US3755890A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Vacuum-heat treatment of printed circuit boards
Assignee: Unisys Corp
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Filing: 1970-01-12
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Granted: 1973-09-04
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Expires: 1990-01-12
Abstract
Abstract Relates to the avoidance of electrical discontinuities arising in the production of two-sided printed circuit boards having plated-through-holes and particularly occurring in the use of solder for improving the electrical interconnections. Research disclosed that the cause of these discontinuities lay in the material of the boards surrounding the holes which either included entrapped gas or matter vaporizable under the high temperatures of the liquid solder applied to fill the holes and which impaired the attainment of reliable plated-through-hole connections. A vacuum evaporation operation is incorporated in the fabrication process and found highly useful and efficient in the production of reliable hole connections substantially reducing if not completely eliminating any need to apply solder touch-ups to the boards thereafter. Specifically, the boards are treated prior to the soldering of the plated-through holes to a temperature of approximately 250* F while concurrently being exposed to a vacuum of approximately 10 2 mm Hg for a sufficient time to drive out of the boards all matter vaporizable under such conditions. In carrying out this vacuum-heat treatment operation, inert gas is initially used in the treatment chamber to hasten the heating of the boards following which the chamber is exhausted of the gas and subjected to high vacuum while maintaining the temperature to which the boards have been raised. In returning the heat treatment chamber to normal room conditions, an inert gas may be re-introduced into the chamber to hasten the cooling of the circuit boards. When there will be an elapse of time before the soldering operation is performed, the de-gassed circuit boards are preferably placed in sealed containers or bags to prevent contact with the atmosphere and the resultant absorption of moisture and deleterious gasses therefrom.
Inventors
- 👤 W Klehm
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 05:18
CPC Classifications
H; H05; H05K; H05K3/00; H05K3/0011; H05K3/0055; H05K2201/00; H05K2201/09; H05K2201/09209; H05K2201/095; H05K2201/09572; H05K2203/00; H05K2203/08; H05K2203/083; H05K2203/085; H05K2203/11; H05K2203/1105; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49117; Y10T29/49124; Y10T29/49155
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
114 words
The method of outgassing printed circuit boards placed in a vacuum furnace which comprises the steps of loading the chamber of the furnace with a batch of printed circuit boards and sealing the same therewithin, replacing the air within the chamber by an inert gas, heating the chamber while the boards are in the presence of the inert gas up to a desired operating temperature above 212*F but below that which would detrimentally affect the material of the boards, and after the boards have reached the desired operating temperature exhausting the inert gas and vaporized material of the boards from the chamber by lowering the vacuum condition in the chamber to below one Torr.
Claim 2
Independent Claim
114 words
The method of outgassing printed circuit boards placed in a vacuum furnace which comprises the steps of loading the chamber of the furnace with a batch of printed circuit boards and sealing the same therewithin, replacing the air within the chamber by an inert gas, heating the chamber while the boards are in the presence of the inert gas up to a desired operating temperature above 212*F but below that which would detrimentally affect the material of the boards, and after the boards have reached the desired operating temperature exhausting the inert gas and vaporized material of the boards from the chamber by lowering the vacuum condition in the chamber to below one Torr.
Claim 3
Dependent Claim
33 words
The invention described in claim 1 characterized in that the chamber of the vacuum furnace is concurrently maintained at the desired operating temperature and the vacuum condition specified for at least three hours.
Claim 4
Dependent Claim
40 words
The invention described in claim 2 characterized in that immediately following the vacuum-heat treatment of the printed circuit boards and their removal from the vacuum furnace, the boards are hermetically sealed within an enclosure to avoid exposure to the atmosphere.
Claim 5
Dependent Claim
150 words
In the method of fabricating plastic composition boards which bear electrical conductors on opposite surfaces thereof and are electrically connected by plated-through-holes and which are subjected to a soldering operation filling the holes with molten solder, the steps of preparing such boards for the soldering operation which comprises enclosing the boards within an airtight chamber, replacing the air within the chamber with an inert gas, heating the chamber while the boards are in the presence of the inert gas up to a temperature no higher than that which would detrimentally affect the boards, exhausting the inert gas from the chamber without substantially reducing the temperature to which the chamber has been heated, continuing the exhaustion of the chamber to a vacuum condition below one Torr, and maintaining the chamber in such heated and high vacuum condition until substantially all material in the boards vaporizable under such condition are outgassed therefrom.
