Thermosetting solder masking film composite

Abstract

The invention provides a thermosetting solder masking film composite, which is applied to a flexible printed circuit board and comprises the following components in part by weight: (a) 50 to 100 parts of epoxy resin, b) 1 to 10 parts of hardening agent and (c) 1 to 10 parts of catalyst. The epoxy resin at least comprises an aliphatic polyester modified epoxy resin represented by the formula (I) or the formula (II), wherein R1 and R2 are saturated or unsaturated C6 to C38 carbon chains respectively; R3 is an ether, a benzene ring, a C6 to C38 heterocycle or a C6 to a C38 saturated carbon chain; n is an integer between 1 and 10; and the weight average molecular weight of the aliphatic polyester modified epoxy resin is 1,000 to 5,000.

Description

technical field [0001] The invention relates to a solder mask composition, in particular to a thermosetting solder mask composition for flexible printed circuit boards. Background technique [0002] Flexible printed circuit boards are flexible and can meet the needs of light, thin, short, and small electronic products, and are widely used in various industries such as aerospace, electrical machinery, machinery, automobiles, and electronics. Since the copper wires on the flexible printed circuit board are easily oxidized by the external environment, a protective film similar to the solder mask (SolderMask) function is needed to prevent the oxidation of the copper wires. Solder mask (also known as green paint) is a The ink composed of epoxy resin is too brittle and has poor flexibility after film formation, so it is not suitable for flexible printed circuit boards with high flexibility. [0003] Traditionally, the protective film materials used for flexible printed circuit bo...

AI Technical Summary

Problems solved by technology

Since the copper wires on the flexible printed circuit board are easily oxidized by the external environment, a protective film similar to the solder mask (SolderMask) function is needed to prevent the oxidation of the copper wires. Solder mask (also known as green paint) is a Inks composed of epoxy resins are too brittle and not flexible after film formation, so they are not suitable for flexible printed circuit boards with high flexibility

[0003] Traditionally, the protective film materials used for flexible printed circuit boards are polyimide (PI) protective films or acrylic protective films containing a layer of epoxy resin (epoxy) adhesive. Adhesive copper foil laminates will cause asymmetry in the material structure, making the flexibility of the flexible substrate poor. In addition, because the adhesive layer has poor heat resistance and large shrinkage, it will lead to soft substrates. The heat resistance and dimensional stability of the permanent substrate deteriorate

In addition, when applied to chip on flex (COF) products, it is necessary to bend and shape the flexible printed circuit board, while the traditional PI protective film containing an adhesive layer is too rigid to be used in flexible printed circuit boards. When the circuit board is bent, the recovery force is large and it is not easy to shape, so it cannot be applied to COF products

[0004] Another liquid protective film material used for flexible printed circuit boards is epoxy resin system, which needs to add rubber as a softener to improve the problem of insufficient flexibility, but the heat resistance of rubber is poor, and it is different from epoxy resin. The compatibility is not good. If too much rubber is added, the heat resistance of the protective film will deteriorate, which will cause problems in the high-temperature solder preparation process. If the rubber is not added enough, the flexibility of the protective film will become poor and brittle

[0005] In U.S. Patent No. 6,818,702 and U.S.2007 / 0088134, modification is made for the poor flexure of epoxy resin, which utilizes polybutadiene (polybutadiene) and epoxy resin (epoxy) with terminal groups containing -COOH or -OH functional groups Reaction, although good flexibility can be obtained, but its synthesis steps are complicated and its heat resistance and adhesion are not good, and it is easy to peel off from the board in the subsequent preparation process

[0006] In addition, in Japanese patents JP2006124681, JP2007246648, and U.S. patent US2007 / 0293636, it is mentioned to use polyurethane (urethane) to modify epoxy resin, polycarbonate (polycarbonate) and diisocyanate (diisocyanate) with -OH functional group, and Dimethylopropionic acid reacts to form polyurethane (PU) with -COOH functional groups and then mixes it with epoxy resin. Although it has excellent flexibility, the specific gravity of polyurethane (urethane) is too high, so that Its heat resistance and chemical resistance are not good

In addition, there is also the use of acrylic rubber to add epoxy resin to improve flexibility, but the heat resistance of acrylic is still lower than that of epoxy resin, resulting in poor heat resistance

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