Non-precious metal furnace with inert gas firing

• US 4,767,104 A
• Filed: 04/02/1987
• Issued: 08/30/1988
• Est. Priority Date: 11/06/1985
• Status: Expired due to Fees

• Current Assignee: Honeywell Bull Incorporated
• Original Assignee: Honeywell Bull Incorporated
• Inventors: Plesinger, Boris
• Primary Examiner(s): Sheehan, John P.
• Assistant Examiner(s): KASTLER, SCOTT R
• Application Number:
  US07/033,869
• Time in Patent Office: 516 Days
• Field of Search: 266/144, 266/252, 266/108, 266/255, 266/257, 266/159, 75/5, 432/206, 432/200, 432/171, 432/164, 432/166
• US Class Current: 266/144
• CPC Class Codes: F27B 9/3077 Arrangements for treating electronic components, e.g. semiconductors
• CPC Class Codes: H05K 3/12 using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns

Abstract

A furnace for firing a non-precious metal paste including organic material, comprising a furnace enclosure, tube-like in shape, having a definable length. First and second ends of the furnace enclosure is open forming an entrance and exit, respectively. A cross-section across the length of the furnace enclosure has a flat base, a first and second vertical wall at each end of the flat base, and a roof, the shape of the roof being essentially the upper half of an ellipse. The interior chamber of the furnace is divided across the length of the furnace enclosure into a burnout zone and a firing zone, the entrance leading to the burnout zone, and the exit being nearest the firing zone. A sparging element distributes a mixture of an inert gas and at least one other gas within the burnout zone, wherein the other gas supports burnout of the organic material. A distributing element inserts an inert gas in the firing zone in the interior chamber of the furnace such that the non-precious metal is sintered in an inert atmosphere. A barrier element, providing a barrier such that the gas mixture of the burnout zone and the inert gas and the firing zone, are separated, thereby dividing the interior chamber of the furnace into the burnout zone and the firing zone. An exhaust means in the burnout zone where most smoke is produced as a result of the burnout of the organic material.

Claims

1. A furnace for firing substrates on which substrates have been placed a paste, said paste including a non-precious metal and an organic material, said furnace comprising:

a tube shaped furnace enclosure having a definable length and a pair of ends, the interior of the enclosure forming a chamber;

means forming in one end of the enclosure an entrance into the chamber, and means forming in the other end of the enclosure an exit from the chamber, said chamber being defined by a substantially horizontal base wall, first and second substantially vertical side walls and wall means connecting the first and second side walls and forming a roof of the chamber;

means forming a center barrier dividing the chamber into a first zone and a second zone, the first zone being in communication with the entrance to the chamber and the second zone being in communication with the exit, said means forming a center barrier preventing gases from the first zone substantially from entering the second zone;

means for sparging a mixture of an inert gas and oxygen within the burn-out zone, the oxygen supporting first of the organic material of the paste and further wherein said means for sparging provides uniform coverage of the substrates with the mixture of the inert gas and oxygen to reduce disruptive gas flow within the first zone;

means for inserting an inert gas in the second zone in the chamber so that the non-precious metal of the paste is sintered in an inert atmosphere;

first exhaust means being placed in the roof of the furnace in an area of the first zone in which most of the smoke is produced as a result of the burn-out of organic material, for removing said smoke from the first zone;

means for preventing ambient atmosphere from entering the chamber through the entrance, and means for preventing ambient atmosphere from entering the chamber through the exit;

second exhaust means for removing gases from said first zone proximate the means forming a center barrier; and

third exhaust means for removing gases from the second zone located proximate the means forming a center barrier.

2. A furnace as defined in claim 1 in which a cross section of the roof perpendicular to the length of the furnace being substantially half of an ellipse.

3. A furnace for firing substances on which substrates have been placed a paste, said paste including a powdered non-precious metal and an organic binder material, said furnace comprising:

a tube shaped furnace enclosure having a definable length and a pair of ends, the interior of the enclosure forming a chamber;

means forming in one end of the enclosure an entrance into the chamber, and means forming in the other end of the enclosure an exit from the chamber, said chamber being defined by a plurality of substantially planar walls, said walls including a substantially horizontal base wall, first and second substantially vertical side walls and a plurality of interconnecting walls forming a roof, said interconnecting walls interconnecting the first and second side walls and being positioned so as to be substantially tangential to the periphery of a cylindrical ellipsoid;

means forming a center barrier dividing the chamber into a first zone and a second zone, the first zone being in communication with the entrance to the chamber and the second zone being in communication with the exit, said means forming a center barrier forming an inert gas curtain between the first zone and the second zone so that gases from the first zone substantially are prevented from entering the second zone;

means for sparging a mixture of an inert gas and oxygen within the first zone, the oxygen supporting burn-out of the organic material of the paste and further wherein said means for sparging provides uniform coverage of the substrates with the mixture of the inert gas and oxygen to reduce distruptive gas flow within the burn-out zone;

means for inserting an inert gas in the second zone in the chamber so that the non-precious metal of the paste is sintered in an inert atmosphere;

first exhaust means being placed in the roof of the furnace in an area of the first zone in which most of the smoke is produced as a result of the burn-out of organic material, for removing said smoke from the first zone;

an inert gas curtain for preventing ambient atmosphere from entering the chamber through the entrance and an inert gas curtain for preventing ambient atmosphere from entering the chamber through the exit;

second exhaust means for removing gases from said first zone proximate the means forming a center barrier; and

third exhaust means for removing gases from the second zone located proximate the means forming a center barrier.

4. A furnace for firing ceramic substrates on which substrates have been placed a thick film paste, said paste including powdered copper and an organic binder material, said furnace comprising:

a tube shaped furnace enclosure having a definable length and a pair of ends, the interior of the enclosure forming a chamber;

means forming in one end of the enclosure an entrance into the chamber, and means forming in the other end of the enclosure an exit from the chamber, said chamber being defined by a plurality of substantially planar walls, said walls including a substantially horizontal base wall, first and second substantially vertical side walls, a substantially horizontal top wall, and two sets of connecting walls each set of connecting walls including a first connecting wall and a second connecting wall, each set of connecting walls connecting a side wall to the top wall, the angle between the top wall and the first connecting wall of each set connected to the top wall defining an angle of substantially 221/2° and

the second connecting wall of each set connecting a side wall and a first connecting wall of each set defining an angle of substantially 45°

with respect to the horizontal;

means for preventing ambient atmosphere from entering the chamber;

means forming a center barrier dividing the chamber into a burn-out zone and a firing and cooling zone, the burn-out zone being in communication with the entrance to the chamber and the firing and cooling zone being in communication with the exit, said means forming a center barrier forming a nitrogen curtain between the burn-out zone and the firing zone so that gases from the burn-out zone substantially are prevented from entering the firing and cooling zone;

means for sparging a mixture of nitrogen and oxygen within the burn-out zone, the oxygen supporting burn-out of the organic material of the paste and further wherein said means for sparging provides uniform coverage of the substrates with the mixture of the nitrogen and oxygen to reduce distruptive gas flow within the burn-out zone;

means for inserting nitrogen in the firing zone in the chamber so that the copper of the paste is sintered in an inert atmosphere;

first exhaust means being mounted in the top wall in an area of the burn-out zone in which most of the smoke is produced as a result of the burn-out of the organic material, for removing said smoke from the burn-out zone;

second exhaust means mounted in the top wall in the burnout zone near said means forming a center barrier for removing gases from the burn-out zone; and

third exhaust means mounted in the top wall in the firing and cooling zone near said means forming a center barrier for removing gases from the firing and cooling zone.