Polyimide oligomer and liquid photoimagable solder resist ink

Abstract

The invention discloses a polyimide oligomer and a liquid photoimagable solder resist ink. A structural formula of the polyimide oligomer is as follows: R1 is alicyclic, R2 is alkyl with at least one carbon ring structure, n is not less than 1 and not more than 30, m is not less than 1 and not more than 30, p is not less than 1 and not more than 30, and (n+1-m-p) is more than 0, x is not less than 5 and not more than 50. The photoimagable polyimide oligomer has the advantages of excellent heat resistance, soldering resistance, golden resistance, chemical resistance, and yellowing resistance. The liquid photoimagable solder resist ink prepared from the oligomer has excellent heat resistance, soldering resistance, golden resistance, chemical resistance, yellowing resistance, insulativity, high resolution, high flexibility and high adhesion, can be used for effectively solving the problem that the liquid photoimagable solder resist ink is easy to yellow at high temperature under the processes of thermocuring, solder coating and reflow soldering, and is especially suitable for preparing white solder resist ink so as to achieve high reflecting whiteness.

Description

technical field [0001] The invention relates to a photosensitive polymer and a liquid photosensitive solder resist ink and a flexible circuit board using the photosensitive polymer. Background technique [0002] In recent years, our PCB industry has developed at a high speed of more than 15% every year, and has entered the ranks of the world's largest PCB countries. In recent years, electronic information and communication products continue to introduce new ones, and their volume keeps shrinking, but their functions keep increasing. Therefore, flexible circuit boards have to be used instead, resulting in a substantial increase in their usage. Flexible circuit board (FPC for short) provides excellent electrical performance, can meet the design needs of smaller and higher density installation, and also helps to reduce assembly processes and enhance reliability. Flexible circuit boards are the only solution to meet the miniaturization and mobility requirements of electronic pr...

AI Technical Summary

Problems solved by technology

However, due to the implementation of the lead restriction order, the use of lead-free solder is required in the manufacture of circuit boards, which puts forward higher requirements for the heat resistance of solder mask inks (280 ° C, 10s three times), novolak epoxy resin is soldered with pure tin Or when it is tinned, it will appear powerless, resulting in an increase in the scrap rate, and the heat resistance still needs to be improved

Because it contains benzene rings, it is prone to yellowing at high temperature. In some occasions where white solder resist ink is required (such as photosensitive solder resist ink for LED), the whiteness cannot meet the requirements.

In addition, novolac epoxy resin shrinks greatly after curing, and the solder mask layer tends to become brittle, resulting in a high scrap rate in the production process

And it is not resistant to bending, it is difficult to meet the folding resistance requirements of flexible boards

[0005] Use bisphenol A type epoxy resin or bisphenol F type epoxy resin or hydroxymethyl bisphenol A type epoxy resin to partially or completely replace the novolac epoxy resin as the photosensitive resin, which has a great impact on bending resistance. Improved but still not good enough, only suitable for low-end flexible boards

The shrinkage after curing has indeed been greatly improved, but unfortunately its heat resistance is always difficult to meet the requirements of users. When soldering pure tin or tin, there are more attacks on solder resistance, and the scrap rate is higher.

Compared with novolac epoxy resin, bisphenol A epoxy resin has a lower epoxy group content in the molecular structure and a lower crosslinking density, resulting in a lower heat resistance, chemical resistance and dimensional stability of the product. Limited improvement in flexibility while sacrificing other properties

[0006] CN1390898A discloses a "dilute alkali developing photosensitive imaging solder resist ink". The photosensitive resin of this invention is a modified acrylate photosensitive oligomer. The advantage is that the coating gloss is high and the appearance level of the circuit board is improved. The disadvantage is that Not enough chemical resistance and heat resistance, easy to fall off when soldering

[0007] CN1971419A "Liquid photoimaging alkali developing electronic solder resist ink and its preparation method", the photosensitive resin of this invention is a phenolic epoxy acrylic resin, the advantage is good chemical resistance and heat resistance, the disadvantage is that the bending resistance is not enough, Cannot be used on flex board

[0008] CN102417758A "Liquid Photosensitive Solder Resist Ink", the photosensitive resin of this invention is o-cresol novolac epoxy resin, which has the advantages of good chemical resistance, heat resistance and water resistance, but the disadvantage is that it is not flexible enough and cannot be used on flexible boards

[0009] CN101928378B "A Photosensitive Resin and Its Application in Preparation of Liquid Photosensitive Solder Resist Ink", the photosensitive resin of this invention is made of organic silicon modified bisphenol A type epoxy resin or organic silicon modified hydroxymethyl bisphenol A type Epoxy resin, the advantage is that the flexibility is improved, the disadvantage is that the crosslinking density is not high, the heat resistance is still not good enough, and the adhesion and physical and mechanical properties are reduced after the introduction of silicone

[0010] CN101717599B "Liquid Photosensitive Solder Resist Ink and Its Preparation Method", the photosensitive resin of this invention uses organic silicon modified phenolic epoxy resin, the advantage is that the flexibility is improved, and the heat resistance is excellent, and the disadvantage is that the adhesion after the introduction of organic silicon decline, poor moisture resistance, and poor yellowing resistance

[0011] At this stage, there is a lack of a high-performance photosensitive resin suitable for flexible boards

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