Soldering method capable of providing a joint of reduced thermal resistance
First Claim
1. A method of soldering two members together, which comprises:
- (a) placing a body of solder together with a flux between the two members;
(b) heating the solder and the flux to a prescribed temperature above the melting point of the solder and above a flux activation temperature at which the flux generates a gas;
(c) maintaining the solder and the flux at the prescribed temperature for a preassigned length of time; and
(d) exerting a compressive force on the solder through at least either of the two members in order to drive off the gas bubbles generated by the flux from the molten body of solder and hence to provide a joint of reduced thermal resistance.
1 Assignment
0 Petitions
Accused Products
Abstract
A soldering method is disclosed as adapted for attaching semiconductor devices such as transistors to their lead mounts. A layer of a solder paste, premixed with rosin flux, is first printed or otherwise formed on each of a series of interconnected semiconductor mounts which may be in the form of a sheet metal punching. The semiconductor devices are placed on the respective solder layers. Then the solder layers are heated to a prescribed temperature higher than both the melting point of the solder and a flux activation temperature at which the flux starts bubbling within the solder. For thus heating the solder layers, the series of semiconductor mounts with the semiconductor devices placed thereon via the solder layers may be fed longitudinally over a suitably heated surface. Upon lapse of a preassigned length of time following the activation of the flux, a compressive is exerted on the successive solder layers, thereby driving of the gas bubbles generated by the flux for the provision of joints of reduced thermal resistance.
19 Citations
15 Claims
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1. A method of soldering two members together, which comprises:
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(a) placing a body of solder together with a flux between the two members; (b) heating the solder and the flux to a prescribed temperature above the melting point of the solder and above a flux activation temperature at which the flux generates a gas; (c) maintaining the solder and the flux at the prescribed temperature for a preassigned length of time; and (d) exerting a compressive force on the solder through at least either of the two members in order to drive off the gas bubbles generated by the flux from the molten body of solder and hence to provide a joint of reduced thermal resistance.
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2. A method of soldering two members together, which comprises:
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(a) placing a body of solder together with a flux between the two members; (b) heating the solder and the flux to a prescribed temperature above the melting point of the solder and above a flux activation temperature at which the flux generates a gas; (c) maintaining the solder and the flux at the prescribed temperature for a preassigned length of time, with the solder held only under the weight of one of the two members in order to avoid a decrease in the thickness of the molten body of solder and hence to expedite the escape of the gas bubbles generated by the flux from the molten body of solder; and (d) exerting a compressive force on the solder through at least one of the two members in order to drive off the remaining gas bubbles from the molten body of solder and to reduce the thickness of the solder body, with a view to the provision of a soldered joint of reduced thermal resistance. - View Dependent Claims (3, 4, 5)
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6. A method of soldering two members together, which comprises:
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(a) placing a body of solder together with a flux between the two members; (b) heating the solder and the flux to a prescribed temperature above the melting point of the solder and above a flux activation temperature at which the flux generates a gas; (c) maintaining the solder and the flux at the prescribed temperature for a preassigned length of time, with the solder held only under the weight of one of the two members in order to avoid a decrease in the thickness of the molten body of solder and hence to expedite the escape of the gas bubbles generated by the flux from the molten body of solder; (d) exerting a compressive force on the solder through at least one of the two members during a preassigned part of the preassigned length of time when the solder is maintained at the prescribed temperature, in order to drive off the remaining gas bubbles from the molten body of solder and to reduce the thickness of the solder body; (e) releasing the compressive force from the solder before expiration of the preassigned length of time in order to allow the molten body of solder to re-increase in thickness; and (f) re-exerting a compressive force on the solder through at least one of the two members when the solder is in a molten state, in order to additionally drive off the remaining gas bubbles from the molten body of solder and to reduce the thickness of the solder body again, with a view to the provision of a soldered joint of reduced thermal resistance. - View Dependent Claims (7, 8, 9)
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10. A method of soldering semiconductor devices to their mounts, which comprises:
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(a) providing a series of interconnected semiconductor mounts having solderable surfaces; (b) forming layers of a solder paste on the solderable surfaces of the semiconductor mounts, the solder paste containing a flux; (c) placing the semiconductor devices on the solder paste layers; (d) heating the solder paste layers to a prescribed temperature above the melting point of the solder paste and above a flux activation temperature at which the flux generates a gas, by feeding the series of semiconductor mounts, together with the semiconductor devices placed thereon via the solder paste layers, longitudinally over a heating apparatus; and (e) exerting a compressive force on the successive solder paste layers via the semiconductor devices thereon while the solder paste layers are in a molten state, thereby driving off the gas bubbles generated by the flux from the solder paste layers and hence to provide joints of reduced thermal resistance between the semiconductor devices and their mounts. - View Dependent Claims (11, 12, 13, 14, 15)
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Specification