PCB News - Introduction of SMT-related anaerobic adhesive/epoxy resin

Introduction of related anaerobic adhesive/epoxy resin in smt production

Epoxy resins generally refer to organic polymer compounds containing two or more epoxy groups in the molecule. Except for a few, their relative molecular masses are not high. The molecular structure of epoxy resin is characterized by the active epoxy group in the molecular chain. The epoxy group can be located at the end, in the middle or in a cyclic structure of the molecular chain. Because the molecular structure contains active epoxy groups, they can undergo cross-linking reactions with various types of curing agents to form insoluble and infusible polymers with a three-way network structure.

★ Performance and characteristics of epoxy resin
1. Various forms. Various resins, curing agents, and modifier systems can almost adapt to the requirements of various applications on the form, and the range can be from very low viscosity to high melting point solids.
2. Convenient curing. Choose a variety of different curing agents, the epoxy resin system can almost be cured in the temperature range of 0 ~ 180 degree Celsius.
3. Strong adhesion. The inherent polar hydroxyl groups and ether bonds in the molecular chain of epoxy resins make it highly adhesive to various substances. The shrinkage of epoxy resin is low when curing, and the internal stress generated is small, which also helps to improve the adhesion strength.
4. Low shrinkage. The reaction between the epoxy resin and the curing agent used is carried out by direct addition reaction or ring-opening polymerization reaction of epoxy groups in the resin molecule, and no water or other volatile by-products are released. Compared with unsaturated polyester resins and phenolic resins, they show very low shrinkage (less than 2%) during curing.
5. Mechanical properties. The cured epoxy resin system has excellent mechanical properties.
6. Electrical performance. The cured epoxy resin system is an excellent insulating material with high dielectric properties, surface leakage resistance, and arc resistance.
7. Chemical stability. Generally, the cured epoxy resin system has excellent alkali resistance, acid resistance and solvent resistance. Like other properties of the cured epoxy system, the chemical stability also depends on the selected resin and curing agent. Appropriate selection of epoxy resin and curing agent can make it have special chemical stability.
8. Dimensional stability. The combination of many of the above properties gives the epoxy resin system outstanding dimensional stability and durability.
9. Resistant to mold. The cured epoxy resin system is resistant to most molds and can be used in harsh tropical conditions.
★ Classification
According to the molecular structure, epoxy resins can be roughly divided into five categories:
1. Glycidyl ether epoxy resin
2. Glycidyl ester epoxy resin
3. Glycidylamine epoxy resin
4. Linear aliphatic epoxy resin
5. Alicyclic epoxy resin
The most widely used epoxy resins in the composite material industry are the above-mentioned glycidyl ether epoxy resins, and among them, diphenol-based propane epoxy resins (referred to as bisphenol A epoxy resins) are the main ones. The second is glycidylamine epoxy resin.
1. Glycidyl ether epoxy resin
Glycidyl ether epoxy resin is formed by polycondensation of phenols or alcohols containing active hydrogen with epichlorohydrin.
(1) Diphenol-based propane epoxy resin Diphenol-based propane epoxy resin is formed by polycondensation of diphenol-based propane and epichlorohydrin.
Industrial diphenol-based propane epoxy resin is actually a mixture of molecules with different degrees of polymerization. Most of the molecules are linear structures with two epoxy end groups. A small number of molecules may be branched, and a very small number of molecules terminate with a chlorohydrin group instead of an epoxy group. Therefore, the epoxy group content and chlorine content of the epoxy resin have a great influence on the curing of the resin and the performance of the cured product. The control indicators used as resin in industry are as follows:
1. Epoxy value. Epoxy value is the main indicator to identify the properties of epoxy resin. Industrial epoxy resin models are distinguished by different epoxy values. The epoxy value refers to the amount of epoxy groups per 100 g of resin. The reciprocal of the epoxy value multiplied by 100 is called the epoxy equivalent. The meaning of epoxy equivalent is: the number of grams of epoxy resin containing 1 mol of epoxy groups.
2. Inorganic chlorine content. The chloride ion in the resin can complex with the amine curing agent to affect the curing of the resin, and also affect the electrical properties of the cured resin. Therefore, the chlorine content is also an important indicator of the epoxy resin.
3. Organic chlorine content. The content of organochlorine in the resin indicates the content of the part of the chlorohydrin group in the molecule that has not undergone ring-closure reaction. Its content should be reduced as much as possible, otherwise it will also affect the curing of the resin and the performance of the cured product.
4. Volatile matter.
5. Viscosity or softening point.
(2) Phenolic polyepoxy resins Phenolic polyepoxy resins include phenol-formaldehyde type and o-cresol-formaldehyde type polyepoxy resins. Compared with diphenol-based propane type epoxy resins, the linear molecules contain more than two The epoxy group has high crosslinking density after curing, and has excellent thermal stability, mechanical properties, electrical insulation, water resistance and corrosion resistance. They are made by polycondensation of novolac resin and epichlorohydrin.
(3) Other polyhydroxy phenolic glycidyl ether type epoxy resins have practical representatives: resorcinol type epoxy resin, resorcinol-formaldehyde type epoxy resin, tetraphenol ethyl Alkyl type epoxy resin and trihydroxyphenylmethane type epoxy resin. These multifunctional glycidyl ether resins have high heat distortion temperature and rigidity after curing, and can be used alone
Or it can be blended with general-purpose E-type resin for use as matrix materials such as high-performance composite materials (ACM) and printed circuit boards.
(4) Aliphatic polyol glycidyl ether type epoxy resin aliphatic polyol glycidyl ether molecule contains two or more epoxy groups, most of these resins have low viscosity; most of them are long-chain Linear molecules, so flexible.
2. Other types of epoxy resin
(1) Compared with glycidyl ester epoxy resin, glycidyl ester epoxy resin and diphenol-based propane epoxidized resin, it has low viscosity, good processability, high reactivity, and better adhesion than general epoxy resin. High, the cured product has good mechanical properties; good electrical insulation; good weather resistance, and has good ultra-low temperature resistance. Under ultra-low temperature conditions, it still has higher bonding strength than other types of epoxy resins. It has good surface gloss, good light transmission and weather resistance.
(2) Glycidylamine epoxy resin The advantages of this type of resin are multifunctionality, high epoxy equivalent, high crosslinking density, and significantly improved heat resistance. The company has used the superior adhesion and heat resistance of glycidyl amine epoxy resin to manufacture carbon fiber reinforced composite materials (CFRP) for aircraft secondary structural materials.
(3) Alicyclic epoxy resins are epoxy resins made by epoxidizing double bonds of alicyclic olefins. Their molecular structure is similar to that of diphenol-based propane epoxy resins and other epoxy resins. There is a big difference. The epoxy groups of the former are all directly connected to the alicyclic ring, while the epoxy groups of the latter are all connected to the benzene nucleus or aliphatic hydrocarbon with glycidyl ether. The cured product of cycloaliphatic epoxy resin has the following characteristics: 1. higher compression and tensile strength; 2. long-term exposure to maintain good mechanical properties under high temperature conditions; 3. arc resistance, UV aging resistance and Weather resistance is better.
(4) Aliphatic epoxy resin The molecular structure of this type of epoxy resin not only has no benzene nucleus, but also has no alicyclic structure. There are only aliphatic chains, and the epoxy groups are connected to the aliphatic chains. The epoxidized polybutadiene resin has good strength, toughness, adhesion and resistance to positive and negative temperatures after curing.

The above is the introduction of SMT-related anaerobic adhesive/epoxy. Ipcb also provides PCB manufacturers and PCB manufacturing technology.