manufacture of electronic parts

Details manufacture of electronic parts manufacture of electronic parts

2000-10-10

2002-09-17

Baxter, Janet (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Radiation sensitive composition or product or process of making

C430S311000, C430S317000, C430S318000, C430S325000, C430S330000

Reexamination Certificate

active

06451502

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electronic parts and to their production using negative working radiation sensitive compositions.
2. Background Information
We have developed novel radiation sensitive compositions and in our earlier-filed U.S. Pat. Nos. 5,372,907 and 5,919,601 we disclosed these novel compositions and their use as imagable coatings for lithographic printing form precursors. We later determined that such compositions are suitable as radiation sensitive coatings for printed circuit and other electronic part precursors. However they are not optimal for use as coatings on all electronic part precursors. In particular, they are not optimal for use as coatings on thin, flexible substrates which are the precursors for some electronic parts and they are not flexible substrates which are the precursors for some electronic parts and they are not optimal for use on substrates required to be coated and imaged on both sides. For such applications we have sought a composition which can better withstand flexure and surface contact, without becoming scratched, cracked, flaked or delaminated. We have now devised a particular class of heat sensitive compositions which are extremely suitable for such applications.
The coatings used in pattern forming methods for electronic parts such as printed circuits are classified into two types: negative working and positive working. After exposure to radiation and development, the coating pattern is used as a screen for forming the patterns onto the underlying electronic elements—for example by etching an underlying copper foil. Due to the high resolution demands and the requirements of high resistance to etching techniques, positive working systems are widely used. In particular, in the main there have been used alkali developable positive working coatings mainly composed of alkali-soluble novolac resins as disclosed in J.C. Streiter, Kodak Microelectronics Seminar Proceedings, 1979, p. 116. The primary active component of such positive working compositions, both in the context of lithographic printing forms and electronic parts, is a naphthoquinonediazide (NQD) derivative.
The types of electronic parts whose manufacture may use a radiation sensitive coating include printed wiring boards (PWBs), thick- and thin-film circuits, comprising passive elements such as resistors, capacitors and inductors; multichip devices (MDCs); integrated circuits (ICs); and active semiconductor devices. The electronic parts may suitably comprise conductors, for example: copper board; semiconductors, for example silicon or germanium; and insulators, for example silica as a surface layer with silicon beneath, with the silica being selectively etched away to expose portions of the silicon beneath (a step in the manufacture of, e.g., field effect transistors).
In U.S. Pat. No. 5,372,907 there is described a radiation-sensitive composition for a lithographic printing plate. The composition can be used in positive-working and negative-working manners. The composition comprises a resole resin, a novolac resin, a latent Bronsted acid and an infra-red absorber. The negative-working method involves imagewise exposure to activating radiation, heating overall to effect cross-linking selectively in those regions which had been imagewise exposed, and development to selectively remove the other regions. This composition and method gives excellent imaging for printing plates, and is in commercial use. However, it is unsuitable for use in the field of electronic part manufacture because PCB substrates would not withstand flexure and surface contact without becoming scratched, cracked, flaked or delaminated.
U.S. Pat. No. 5,919,601 describes similar technology, involving use of a composition comprising a binder resin, a cross-linking resin and a thermally activated acid generator as a printing plate coating. The plates were imaged using IR radiation, then heated overall to produce the required cross-linking reactions, then developed, to remove the regions which had not received the IR radiation. Again, imaging properties are believed to be good but mechanical properties are believed to be inadequate for applications involving the manufacture of electronic parts, such as PCBs.
U.S. Pat. No. 5,527,659 describes a chemical amplification resist composition comprising a binder, a photochemical acid generator, and a squarylium compound. Example 1 describes its coating onto a grained and anodised plate. The binder was poly-p-hydroxystyrene. It was subjected to radiation of wavelength of 630 nm, then heat treated, then developed, then inked up, for printing. Other binders are also described.
EP 819985A describes negative-working lithographic printing plates having a phenolic hydroxy group-containing resin, a latent Bronsted acid, an infra-red absorber and an amino cross-linking agent. The plates are subjected imagewise to infra-red radiation, then subjected to post-exposure bake, prior to development to remove non-imaged areas. Suitable resins are said to include novolacs and polyvinylphenols. EP 819980A is a very similar disclosure, where the infra-red absorber is carbon black. Suitable resins are stated to include novolacs, polyvinylphenols and phenolic hydroxy functionalized derivatives of poly(meth)acrylates, which can be synthesized starting from, for example, hydroxyethyl(meth)acrylate.
U.S. Pat. No. 5,814,431 describes a negative-working photosensitive resin used for a lithographic printing plate, and comprising a novolac or polyvinyl phenol resin, an amino compound able to cure the composition, a defined cyanine or polymethine compound able to absorb near infra-red radiation, and a photosensitive acid-forming generator. When a polyvinyl phenol resin is used an unsubstituted polyvinyl phenol resin is preferred, but hydroxyl groups thereof are protected by t-butoxycarbonyl, pyranyl or furanyl groups. Imaging involves laser irradiation, typically at 830 nm, a post-exposure bake, and development, to remove the regions which had not been struck by the laser beam. The plates are said to have good stability, good sensitivity and good inking-up properties.
U.S. Pat. No. 5,725,994 discloses novel negative-working photosensitive compositions useful for making heat mode lithographic printing plates. The compositions comprise an acid precursor, a particular hydroxyimide compound, and a hydroxyl group-containing linear polymer. The linear polymer may be an acrylate polymer. Imaging involves delivery of light, for example from a mercury lamp, then the heating of the imaged part, prior to development.
EP-A-899614 discloses a negative-working image recording material having excellent storability, and suitable for printing plate production. The material includes a specified diazonium salt, an infra-red absorber, and acid-triggered cross-linking agent and a binder. The binder may be selected from a wide range of polymers, including novolacs and acrylates. Imaging involves imagewise delivery of infra-red radiation followed by a post-exposure bake of short duration, prior to development.
EP-A-874282 describes negative-working image recording materials comprising a heat-triggered acid generator, an acid-triggered cross-linking agent, a binder polymer and an infra-red absorber. The materials are said to be for a lithographic printing plate, a color proof, a photoresist or a color filter, and are claimed to have a high sensitivity. In the general description a very wide range of binder polymers is described. In the examples, which are all of lithographic printing plates, the binder polymers employed are phenol resins, styrenic resins and methacrylate resins, of various structures.
WO 97/39894 describes a printing plate having a positive-working heat-imagable coating, comprising a polymeric component, an insolubilizer compound and, preferably, an IR absorber. WO 99/08879 describes the use of such a coating in the manufacture of electronic parts, for example PCBs. WO 00/20222 describes improvements to that technology. To improve mechanical properties, su

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