Method and apparatus for assembling multichip modules
First Claim
1. An apparatus for assembling a multichip module having an array of high density contact pads on a substrate and a matching array of contact pads on an unpackaged device, the apparatus comprising:
- a solder paste, and wherein said solder paste includesa) a solder,b) a removing agent for metal oxides,c) a low temperature component that substantially evaporates below or at said reflow temperature but does not substantially evaporate at room temperature,d) a high temperature component that evaporates slowly at the reflow temperature,e) a rheological modifier that allows said printing, andf) a flux mixture consisting of diphenic acid, propyl-4-hydroxy benzoate, ethyl cellulose, castor oil, rosin gum and poly-propylene glycol;
means for printing the solder paste selectively onto the contact pads of the substrate for forming a solder paste pattern;
means for positioning in opposed alignment and in contact the contact pads on the device and the solder paste that forms the pattern; and
means for heating the solder paste at a reflow temperature for forming solder joints between the contact pads on the substrate and the contact pads on the device.
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Accused Products
Abstract
A multichip module is assembled using flip-chip bonding technology, a stencil printable solder paste and standard surface mount equipment for interconnecting signaling input/output contact pads on devices within such a multichip module. The disclosed assembly process makes the heretofore difficult and expensive flip chip bonding technique achievable at low cost. The flip chip bonding technique is simplified by use of a solder paste which includes desirable reflow alignment, fluxing and printability characteristics. These desirable characteristics allow the assembly process to be further economically achieved by permitting the use of standard surface mount equipment in the process. High volume production of standard inexpensive modules are thus possible through this process while also achieving the advantage of high density interconnections afforded through the flip-chip bonding technology.
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Citations
19 Claims
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1. An apparatus for assembling a multichip module having an array of high density contact pads on a substrate and a matching array of contact pads on an unpackaged device, the apparatus comprising:
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a solder paste, and wherein said solder paste includes a) a solder, b) a removing agent for metal oxides, c) a low temperature component that substantially evaporates below or at said reflow temperature but does not substantially evaporate at room temperature, d) a high temperature component that evaporates slowly at the reflow temperature, e) a rheological modifier that allows said printing, and f) a flux mixture consisting of diphenic acid, propyl-4-hydroxy benzoate, ethyl cellulose, castor oil, rosin gum and poly-propylene glycol; means for printing the solder paste selectively onto the contact pads of the substrate for forming a solder paste pattern; means for positioning in opposed alignment and in contact the contact pads on the device and the solder paste that forms the pattern; and means for heating the solder paste at a reflow temperature for forming solder joints between the contact pads on the substrate and the contact pads on the device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for assembling a multichip module having an array of high density contact pads on a silicon substrate and a matching array of contact pads on an unpackaged integrated circuit chip, the apparatus comprising:
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means for printing with automated surface mount equipment a solder paste selectively onto the contact pads of the substrate to form a solder paste pattern, the solder paste comprising a solder, a removing agent for metal oxides, a low temperature component that substantially evaporates below or at said reflow temperature but does not substantially evaporate at room temperature, a high temperature component that evaporates slowly at the reflow temperature, and a rheological modifier that allows said printing; means for positioning said unpackaged integrated circuit chip with said automated surface mount equipment, by said positioning means, the contact pads on the unpackaged integrated circuit chip being positioned in opposed alignment and in contact with the solder paste that forms the solder paste pattern; and means for heating with said surface mount equipment the solder paste at a reflow temperature to form solder joints between the contact pads on the substrate and the contact pads on the unpackaged integrated circuit chip. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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Specification