Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2001-09-10
2004-03-30
Hamilton, Cynthia (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
C522S071000
Reexamination Certificate
active
06713230
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a novel photosensitive resistive ink composition, which can be used for forming a permanent protective mask, such as solder resist or the like, to be employed for the production of printed circuit boards (printed wiring boards), has high sensitivity and high resolution (line width 50 &mgr;m) and high speed curability to a ultraviolet irradiation, and is developable with a dilute alkaline aqueous solution and forms by curing a dry film excellent in electroless gold plating resistance, soldering heat resistance, electrical characteristics and mechanical characteristics. In addition, it's easy to inspect the appearance by a formed photoresist film having a bright and transparent property.
BACKGROUND OF INVENTION
Due to the recent trend toward smaller size and higher functionality of electronic equipment and apparatus and toward higher connection density, higher pin and refinement of electronic packing technology, solder mask has been required to be of higher resolution, accuracy and reliability to match the refined surface mount technology. Various improvements in the solder mask have been proposed. Solder mask has been improved from a screen printing method having low resolution and high pollution disadvantages to a liquid photo-imaginable solder mask method developable with a dilute alkaline aqueous solution and having high resolution and low pollution advantages. However, there are many drawbacks in the liquid photo-imaginable solder mask. For instance, U.S. Pat. No. 4,943,516 proposes a resin composition comprising an undissolved epoxy compound to improve photosensitivity and decrease to react with a curing agent. A photo-curable prepolymer has a higher acid value to dissolve in a dilute alkaline aqueous solution, but it causes the poor resistance to plating. Moreover, because of the network structure after photoreaction, the undissolved epoxy compound reduces the opportunity of reacting with a curing agent to cause the poor resistance to heat.
BRIEF SUMMARY OF THE INVENTION
The major object of this invention is to overcome the drawbacks mentioned above and to provide a novel photosensitive resist ink composition useful as a liquid photo-imaginable solder mask, which has superior ultraviolet curability, soldering eat and chemical resistance, electroless gold plating resistance, flexibility, electrical characteristics and is developable with a dilute alkaline aqueous solution and also has bright and transparent appearance.
This invention relates to a liquid photosensitive resistive ink composition developed with a dilute alkaline aqueous solution, which comprises:
(A) a photo-curable prepolymer represented by the formula I, obtained by the reaction of (a) epoxy resin containing at least two terminated epoxy groups and (b) a,&bgr;-unsaturated monocarboxylic acid containing at least one vinyl group, and then reacting (c) a saturated or unsaturated polybasic acid anhydride.
(B) a photo-curable monomer containing at least three vinyl groups and an a,&bgr;-unsaturated carboxylic acid represented by the formula II,
(C) a photo-initiator,
(D) organic solvents,
(E) an epoxy compound containing at least one vinyl group and one epoxy group in the molecular unit represented by the formula III,
(F) a curing agent capable of allowing a prepolymer (A) undergo a thermal reaction, and
(G) a clay nano-composite.
DETAILED DESCRIPTION OF THE INVENTION
One characteristic of the invention is in the prepolymer (A) comprises at least one vinyl group in a molecular unit. The vinyl group increases the photocuring strength, resolution and resistance to plating of a liquid photo-imageable solder mask. In addition, the photo-curable monomer (B) of the invention comprising hydrophilic carboxylic acid group increase the solubility difference between the exposed area and unexposed area. And it can increase the developability and resolution. Moreover, the epoxy compound (E) containing at least one vinyl group and one epoxy group in the molecular unit offers steric hindrance which prevents the reaction (E) with a curing agent and a photo-curable pre-polymer. The vinyl group of the compound (E) can be reacted with the photocurable prepolymer to increase the opportunity of the thermal reaction during curing and to enhance heat resistance. The compound (E) can be dissolved in organic solvents and a dilute alkaline aqueous solution to make the appearance bright and crystalline and to be easy to develop.
The liquid photo-curable pre-polymer (A) of the invention by the formula (I) as follow, which is a reaction product obtained by reacting (a) an epoxy resin containing at least two terminated epoxy groups and (b) an unsaturated monocarboxylic acid containing at least one vinyl group, and then reacting with a saturated or unsaturated carboxylic acid anhydride.
m,n: repeating units, represented by integers as m+n≦20
R
1
: —H, —CH
3
—CH
2
—CH
2
—, —CH═CH—
(a) of at least two epoxy compounds which can be used in this invention are represented as phenol novolac epoxy resins, cresol novolac epoxy resins, halogenated phenol novolac epoxy resins. Among these epoxy resins, phenol novolac epoxy resins and cresol novolac epoxy resins are preferred.
(b) &agr;,&bgr;-unsaturated monocarboxylic acid containing at least one vinyl linkage can be included as: acrylic acid, methacrylic acid, crotonic acid and cinnamic acid. Among these unsaturated monocarboxylic acid mentioned above, acrylic acid is particularly preferable.
The saturated or unsaturated anhydride (c) can be selected from succinic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride and maleic anhydride. Among these saturated or unsaturated anhydride mentioned above, tetrahydrophthalic anhydride is particularly preferable.
According to above mentioned discussion, the amount and ratio of each component could get the best result in the following region. In the reaction, the suitable proportion of an unsaturated monocarboxylic acid containing at least one vinyl group taking part in the reaction is 0.5 to 1.2 mole, preferably 0.9 to 1.1 mole, to 1 equivalent of the epoxy groups of the epoxy compound. The proportion of polybasic acid anhydride (c) is 0.1 to 1.0 mole, preferably 0.3 to 0.5 mole, to 1 equivalent of the hydroxyl group produced by reacting above-mentioned acid with the epoxy compound.
The liquid photo-curable prepolymer (A) of this invention is obtained by the reaction of an epoxy resin containing at least two terminated epoxy groups and an &agr;,&bgr;-unsaturated monocarboxylic acid containing at least one vinyl group. In the reaction, the suitable examples of a catalyst which can be used in this invention include triphenylphosphine, triethylamine, methyl triethyl ammonium chloride and so on, preferably triphenyl phosphine. The catalyst may be used preferably in the amount of 0.1 to 10 parts by weight. In order to prevent polymerization, add thermal polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether preferably. The thermal polymerization inhibitor may be added preferably in the amount of 0.01 to 1 part by weight, per 100 parts by weight of the reaction mixture. The suitable reaction temperature and reaction time may be controlled between 80 and 120° C., 6 and 24 hours, separately. In addition, in the above mentioned reaction product reacting with a saturated or unsaturated polybasic acid anhydride, the suitable reaction temperature and reaction time may be controlled between 80 and 130° C., 4 and 16 hours, separately.
The acid value of the photo-curable prepolymer (A) so obtained suitably falls in the range of 20 to 120 mg KOH/g, preferably 30 to 80 mg KOH/g.
The photo-polymerizable prepolymer (A) in the invention can be used in an amount of 10 to 80 parts by weight, preferably 30 to 50 parts by weight of liquid photosensitive resistive ink composition.
The photo-curable monomer (B) containing at least three vinyl groups and an &agr;,&bgr;-unsaturated carboxylic acid is prepared by reacting dipentaerythritol pentaa
Chang Chi-Ming
Chao Cheng-Li
Lu Hsiao-Loung
Su Chung-Chi
Tsao Chun-Che
Bacon & Thomas PLLC
Hamilton Cynthia
Nan Ya Plastics Corporation
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