# US 6,295,730 B1 · Method and apparatus for forming metal contacts on a substrate > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,295,730 B1 - Document ID: US6295730B1 - Status: Granted - Kind: B1 - Application number: 09/389,316 - Filed: 1999-09-02 - Granted: 2001-10-02 - Earliest claimed: 1999-09-02 - Assignees: Micron Technology, Inc. - Inventors: Salman Akram - Web page: https://patentgrep.com/patent/US6295730B1 ## CPC - H05K 3/3485: Application of solder paste, slurry or powder (using printing techniques to form the desired conductive pattern of the printed circuit by applying conductive material H05K3/12) - H10P 72/74: {using temporarily an auxiliary support} - H05K 3/3478: Application of solder preforms; Transferring prefabricated solder patterns - H05K 2203/0338: Transferring metal or conductive material other than a circuit pattern, e.g. bump, solder, printed component - H05K 2203/043: Reflowing of solder coated conductors, not during connection of components, e.g. reflowing solder paste - H10W 72/01204: {using temporary auxiliary members, e.g. using sacrificial coatings or handle substrates} - H10W 72/01225: {in solid form, e.g. by using a powder or by stud bumping} - H10W 72/07251: {characterised by changes in properties of the bump connectors during connecting} - H10W 72/20: Bump connectors, e.g. solder bumps or copper pillars; Dummy bumps; Thermal bumps - H10W 72/251: {Materials} - H10W 74/00: Encapsulations, e.g. protective coatings - Y10T 29/49117: Conductor or circuit manufacturing - Y10T 29/49126: Assembling bases - Y10T 29/49128: Assembling formed circuit to base - Y10T 29/49144: by metal fusion - Y10T 29/49147: Assembling terminal to base - Y10T 29/49149: by metal fusion bonding - Y10T 29/49155: Manufacturing circuit on or in base - Y10T 29/49165: by forming conductive walled aperture in base - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract Metal traces and solder bump pads are formed on a semiconductor substrate by way of a semiconductor template that has been micro-machined to receive solder paste material. The solder paste material is then formed into precisely-controlled ball shapes and metal trace geometries. First, a semiconductor substrate is covered with a mask material for protecting selected surfaces of the substrate that are not to be etched. Next, a mask is applied in order to etch the substrate surface below. Solder ball sites and metal trace channels are formed at this time. A solder non-wettable material is applied to the exposed surfaces of the solder ball sites and the metal trace channels. A solder paste can then be applied uniformly across the surface of the substrate, thus filling in any sites and channels, or both, that are used to form the balls in metal traces desired. The semiconductor template is then applied solder side to a second substrate so that the solder balls and traces can be applied directly on the second substrate using heat to reflow the solder to the second substrate. ## Claims ### Claim 1 A method for forming a mold for forming metal bumps on a secondary substrate, comprising: applying a protective layer to a surface of a substrate mold; masking said protective layer; removing at least a portion of said protective layer forming at least one opening in said protective layer; forming at least one cavity in said substrate mold through said at least one opening in said protective layer; forming a non-stick protective layer in said at least one cavity; and forming at least one heating strip on another surface of the substrate mold. ### Claim 2 (depends on 1) The method according to claim 1, wherien said protective layer is a silicon oxide layer. ### Claim 3 (depends on 1) The method according to claim 1, wherein said protective layer is silicon nitride layer. ### Claim 4 (depends on 1) The method according to claim 1, wherein said non-stick protective layer prevents metal material from adhering to said at least one cavity. ### Claim 5 (depends on 1) The method according to claim 1, further comprising: applying a metal paste to said substrate mold; spreading said metal paste across said surface within said at least one cavity; heating said substrate mold with said metal paste in said at least one cavity to a temperature sufficient enough to melt said metal paste; and sufficient enough to melt said metal paste; and removing said metal paste within said at least one cavity. ### Claim 6 (depends on 5) The method according to claim 5, further comprising: applying said substrate mold to said secondary substrate; using said heating for said melted solder paste to form a contact with said secondary substrate; and removing said secondary substrate from said substrate mold wherein said melted solder paste adheres to said secondary substrate and not to said at least one cavity. ### Claim 7 (depends on 1) The method according to claim 1, wherein the at least one cavity includes a trapezoidal shaped cavity. ### Claim 8 (depends on 1) The method according to claim 1, wherein the at least one cavity includes a hemispherical shaped cavity. ### Claim 9 (depends on 1) The method according to claim 1, wherein the at least one cavity includes a rectangular shaped cavity. ### Claim 10 (depends on 1) The method according to claim 1, wherein the at least one cavity includes a square shaped cavity. ### Claim 11 (depends on 1) The method according to claim 1, wherein the at least one heating strip includes a resistance heating strip. ### Claim 12 (depends on 1) The method according to claim 1, further comprising: forming a plurality of heating strips on said another surface of the substrate mold. ### Claim 13 (depends on 1) The method according to claim 1, further comprising: forming an electrical conductor having a portion connected to the at least one heating strip. ### Claim 14 (depends on 12) The method according to claim 12, further comprising: forming an electrical conductor having a portion thereof connected to the plurality of heating strips. ### Claim 15 A method for forming a mold for forming metal bumps on a secondary substrate, comprising: applying a protective layer to a surface of a substrate mold; masking said protective layer; removing at least a portion of said protective layer forming at least one opening in said protective layer; forming at least one cavity in said secondary substrate through said at least one opening in said protective layer; forming a non-stick protective layer in said at least one cavity; applying a metal paste to sid substrate mold; spreading said metal paste across said surface within said at least one cavity; heating said substrate mold with said metal paste in said at least one cavity to a temperature sufficient enough to melt said metal paste; removing said metal paste within said at least one cavity; and forming at least one heating strip on another surface of the substrate mold. ### Claim 16 (depends on 15) The method according to claim 15, further comprising: applying said substrate mold to said secondary substrate; using said heating for said melted solder paste to form a contact wth said secondary substrate; and removing said secondary substrate from said substrate mold wherein said metal solder paste adheres to said secondary substrate and not tos aid at least one cavity. ### Claim 17 (depends on 15) The method according to claim 15, wherein the at least one cavity includes a trapezoidal shaped cavity. ### Claim 18 (depends on 15) The method according to claim 15, wherein the at least one cavity includes a hemispherical shaped cavity. ### Claim 19 (depends on 15) The method according to claim 15, wherein the at least one cavity includes a rectangular shaped cavity. ### Claim 20 (depends on 15) The method according to claim 15, wherein the at least one heating strip includes a resistance heating strip. ### Claim 21 (depends on 15) The method according to claim 15, further comprising: forming a plurality of heating strips on said another surface of the substrate mold. ### Claim 22 (depends on 15) The method according to claim 15, further comprising: forming an electrical conductor having a portion connected to the at least one heating strip. ### Claim 23 (depends on 21) The method according to claim 21, further comprising: forming an electrical conductor having a portion thereof connected to the plurality of heating strips.