Pressurized injection nozzle for screening paste

• US 5,565,033 A
• Filed: 05/24/1995
• Issued: 10/15/1996
• Est. Priority Date: 12/21/1993
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gaynes, Michael A., Pierson, Mark V., Zalesinski, Jerzy, Oxx, George D.
• Primary Examiner(s): Czaja, Donald E.
• Assistant Examiner(s): LEAVITT, STEVEN
• Application Number:
  US08/448,958
• Time in Patent Office: 510 Days
• Field of Search: 118/210, 118/213, 118/323, 118/410, 118/406, 118/401, 118/211, 118/684, 118/413, 118/301, 427/96, 427/282, 427/259, 427/294, 425/546, 425/812
• US Class Current: 118/210
• CPC Class Codes: B23K 2101/36 Electric or electronic devices
• CPC Class Codes: B23K 3/0692 with intermediary means for bringing solder on workpiece, e.g. rollers
• CPC Class Codes: H01L 21/4853 Connection or disconnection of other leads to or from a metallisation, e.g. pins, wires, bumps
• CPC Class Codes: H01L 21/4867 Applying pastes or inks, e.g. screen printing H01L21/486 takes precedence
• CPC Class Codes: H01L 2224/2919 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/8319 Arrangement of the layer connectors prior to mounting
• CPC Class Codes: H01L 2224/838 Bonding techniques
• CPC Class Codes: H01L 24/27 Manufacturing methods
• CPC Class Codes: H01L 24/83 using a layer connector
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01077 Iridium [Ir]
• CPC Class Codes: H01L 2924/01082 Lead [Pb]
• CPC Class Codes: H01L 2924/014 Solder alloys
• CPC Class Codes: H01L 2924/0665 Epoxy resin
• CPC Class Codes: H01L 2924/0781 being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01L 2924/3025 Electromagnetic shielding
• CPC Class Codes: H05K 2201/0989 Coating free areas, e.g. areas other than pads or lands free of solder resist
• CPC Class Codes: H05K 2203/0126 : Dispenser, e.g. for solder paste, for supplying conductive paste for screen printing or for filling holes
• CPC Class Codes: H05K 2203/043 : Reflowing of solder coated conductors, not during connection of components, e.g. reflowing solder paste
• CPC Class Codes: H05K 2203/0568 : Resist used for applying paste, ink or powder
• CPC Class Codes: H05K 2203/0577 : Double layer of resist having the same pattern
• CPC Class Codes: H05K 3/1233 : Methods or means for supplying the conductive material and for forcing it through the screen or stencil
• CPC Class Codes: H05K 3/321 : by conductive adhesives
• CPC Class Codes: H05K 3/3452 : Solder masks
• CPC Class Codes: H05K 3/3485 : Applying solder paste, slurry or powder thick film methods for applying conductive paste or ink patterns H05K3/12
• CPC Class Codes: Y10T 29/49165 : by forming conductive walled aperture in base
• CPC Class Codes: Y10T 428/24917 : including metal layer

Abstract

A method of applying bonding agents, such as solder pastes and conductive adhesives, to pad sites in the manufacture of electronic circuits uses a paste injection head. A permanent mask with cavity openings is applied around conductive pads on a carrier. The conductive pads correspond to chip attachment sites. The injection head is brought into contact with a surface of the mask, and pressure is applied to a bonding agent in the injection head. The injection head is then moved over the surface of the mask, filling cavity openings with the bonding agent. The injection head is then removed from the surface of the mask. If a solder paste is used, infrared radiation is applied to filled cavity openings to evaporate a paste flux and reflow solder to form solder balls within the cavity openings projecting above the mask. If a conductive adhesive is used, a stencil is applied to the surface of the mask prior to contacting the mask with said injection head. When the cavity openings are filled, stencil is removed from the mask and the conductive adhesive filling the cavity openings is dried.

Claims

1. A pressurized injection nozzle for screening paste onto a surface with cavities or blind holes, comprising:

a nozzle including a pair of nozzle lips cooperating to form a narrow, elongate nozzle slit and sufficiently compliant to move across the surface without damaging the surface as pressure is applied between the nozzle and the surface to contain the paste;

means for supplying pressurized paste through the slit into the cavities or holes; and

an exhaust defined by a path, closer to the slit than a width of a cavity or blind hole, for allowing air to escape from cavities or blind holes as they are filled with paste.

2. A pressurized injection nozzle as recited in claim 1 wherein said elongate nozzle slit is formed by a thin leading lip and a wide trailing lip, said wide trailing lip acting as a squeegee.

3. A pressurized injection nozzle as recited in claim 2 wherein said path defining the exhaust is within said nozzle and is formed by a rigid leading lip and said thin leading lip.

4. A pressurized injection nozzle as recited in claim 3 wherein said wide trailing lip is a rigid lip.

5. A pressurized injection nozzle as recited in claim 3 wherein said wide trailing lip is a flexible lip.

6. A pressurized injection nozzle as recited in claim 1, wherein said means for supplying pressurized paste supplies a paste of solder particles in a flux carrier.

7. A pressurized injection nozzle as recited in claim 1, wherein said means for supplying pressurized paste supplies a paste of electrically conductive particles mixed in a thermoplastic and a solvent carrier.

8. A pressurized injection nozzle for screening paste onto a surface with cavities or blind holes, comprising:

a nozzle including a pair of flexible nozzle lips cooperating to form a narrow, elongate nozzle slit and sufficiently compliant to move across the surface without damaging the surface as pressure is applied between the nozzle and the surface to contain the paste; and

means for supplying pressurized paste through the slit into the holes, said lips parting under pressure between the nozzle and the surface to form the slit and pass paste under pressure to fill the cavities or blind holes, said lips closing to prevent passage of said paste when pressure between the nozzle and the surface is removed.

9. A pressurized injection nozzle for screening paste onto a surface with cavities or blind holes, comprising:

a nozzle including a pair of flexible nozzle lips cooperating to form a narrow, elongate nozzle slit and sufficiently compliant to move across the surface without damaging the surface as pressure is applied between the nozzle and the surface to contain the paste; and

means for supplying pressurized paste through the slit into the holes, said lips parting under pressure of the pressurized paste to form the slit and pass the paste to fill the cavities or blind holes, said lips closing to prevent passing of the paste when pressure on the paste is removed.

10. An apparatus for screening a bonding agent paste onto a surface of a circuit board with cavities or blind holes, comprising:

a wiping guide adapted to move across the surface without damaging the surface;

a blade which cooperates with the wiping guide to form a narrow slit;

means for supplying a pressurized paste through the slit;

an exhaust path positioned closer to the slit then a width of the holes; and

means for moving the nozzle across the surface in a direction perpendicular to the slit.