Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1999-06-08
2001-07-24
Lorin, Francis J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S936000, C427S304000
Reexamination Certificate
active
06265086
ABSTRACT:
The present invention relates to a method for electroless metal deposition. Specifically, the method relates to electroless deposition of metal on a substrate having a silyl hydride functional resin coating.
Electroless plating of metals is known in the art. In this process, a metal compound is reduced to metallic state by means of a chemical reducing agent. A typical electroless plating process involves forming a plating solution of a metal salt of the metal to be plated, a suitable reducing agent, a base, a complexing agent to solubilize the metal salt and special additives to control the solution stability and plating rate. These solutions are deposited on a substrate with a catalytically active surface. This catalytically active surface catalyzes the reduction of the metal salt and results in the deposition of the metal as a film on the surface. The metal film is autocatalytic and, thus, catalyzes further reaction and deposition of additional metal.
Anderson, J. Am. Chem. Soc., 80, 5083 (1958), teaches that a silyl hydride functionality can be used as a single electron donor for the reduction of several transition metal halides to their ground metal state. The reference teaches the use of a silane as the source of the silyl hydride functionality.
Similarly, Frye et al. in U.S. Pat. No. 5,281,440 and WO 97/46326 teach a method of depositing a metal film on the surface of a solid which contains hydroxyl groups. The method described therein comprises first reacting the surface of the solid having hydroxyl groups with a silyl hydride such as a silane to form silyl hydride on the surface. Next, the silyl hydride surface is reacted with a metal ion resulting in its reduction and, thus, deposition as a metal film.
The process of the above Frye et. al. patents, however, starts with a surface which contains sufficient hydroxyl groups and these hydroxyl groups are then silylated by reaction with a silane. This limits the surfaces onto which the metal film can be applied. Moreover, this process is complicated, time consuming, expensive and it can result in the release of byproducts such as HCl. Finally, the process generally cannot provide metal tracks with high resolution.
Wagner et al., Industrial and Engineering Chemistry, vol. 44, no. 2, pp. 321 (1952) teach the production, properties and uses for silicon oxyhydride. The reference states that solutions of silicon oxyhydride can be used as reducing agents for the reduction of various metals. Likewise the reference states that silica coated with silicon oxyhydride by a process comprising hydrolyzing trichlorosilane on its surface can reduce silver and other ions. The reference does not, however, teach either applying resinous coatings from solutions which act as reducing agents for metals or forming patterned metal films on substrates.
We have now discovered a process for electroless metal deposition which avoids the problems of the prior art processes.
The present invention provides in one of its aspects a method for forming a patterned metal film on a substrate by electroless metal deposition comprising applying a patterned coating comprising a silyl hydride functional resin onto a substrate and applying an electroless plating solution comprising a metal ion onto the silyl hydride functional resin coating to deposit a patterned metal film on the substrate.
By the above method, one can apply metal films on a wide variety of substrates by simple processes. The resultant metal films can be formed with very high resolution such that they are useful in the electronics industry.
The choice of substrates to be coated in the present invention is limited only by the fact that the silyl hydride functional resin must adhere to a surface of the substrate without adversely affecting the structure of the resin or the surface of the substrate. Thus, the substrate can be, for example, glass, metal, plastic, ceramic or the like. It is preferred, however, to coat electronic substrates including, but not limited to, electronic devices or electronic circuits such as circuit boards, silicon based devices, gallium arsenide based devices, focal plane arrays, opto-electronic devices, photovoltaic cells and optical devices.
The first step in the electroless deposition of metals according to this invention comprises the activation of the substrate surface by deposition of the silyl hydride functional resin. The resin coating can be on one or more surfaces of the substrate.
The silyl hydride (Si—H) functional resin used herein can be any resin which is capable of being applied to the surface of the substrate and provide sufficient Si—H functionality at its surface to generate an effective catalytic coating for the electroless metal deposition. The structure of the resin is not specifically limited. Such resins are known in the art but have not been used for the purpose of the present invention. Generally, they have units of the structure:
R
p
HSiO
(3−p)/2
in which each R is independently an organic group or a substituted organic group, preferably a monovalent hydrocarbon group containing 1 to 20 carbon atoms such as alkyl (e.g., methyl, ethyl, propyl or butyl), alkenyl or phenyl and p is 0, 1, or 2. Such resins may also contain units of the structure:
R
n
SiO
(4−n)/2
in which R is as referred to above, and n is 0, 1, 2 or 3. Obviously, such resins must have sufficient crosslinking (i.e., units in which silicon is bonded to 3 or 4 oxygen atoms) to be resinous in structure.
The preferred silyl hydride functional resins contain units of the formula:
HSiO
3/2
These resins may be only partially hydrolyzed (i.e., containing some Si—OR′ in which R′ is an organic group or a substituted organic group (including, for example, alkyls such as methyl, ethyl, propyl, butyl, etc., aryls such as phenyl, and alkenyls such as allyl or vinyl) which, when bonded to silicon through the oxygen atom, forms a hydrolyzable substituent) and/or partially condensed (i.e., containing some Si—OH). Although not represented by this structure, these resins may contain a small number (e.g., less than about 10%) of silicon atoms which have either 0 or 2 hydrogen atoms attached thereto due to various factors involved in their formation or handling.
The most preferred silyl hydride functional resins are those which are substantially hydrolyzed and condensed and have the structure (HSiO
3/2
)
n
in which n is 3 to 10,000. These materials, known as hydrogen silsesquioxane resins, and methods for their production are known in the art. For example, Collins et al. in U.S. Pat. No. 3,615,272 teach the production of a nearly fully condensed resin (which may contain up to 100-300 ppm silanol) by a process comprising hydrolyzing trichlorosilane in a benzenesulfonic acid hydrate hydrolysis medium and then washing the resultant resin with water or aqueous sulfuric acid. Similarly, Bank et al. in U.S. Pat. No. 5,010,159 teach hydrolyzing hydridosilanes in an arylsulfonic acid hydrate hydrolysis medium to form a resin which is then contacted with a neutralizing agent. The structure of the hydrogen silsesquioxane resin may be what is generally known as ladder-type, cage-type or mixtures thereof.
Other silyl hydride functional resins, such as those described by Frye et al. in U.S. Pat. No. 4,999,397, those produced by hydrolyzing an alkoxy or acyloxy silane in an acidic, alcoholic hydrolysis medium, those described in 60-86017 and 63-107122, or any other silyl hydride functional resin, will also function herein.
The silyl hydride functional resin is applied as a coating to a surface of the substrate. The silyl hydride functional resin coating can be applied in any manner desired or practical. A preferred method involves dissolving or dispersing the resin in a diluent to form a mixture. This mixture is then applied to the surface of the substrate.
As such, a second aspect of the present invention is a method for forming a metal film on a substrate by electroless metal deposition comprising applying a mixture comprising a silyl hydride functional resin and a diluent onto a subst
Dow Corning Limited
Gobrogge Roger E.
Lorin Francis J.
Severance Sharon K.
LandOfFree
Electroless metal deposition on silyl hydride functional resin does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electroless metal deposition on silyl hydride functional resin, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electroless metal deposition on silyl hydride functional resin will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438045