Claim 6
Dependent Claim
150 words
In the method of fabricating plastic composition boards which bear electrical conductors on opposite surfaces thereof and are electrically connected by plated-through-holes and which are subjected to a soldering operation filling the holes with molten solder, the steps of preparing such boards for the soldering operation which comprises enclosing the boards within an airtight chamber, replacing the air within the chamber with an inert gas, heating the chamber while the boards are in the presence of the inert gas up to a temperature no higher than that which would detrimentally affect the boards, exhausting the inert gas from the chamber without substantially reducing the temperature to which the chamber has been heated, continuing the exhaustion of the chamber to a vacuum condition below one Torr, and maintaining the chamber in such heated and high vacuum condition until substantially all material in the boards vaporizable under such condition are outgassed therefrom.
Claim 7
Dependent Claim
61 words
The invention described in claim 4 characterized in that the temperature to which the chamber is heated is approximately 250* F and that the vacuum therein is approximately 10 2 mm Hg and further characterized in that such temperature and vacuum levels in the chamber are maintained until substantially all material in the boards vaporizable under such conditions are outgassed therefrom.
Claim 8
Dependent Claim
137 words
In the method of making printed circuit boards wherein such boards are composed of a plastic composition and bear electrical conductors on opposite surfaces thereof connected by one or more holes extending through the boards and wherein molten solder is introduced into the holes formed therein, the steps of subjecting the boards to a vacuum evaporation treatment prioR to the introduction of solder into the holes which includes: subjecting the boards while in the presence of an inert gas to a temperature approaching but below that at which the material of the boards will be detrimentally affected thereby, and thereafter subjecting the boards to a vacuum pressure of at least one Torr while maintaining the same at approximately said temperature for driving out from the boards said inert gas and substantially all matter vaporizable under such conditions.
Claim 9
Dependent Claim
137 words
In the method of making printed circuit boards wherein such boards are composed of a plastic composition and bear electrical conductors on opposite surfaces thereof connected by one or more holes extending through the boards and wherein molten solder is introduced into the holes formed therein, the steps of subjecting the boards to a vacuum evaporation treatment prioR to the introduction of solder into the holes which includes: subjecting the boards while in the presence of an inert gas to a temperature approaching but below that at which the material of the boards will be detrimentally affected thereby, and thereafter subjecting the boards to a vacuum pressure of at least one Torr while maintaining the same at approximately said temperature for driving out from the boards said inert gas and substantially all matter vaporizable under such conditions.
Claim 10
Dependent Claim
33 words
The invention described in claim 6 characterized in that following such treatment of the boards they are returned to normal atmospheric pressure and temperature conditions while in the presence of an inert gas.
Claim 11
Dependent Claim
24 words
The invention described in claim 7 characterized in that following such treatment of the boards they are protectively sealed against exposure to the atmosphere.
Claim 12
Dependent Claim
135 words
In the method of manufacturing printed circuit boards wherein such boards are composed of a plastic composition and bear electrical conductors on surfaces thereof connected by plated-through-holes, the method of pretreating such hole plated boards prior to the application of solder to fill the holes therein comprising the steps of: sealing the boards within an airtight chamber containing an inert gas, heating the sealed chamber with the inert gas therewithin to a temperature above 212* F but below that at which the material of the boards would be detrimentally affected thereby, and lowering the pressure in the chamber while the chamber is so sealed and so heated to a vacuum pressure below one Torr for a time sufficient to drive out said inert gas and substantially all matter in the boards vaporizable under such conditions.
Claim 13
Dependent Claim
135 words
In the method of manufacturing printed circuit boards wherein such boards are composed of a plastic composition and bear electrical conductors on surfaces thereof connected by plated-through-holes, the method of pretreating such hole plated boards prior to the application of solder to fill the holes therein comprising the steps of: sealing the boards within an airtight chamber containing an inert gas, heating the sealed chamber with the inert gas therewithin to a temperature above 212* F but below that at which the material of the boards would be detrimentally affected thereby, and lowering the pressure in the chamber while the chamber is so sealed and so heated to a vacuum pressure below one Torr for a time sufficient to drive out said inert gas and substantially all matter in the boards vaporizable under such conditions.
Claim 14
Dependent Claim
43 words
The invention described in claim 9 characterized in that following such pretreatment of the boards the chamber is maintained sealed and an inert gas is admitted thereinto while the interior of the chamber is returned to approximately normal atmospheric temperature and pressure conditions.
Claim 15
Dependent Claim
36 words
The invention described in claim 10 characterized in that after the removal of the boards from the chamber following such pretreatment they are hermetically sealed within one or more enclosures each containing an inert gaseous medium.
