is commonly used for glass adhesion and sealing, so commonly known as glass adhesive, adhesive material should be sealed storage. Mix good glue material should be used up at a time, avoid to cause waste.
Main functions: widely used in electronic modules, sensors, electronic components and other needs to be sealed, insulation, flame retardant occasions and electronic components bonding and fixed components insulation.
Five, hot melt adhesive
Hot melt glue is ethylene/vinyl acetate (EVA) polymer as main material and adding modified rosin resin or petroleum resin and other ingredients into solid adhesive, is a kind of plasticity non-toxic tasteless green environmental protection adhesive, hot melt adhesive in a certain temperature range of physical state changes with the temperature, and chemical properties remain the same. It does not contain water or solvent at all. It is characterized by rapid adhesion, high strength, aging resistance, non-toxic, good thermal stability, and film toughness.
Heat the hot melt adhesive to the service temperature, spray gun or coating on the adhesive, the adhesive must be completed in the opening time of the adhesive and finalize the work, clamping the adhesive to cool to normal temperature. Hot melt adhesive is solid at suitable temperature. It is heated and melted into liquid. It is cooled at room temperature to complete bonding within a few seconds.
Main functions: hot melt adhesive is suitable for fixing electronic components, bonding electronic wiring, and bonding other electronic materials. It can even be used for mutual adhesion and fixation of handicrafts, packaging cartons, ornaments, handicrafts, wood and textile samples.