Automated soldering process and apparatus

• US 4,595,816 A
• Filed: 08/31/1984
• Issued: 06/17/1986
• Est. Priority Date: 08/31/1984
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Hall, Richard L., Strong, David G., Silcott, Edward N., Jenniches, Frieda S., Kehoe, James R.
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US06/645,954
• Time in Patent Office: 655 Days
• Field of Search: 219/121 LC, 219/121 LD, 219/121 L, 219/121 LM, 219/85 R, 219/85 BA, 219/85 BM, 219/85 F, 228/102, 228/179, 228/180.1, 228/33, 228/43, 228/232, 364/475, 364/477
• US Class Current: 219/121.64
• CPC Class Codes: B23K 1/0056 soldering by means of beams, e.g. lasers, E.B.
• CPC Class Codes: B23K 1/08 Soldering by means of dipping in molten solder
• CPC Class Codes: B23K 2101/42 Printed circuits
• CPC Class Codes: B23K 3/063 for wire feeding
• CPC Class Codes: H05K 2203/0113 Female die used for patterning or transferring, e.g. temporary substrate having recessed pattern
• CPC Class Codes: H05K 2203/0338 Transferring metal or conductive material other than a circuit pattern, e.g. bump, solder, printed component affixing a prefabricated conductor pattern H05K3/20
• CPC Class Codes: H05K 2203/041 Solder preforms in the shape of solder balls soldering leadless components having an array of bottom contacts H05K3/3436
• CPC Class Codes: H05K 2203/0415 Small preforms other than balls, e.g. discs, cylinders or pillars
• CPC Class Codes: H05K 3/3447 Lead-in-hole components H05K3/3415 takes precedence
• CPC Class Codes: H05K 3/3478 Applying solder preforms; Transferring prefabricated solder patterns

Abstract

An automated program controlled discrete soldering system for plated holes of a printed wiring board, having a crucible for holding a discrete amount of solder and operable to travel in a substantial vertical path to a soldering position beneath the board. The solder is metered and deposited in the crucible prior to each application of laser energy to the crucible for melting the solder.

Claims

1. A method of soldering under computer program control conductive leads of electronic components in metallic-plated holes of a printed wiring board, where the components are mounted on an upper side of the board and their conductive leads extend into respective holes toward the underside of the board, said method comprising

(1) positioning a crucible beneath and spaced a predetermined distance from a selected hole of the printed wiring board,

(2) depositing a selected volume of non-molten solder in the crucible, said volume being selected to make a single soldered joint,

(3) controlling a laser beam to heat the crucible and the solder in the crucible to a selected required temperature above the molten state,

(4) placing the crucible in a position to abut the underside of the printed wiring board with the molten solder therein immersing the conductive lead and pad adjacent the hole,

(5) maintaining the crucible in the last described position until the molten solder extends into the hole and on the upper side of the printed wiring board,

(6) withdrawing the crucible to increase the space between the crucible and the underside of the board to the predetermined distance of step (1), and

(7) repeating steps (2) through (6) for another through-hole of the printed wiring board.

2. A method according to claim 1 wherein the step of depositing the solder in the crucible, comprising

shearing the selected volume of solder from a spool of flux core solder, and

transporting the sheared solder to a predetermined position above the crucible for depositing it therein.

3. A method according to claim 1 wherein the step of controlling the laser comprises

selecting the beam power and pulse length to obtain the required temperature of the molten solder.

4. A method according to claim 3 wherein the step of selecting the beam power and pulse length comprises

generating laser power at a first level to melt the solder, and

generating laser power at a second level to cause the solder to maintain proper temperature.

5. A system for soldering conductive leads of electronic components in metallic-plated holes of a printed wiring board, comprising

means to hold a printed wiring board in a position such that the components thereon are on the top of the board and the conductive leads extend downwardly in the holes to the underside of the board,

a crucible mounted beneath the board operable to hold a piece of solder and to move in a vertical position into and out of soldering position relative to the board,

a solder feeding means for positioning a length of solder for shearing by a shearing means,

shearing means mounted beneath the board operable to cut off a piece of solder from a spool of solder,

solder transport means operable to deposit a sheared piece of solder in the crucible,

laser energy means operable to direct a laser beam for melting a sheared piece of solder in the crucible,

first program means to operate the feeding and shearing and transport means to separate a predetermined volume of solder from a spool and deposit said volume in the crucible,

second program means for operating the laser energy means to first melt the predetermined volume of solder in the crucible and then to maintain the solder at a predetermined soldering temperature,

third program means to move the crucible vertically to a soldering position beneath a hole in the board, and

fourth program means to position the crucible downwardly from the soldering position to receive another piece of solder from the transport means.

6. A system according to claim 5 wherein the laser energy means is positioned to direct the beam along a path substantially coincident with the path of travel of the crucible into and out of soldering position.

7. A system according to claim 5 wherein the solder transport means comprises

a member operable to move in a path normal to the path of the crucible, said member having a vertical bore therein for accommodating a sheared piece of solder,

first means to apply air pressure radially in said bore to contain the solder piece in the bore while the solder piece is carried from the shearing means to the crucible,

second means to apply pressure vertically to assist gravity in depositing the solder piece in the crucible.

8. A system according to claim 5 wherein the second program means includes means operative to control the laser energy means to generate energy at one power level to melt the solder, and includes means to generate power at a second level to maintain the solder at a predetermined temperature to effect the soldering of the joint.