Claim 16
Dependent Claim
125 words
In the method of manufacturing printed circuit boards wherein such boards are composed of a plastic composition and bear electrical conductors on surfaces thereof connected by plated-through-holes and wherein such boards are subjected to a vacuum evaporation treatment prior to the filling of the holes with molten solder during which treatment the boards are heated to a temperature above 212*F but below that at which material of the boards would be detrimentally affected thereby and concurrently subjected to a vacuum pressure below one Torr for a time sufficient to drive out substantially all vaporizable matter in the boards; the step of preventing the deleterious effects of the atmosphere on the boards following such treatment which comprises immediately hermetically sealing such treater boards within an enclosure.
Claim 17
Dependent Claim
125 words
In the method of manufacturing printed circuit boards wherein such boards are composed of a plastic composition and bear electrical conductors on surfaces thereof connected by plated-through-holes and wherein such boards are subjected to a vacuum evaporation treatment prior to the filling of the holes with molten solder during which treatment the boards are heated to a temperature above 212*F but below that at which material of the boards would be detrimentally affected thereby and concurrently subjected to a vacuum pressure below one Torr for a time sufficient to drive out substantially all vaporizable matter in the boards; the step of preventing the deleterious effects of the atmosphere on the boards following such treatment which comprises immediately hermetically sealing such treater boards within an enclosure.
Claim 18
Dependent Claim
22 words
The invention described in claim 12 wherein an inert gas is introduced into the enclosure before the boards are hermetically sealed therewithin.
Claim 19
Dependent Claim
154 words
In the method of making circuit boards wherein such boards are composed at least in part of a plastic composition and bear electrical conductors on opposite surfaces thereof connected by one or more holes extending through the boards and wherein molten metal is introduced into each of said holes to form an electrical connection between conductors on opposite surfaces of the boards, the steps of subjecting the boards to a vacuum evaporation treatment prior to the introduction of the molten metal into the holes which includes: subjecting the boards while in the presence of an inert gas to a temperature approaching but below that at which the material of the boards will be detrimentally affected thereby; and thereaFter subjecting the boards to a vacuum pressure below one Torr while maintaining the same at approximately said temperature for driving out from the boards said inert gas and substantially all matter therein vaporizable under such conditions.
Claim 20
Dependent Claim
154 words
In the method of making circuit boards wherein such boards are composed at least in part of a plastic composition and bear electrical conductors on opposite surfaces thereof connected by one or more holes extending through the boards and wherein molten metal is introduced into each of said holes to form an electrical connection between conductors on opposite surfaces of the boards, the steps of subjecting the boards to a vacuum evaporation treatment prior to the introduction of the molten metal into the holes which includes: subjecting the boards while in the presence of an inert gas to a temperature approaching but below that at which the material of the boards will be detrimentally affected thereby; and thereaFter subjecting the boards to a vacuum pressure below one Torr while maintaining the same at approximately said temperature for driving out from the boards said inert gas and substantially all matter therein vaporizable under such conditions.
Claim 21
Dependent Claim
151 words
In the method of manufacturing circuit boards wherein such boards are composed at least in part of a plastic composition and bear electrical conductors on opposite surfaces thereof connected by through-holes, the method of pre-treating such boards prior to the application of molten metal to fill the holes therein comprising the steps of: sealing the boards within an airtight chamber; heating the sealed chamber to a temperature above 212*F but below that at which the material of the boards would fuse; lowering the pressure in the chamber while the chamber is so sealed and so heated to a vacuum pressure below one Torr for a time sufficient to drive out substantially all matter in the boards vaporizable under such conditions; and introducing an inert gas into the chamber for absorption into the boards sealed therein while the interior of the chamber is returned to approximately normal atmospheric temperature and pressure conditions.
Claim 22
Dependent Claim
151 words
In the method of manufacturing circuit boards wherein such boards are composed at least in part of a plastic composition and bear electrical conductors on opposite surfaces thereof connected by through-holes, the method of pre-treating such boards prior to the application of molten metal to fill the holes therein comprising the steps of: sealing the boards within an airtight chamber; heating the sealed chamber to a temperature above 212*F but below that at which the material of the boards would fuse; lowering the pressure in the chamber while the chamber is so sealed and so heated to a vacuum pressure below one Torr for a time sufficient to drive out substantially all matter in the boards vaporizable under such conditions; and introducing an inert gas into the chamber for absorption into the boards sealed therein while the interior of the chamber is returned to approximately normal atmospheric temperature and pressure conditions.
Claim 23
Dependent Claim
34 words
The invention described in claim 15 wherein after the removal of the boards from the chamber following such pre-treatment, they are hermetically sealed within one or more enclosures each containing an inert gaseous medium.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-03 | 1977-03-05 | 1977-09-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-03 | 1981-03-05 | 1981-09-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-03 | 1985-03-05 | 1985-09-04 | $7700.00 | Window Closed / Lapsed |