US4998342A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of attaching electronic components
Assignee: International Business Machines Corp
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Filing: 1989-08-31
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Granted: 1991-03-12
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Expires: 2009-08-31
Abstract
Abstract An improved method for double sided attachment of components to a printed circuit board is described wherein surface mount components soldered to a first surface of the circuit board (backside) are, once the board is inverted during reflow, retained in place only by force of molten solder surface tension.
Inventors
- 👤 Ralph E. Bonnell
- 👤 George C. Castello
- 👤 Karl G. Hoebener
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 22:04
CPC Classifications
H; H05; H05K; H05K13/00; H05K13/04; H05K13/046; H05K13/0469; H05K3/00; H05K3/30; H05K3/32; H05K3/34; H05K3/341; H05K3/3415; H05K2203/00; H05K2203/14; H05K2203/1476; H05K2203/15; H05K2203/1572; H05K3/303; H05K3/305; H05K3/3447; Y; Y02; Y02P; Y02P70/00; Y02P70/50; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49117; Y10T29/49124; Y10T29/4913; Y10T29/49144
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
94 words
A process for populating both sides of a printed circuit board comprising the sequential steps of: (a) screening solder onto surface mount lands on a first side of the printed circuit board; (b) placing surface mount components on said lands on said first side; (c) reflowing solder applied in step (a); (d) screening solder on surface mount lands and into plated through-holes on a second side of said printed circuit board; (e) placing surface mount and pin in hole components on said second side; and (f) reflowing all solder on said printed circuit board.
Claim 2
Dependent Claim
94 words
A process for populating both sides of a printed circuit board comprising the sequential steps of: (a) screening solder onto surface mount lands on a first side of the printed circuit board; (b) placing surface mount components on said lands on said first side; (c) reflowing solder applied in step (a); (d) screening solder on surface mount lands and into plated through-holes on a second side of said printed circuit board; (e) placing surface mount and pin in hole components on said second side; and (f) reflowing all solder on said printed circuit board.
Claim 3
Dependent Claim
42 words
The process of claim 1 including the additional step between steps (a) and (b) of: applying adhesive at sites on said first side of said printed circuit board for components having weight to lead ratio in excess of 0.1 grams per lead.
Claim 4
Dependent Claim
50 words
The process of claim 1 wherein step (b) includes choosing components having a weight to lead ratio less than or equal 0.1 grams per lead and said step (f) reflowing includes maintaining vibration level to which said printed circuit board is subjected less than or equal 2.54 cm per second.
Claim 5
Dependent Claim
22 words
The process of claims 1, 2 or 3 wherein step (f) includes passing the printed circuit board through an infrared reflow oven.
Claim 6
Dependent Claim
30 words
The process of claims 1, 2 or 3 wherein step (a) screening includes screening solder paste comprising at least 90% metal by weight, said metal being 63% tin, 37% lead.
Claim 7
Dependent Claim
119 words
An improved method of back side attach of surface mount components to a printed circuit substrate comprising these sequential steps of: (a) screening solder paste consisting of at least 90% metal by weight onto back side surface mount lands on the printed circuit board; (b) placing surface mount components on surface mount lands soldered in step (a); (c) reflowing solder paste; (d) inverting the printed circuit board; (e) populating the front side of said printed circuit board; and (f) reflowing all solder on said printed circuit board by passing said printed circuit board through an infrared convection oven while maintaining at a level less than or equal 2.54 cm per second Z axis displacement of said surface mount components.
Claim 8
Dependent Claim
119 words
An improved method of back side attach of surface mount components to a printed circuit substrate comprising these sequential steps of: (a) screening solder paste consisting of at least 90% metal by weight onto back side surface mount lands on the printed circuit board; (b) placing surface mount components on surface mount lands soldered in step (a); (c) reflowing solder paste; (d) inverting the printed circuit board; (e) populating the front side of said printed circuit board; and (f) reflowing all solder on said printed circuit board by passing said printed circuit board through an infrared convection oven while maintaining at a level less than or equal 2.54 cm per second Z axis displacement of said surface mount components.
Claim 9
Dependent Claim
27 words
The method of claim 6 wherein step (b) includes: choosing surface mount components having a weight to lead ratio less than or equal 0.1 gram per lead.
Claim 10
Dependent Claim
31 words
The process of claim 1 wherein step (1) includes: choosing a solder composition having in its molten state surface tension in the range of from about 450 to about 550 dynes/cm.
Claim 11
Dependent Claim
21 words
The method of claim 6 wherein step (a) includes: selecting a solder, said metal comprising a 63% tin, 37% lead alloy.
Claim 12
Dependent Claim
31 words
The method of claim 6 wherein step (a) includes: choosing a solder composition having in its molten state surface tension in the range of from about 450 to about 500 dynes/cm.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-03-11 | 1994-09-10 | 1995-03-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-03-11 | 1998-09-10 | 1999-03-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-03-11 | 2002-09-10 | 2003-03-12 | $7700.00 | Window Closed / Lapsed |