US5492266A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fine pitch solder deposits on printed circuit board process and product
Assignee: International Business Machines Corp
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Filing: 1994-08-31
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Granted: 1996-02-20
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Expires: 2014-08-31
Abstract
Abstract A method, and product created thereby, by which low melting point solder suitable for reflow connection of components is formed on select contacts of a printed circuit board. The method is particularly suited to the fabrication of populated printed circuit board having fine pitch devices including flip-chip devices, connected on a board including conventional coarse pitch surface mounted components. The fine pitch contacts of the board are exposed through holes in a stencil characterized in its ability to withstand solder reflow temperatures, not be wettable by solder, and have a coefficient of thermal expansion relatively matching the printed circuit board. Low temperature solder paste is screen deposited into the stencil openings. With the stencil fixedly positioned on the board, the solder paste retained by the stencil pattern is reflowed to selectively form on the underlying contacts of the printed circuit board. Thereafter, according to a preferred practice of the invention, the stencil is removed from the board and the board is subject to previously practiced depositions of flux and paste in preparation for fine and coarse pitch component placement and ensuing solder reflow. Alternate practices of the invention involve concurrent deposition of fine and coarse pitch solder and retention of the stencil following fine pitch solder fellow.
Inventors
- 👤 Karl G. Hoebener
- 👤 Eric M. Hubacher
- 👤 Julian P. Partridge
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:47
CPC Classifications
H; H05; H05K; H05K3/00; H05K3/30; H05K3/32; H05K3/34; H05K3/3465; H05K3/3485; B; B23; B23K; B23K3/00; B23K3/06; H05K3/10; H05K3/12; H05K3/1216; H05K3/1225; H10; H10W; H10W70/00; H10W70/099; B23K2101/00; B23K2101/36; H05K2201/00; H05K2201/09; H05K2201/09209; H05K2201/09654; H05K2201/09727; H05K2201/10; H05K2201/10613; H05K2201/10621; H05K2201/10674; H05K2203/00; H05K2203/04; H05K2203/043; H05K2203/0485; H05K2203/05; H05K2203/0548; H05K2203/0557; H05K2203/14; H05K2203/1476; H10W72/00; H10W72/01; H10W72/012; H10W72/01221; H10W72/01223; H10W72/01225; H10W72/01251; H10W72/01255; H10W72/071; H10W72/072; H10W72/07211; H10W72/07231; H10W72/07236; H10W72/20; H10W72/251; H10W72/252
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
82 words
A method of forming fine pitch solder deposits on a circuit board, comprising the steps of: positioning a metallic fine pitch stencil over the circuit board with openings aligned to select circuit board fine pitch contacts; screen depositing solder paste into openings of the positioned stencil; reflowing the solder paste while holding the positioned stencil against the circuit board to form solder on the select circuit board contacts; and releasing the stencil without removing the solder on the select circuit board contacts.
Claim 2
Independent Claim
82 words
A method of forming fine pitch solder deposits on a circuit board, comprising the steps of: positioning a metallic fine pitch stencil over the circuit board with openings aligned to select circuit board fine pitch contacts; screen depositing solder paste into openings of the positioned stencil; reflowing the solder paste while holding the positioned stencil against the circuit board to form solder on the select circuit board contacts; and releasing the stencil without removing the solder on the select circuit board contacts.
Claim 3
Dependent Claim
24 words
The method recited in claim 1, comprising the further step of: reflowing the solder on the select circuit board contacts to connect placed components.
Claim 4
Dependent Claim
18 words
The method recited in claim 1, wherein the stencil is formed from a material not wettable by solder.
Claim 5
Dependent Claim
18 words
The method recited in claim 2, wherein the stencil is formed from a material not wettable by solder.
Claim 6
Dependent Claim
28 words
The method recited in claim 1, wherein the stencil has tapered openings and is characterized by a coefficient of thermal expansion similar to that of the circuit board.
Claim 7
Dependent Claim
28 words
The method recited in claim 2, wherein the stencil has tapered openings and is characterized by a coefficient of thermal expansion similar to that of the circuit board.
Claim 8
Dependent Claim
31 words
The method recited in claim 2, comprising the further step of: screen depositing solder paste through a coarse pitched stencil for select components, before performing the step of reflowing the solder.
Claim 9
Dependent Claim
25 words
The method recited in claim 2, comprising the further step of: selectively depositing flux to hold components, before performing the step of reflowing the solder.
Claim 10
Dependent Claim
13 words
The method recited in claim 2, wherein the placed components are flip-chip die.
Claim 11
Independent Claim
109 words
A method of attaching fine pitch terminal components to a printed circuit board, comprising the steps of: placing a metallic non-wetting fine pitch stencil over the circuit board with openings aligned to select circuit board contacts; screen depositing a solder paste into the openings of the placed stencil; reflowing the solder paste while holding the placed stencil against the circuit board to form solder on the select board contacts; releasing the stencil without removing the solder on the select circuit board contacts; depositing flux on the solder over the select circuit board contacts; placing components; and reflowing the solder on the select circuit board contacts to connect placed components.
Claim 12
Independent Claim
109 words
A method of attaching fine pitch terminal components to a printed circuit board, comprising the steps of: placing a metallic non-wetting fine pitch stencil over the circuit board with openings aligned to select circuit board contacts; screen depositing a solder paste into the openings of the placed stencil; reflowing the solder paste while holding the placed stencil against the circuit board to form solder on the select board contacts; releasing the stencil without removing the solder on the select circuit board contacts; depositing flux on the solder over the select circuit board contacts; placing components; and reflowing the solder on the select circuit board contacts to connect placed components.
Claim 13
Dependent Claim
31 words
The method recited in claim 10, comprising the further step of: screen depositing solder paste through a coarse pitch stencil for select components, before performing the step of reflowing the solder.
Claim 14
Dependent Claim
29 words
The method recited in claim 10, wherein step of placing components comprises the placing of component terminals into the deposited flux before performing the step of reflowing the solder.
Claim 15
Dependent Claim
12 words
The method recited claim 10, wherein the placed components are flip-chip die.
References Cited (Backward Citations)
JPS5586679A
Cited
DE3608101A1
Cited
US4722470A
Cited
JPH03241889A
Cited
US5060844A
Cited
US5147084A
Cited
US5400953A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-02-19 | 1999-08-21 | 2000-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-02-19 | 2003-08-21 | 2004-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-02-19 | 2007-08-21 | 2008-02-20 | $7700.00 | Window Closed / Lapsed |