# US 6,216,938 B1 · Machine and process for reworking circuit boards > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,216,938 B1 - Document ID: US6216938B1 - Status: Granted - Kind: B1 - Application number: 09/409,832 - Filed: 1999-09-30 - Granted: 2001-04-17 - Earliest claimed: 1999-09-30 - Assignees: International Business Machines Corporation - Inventors: Norman A. Card, Jr.; James M. Ergler; James D. Herard; Paul R. Kasperek; Richard S. McKinley; Der-jin Woan - Web page: https://patentgrep.com/patent/US6216938B1 ## CPC - H05K 3/3494: Heating processes for reflow soldering - B23K 1/012: Soldering with the use of hot gas - B23K 2101/42: Printed circuits - H05K 3/26: Cleaning or polishing of the conductive pattern - H05K 2203/0445: Removing excess solder on pads; removing solder bridges, e.g. for repairing or reworking - H05K 2203/045: Solder-filled plated through-hole [PTH] during processing wherein the solder is removed from the PTH after processing - H05K 2203/081: Blowing of gas, e.g. for cooling or for providing heat during solder reflowing - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS - B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM ## Abstract A method and apparatus is described for reworking a printed circuit board having plugged vias and plated through holes. The printed circuit board, supported by a movable local support, is heated from only the bottom side by a heating device near the area on the PCB that contains the plated through hole or holes to be reworked. The heating device is removed when the solder in the plugged PTH is completely melted. At that time, blast air is turned on to remove and blow off the excess solder in the PTH. The compressed air is more effective in displacing the molten solder than is vacuuming, and has less chance of damaging the PCB than do conventional reworking methods, due to the non-contact nature of the invention. ## Claims ### Claim 1 An apparatus for reworking a defective printed circuit board (PCB) having solder-plugged plated through holes (PTHs), said apparatus for cleaning said solder from said solder-plugged plated through holes, comprising: movable supporting means for carrying said defective PCB to be reworked; air supplying means disposed adjacent solder-plugged plated through holes carried by said defective PCB for providing air under pressure to said solder-plugged plated through holes of said defective area of said PCB to remove excess solder from said solder-plugged plated through holes of said defective area, and to cool said PCB; heat protective means surrounding said defective area of said PCB to prevent solder splashing upon, and damage to, non-defective areas of said PCB; heating means disposed below said PCB for locally heating said defective area to cause the solder in said solder-plugged plated through holes to melt; and control means operatively connected to said heating means and to said air supplying means, said control means operatively controlling said heating means and said air supplying means in a proper operational sequence, so that said heating means is removed during an excess solder removing and cooling cycle. ### Claim 2 (depends on 1) The apparatus in accordance with claim 1, wherein said movable supporting means is adjustable for differently sized PCBs. ### Claim 3 (depends on 1) The apparatus in accordance with claim 1, wherein said control means comprises a computer and a solenoid, said solenoid actuating said heating means and said means for supplying air under the control of said computer. ### Claim 4 (depends on 1) The apparatus in accordance with claim 1, wherein said control means comprises a timing device and a solenoid, said solenoid actuating said heating means and said means for supplying air under the control of said timing device. ### Claim 5 (depends on 1) The apparatus in accordance with claim 1, further comprising means for collecting melted solder disposed below said PCB. ### Claim 6 An apparatus for reworking a defective printed circuit board (PCB) having solder-plugged plated through holes (PTHs), comprising: movable supporting means for carrying said defective PCB containing solder-plugged plated through holes to be reworked, said movable supporting means being movable to center a defective area of said PCB below an air supplying means; air supplying means disposed above said defective PCB to supply air under pressure to said solder-plugged plated through holes of said defective area of said PCB to remove excess solder from said solder-plugged plated through holes of said defective area, and to cool said PCB; heat protective means surrounding said defective area of said PCB to prevent solder splashing upon, and damage to, non-defective areas of said PCB; heating means disposed below said solder-plugged plated through holes of said defective area of said PCB for locally heating said defective area to cause the solder in said solder-plugged plated through holes to melt; and control means operatively connected to said heating means and to said means for supplying air, said control means operatively controlling said heating means and said means for supplying air in a proper operational sequence, so that said heating means is removed during an excess solder removing and cooling cycle. ### Claim 7 (depends on 6) The apparatus in accordance with claim 6, wherein said movable supporting means is adjustable for differently sized PCBs. ### Claim 8 (depends on 6) The apparatus in accordance with claim 6, wherein said control means comprises a computer and a solenoid, said solenoid actuating said heating means and said means for supplying air under the control of said computer. ### Claim 9 (depends on 6) The apparatus in accordance with claim 6, wherein said control means comprises a timing device and a solenoid, said solenoid actuating said heating means and said means for supplying air under the control of said timing device. ### Claim 10 (depends on 6) The apparatus in accordance with claim 6, further comprising means for collecting melted solder disposed below said PCB.