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Talking about the type and selection of the adhesive
smt electronic patch processing
Type of SMD Adhesive: In smt SMD processing technology, thermosetting SMD adhesive is generally used to paste components on PCB boards. The main materials used are epoxy resin, polypropylene, nitrile propionate and Polyester and more. There are two kinds of commonly used adhesives: epoxy adhesive and acrylic adhesive.
1. Epoxy adhesive, epoxy adhesive is the most commonly used adhesive in smt chip processing. Its main components are epoxy resin, curing agent, fillers and other additives, epoxy adhesive. The curing method of sheet glue is mainly heat curing. Epoxy resin is a thermosetting, high-viscosity adhesive, which can be made into liquid, paste, film, powder and other forms. After curing, the thermosetting adhesive will not soften when heated, and cannot re-establish adhesive connections. Thermosetting can be divided into one-component and two-component.
2. Acrylic adhesive. Acrylic patch adhesive is another large type of patch adhesive commonly used in smt patch processing. Its components mainly include acrylic resin, photocuring agent and filler, which are light-curing patch adhesives. Acrylic resins are also thermosetting adhesives and are often used as one-component systems. It is characterized by stable performance, short curing time and sufficient curing, easy control of process conditions, storage conditions at room temperature and protection from light for up to one year, single bond strength and electrical properties are not as high as epoxy type.
Curing. The curing methods of the adhesive include heat curing and light curing. Photothermal dual curing and ultrasonic curing, etc., among which photocuring is rarely used alone. Ultrasonic scratching is commonly used for adhesives that use storage-type curing agents. The most commonly used curing methods in the Smt chip processing process are mainly thermal curing, ultraviolet light / thermal curing.
1. Thermal curing. Heat curing is commonly used in two types: oven intermittent heat curing and infrared furnace continuous heat curing.
2. UV / heat curing. Ultraviolet light / heat curing system is the simultaneous use of ultraviolet light irradiation and heating methods, which can cure the adhesive very quickly on continuous production lines.
The selection method of the adhesive is as follows:
(1) At present, thermosetting patch adhesives are generally used, and the equipment and process requirements are relatively simple. Since the light-solid adhesive is cured sufficiently and has high adhesion fastness, the light-solid adhesive should be selected for wider components.
(2) It is necessary to consider the performance before curing, curing performance and curing performance to meet the requirements of the surface assembly process for the surface mount adhesive.
(3) The patch adhesive with lower curing temperature and shorter curing time should be optimized. Currently, the curing conditions of the better patch adhesives are generally less than 3 minutes at 150 degrees.
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