Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Patent
1994-02-23
1997-08-12
Duda, Kathleen
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
4302811, 4302861, 430311, 430313, G03C 500, G03F 700
Patent
active
056564112
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with improvements in and relating to coating compositions. More particularly, the invention relates to so-called "resist" compositions, particularly solder resist compositions, for use in the manufacture of printed circuit boards.
Resist compositions are used, in the manufacture of printed circuit boards, to form patterned layers on the surfaces of appropriate substrates (e.g. copper-clad phenolic laminate boards) so that some areas are protected and others not protected against subsequent treatment of some sort, such as, for example, etching, plating or contact with molten solder. Resists intended for protection of parts of a substrate against solder are commonly formed solder resists.
A patterned layer of a resist may be applied to a substrate by applying a liquid in patterned form (commonly through an appropriately patterned or masked screen) and then curing the applied layer to form the final resist, for example by exposure to radiation in the case of radiation-sensitive compositions or by thermal curing in the case of thermally curable compositions. Alternatively, using a photoimaging technique, a layer of radiation sensitive (generally UV-sensitive) liquid coating is applied over the surface of the substrate and then, commonly after drying to form a tack-free film, imagewise exposed to appropriate radiation through an appropriately patterned mask. Depending on the nature of the photosensitive material in the resist composition, the effect of radiation may be to render it more soluble (a "positive-working" resist) or less soluble (a "negative-working" resist). In general, solder resists are commonly based on negative-working photosensitive materials. In either case, after exposure to irradiation, the irradiated coating is "developed" by dissolving away the more soluble portions of the coating with an appropriate solvent.
In practice, thermally curable resist systems have been generally found to give tougher, more resistant coatings than do radiation-cured materials and there have been proposed photoimageable resist compositions which also contain thermally curable components so that after photoimaging and development the patterned resist may be subjected to a final thermal cure to give a good solder-resistant coating.
Since thermally curable compositions generally comprise a thermally curable component, such as an organic resin, together with a catalyst, curing agent or cross-linking agent component potentially reactive with the thermally curable material, it has been the practice to put such compositions up as two-part packs, wherein the potentially reactive components of the composition are separated in different packs, thereby to improve the shelf-like of the product as sold. On mixing the two packs, the resultant composition has a limited shelf or product use life since some reaction of the potentially reactive components will occur, albeit slowly in some cases. This is clearly disadvantageous and also leads to further disadvantages in the case of photoimageable systems in that unwanted residues may appear after the development stage, having been produced during, for example, drying prior to irradiation of the dried coating.
It has now been found, in accordance with the present invention, that thermally curable resist systems (which may also be photoimageable) of improved shelf life and having reduced tendency to residue formation, after mixing, may be obtained by formulating them in two-part pack form and having at least one of the packs containing water, as principal carrier liquid. This has the additional, most important, benefit that the amount of volatile organic solvents employed is markedly reduced, the principal liquid carrier being the environmentally-acceptable liquid, water.
Basically, therefore, the present invention provides a two-part pack system for the preparation of a thermally-curable coating composition, one pack containing a thermally curable material and the other containing a curing system potentially reactive with the thermally curable material, i
REFERENCES:
patent: 4067838 (1978-01-01), Hayashi
patent: 4391931 (1983-07-01), Haigh et al.
patent: 4438189 (1984-03-01), Geissler et al.
patent: 4463120 (1984-07-01), Collins et al.
patent: 4548977 (1985-10-01), South, Jr.
International Search Report.
"The Chemistry of Organic Film Formers, " D.H. Solomon, Robert E. Kreiger Publishing Co. Inc., 1982, pp. 187-210.
Ivory Nicholas Eric
Thatcher Wrenford John
Coates Brothers PLC
Duda Kathleen
LandOfFree
Coating compositions and their use as solder resists does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coating compositions and their use as solder resists, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coating compositions and their use as solder resists will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-159084