SMT passive device noflow underfill methodology and structure
First Claim
1. A method of fabricating an electronic assembly, comprising:
- forming a mound of solder on each of at least a pair of electrical contacts on a substrate so as to form at least a pair of solder mounds;
applying a noflow resin encapsulant containing a flux material between said at least a pair of solder mounds so that said encapsulant partially covers said solder mounds;
pressing a passive SMD having at least a pair of electrical contacts into said resin encapsulant so that the said at least a pair of electrical contacts of said passive SMD respectively make contact with the said at least a pair of solder mounds; and
applying heat to said substrate and passive SMD so that initially said flux material is activated to prepare said electrical contacts for solder wetting and then said solder mounds melt and reflow to bond said electrical contacts and said resin encapsulant is cured.
4 Assignments
0 Petitions
Accused Products
Abstract
An electronic fabrication process and structure is provided for attaching discrete passive surface mount devices (SMD) to a substrate in a single step. A liquid noflow resin encapsulant containing flux material is dispensed between presoldered pads on a substrate. The SMD, having a pair of electrical contacts, is pressed into said encapsulant so that the electrical contacts make contact with said presoldered pads. Heat is applied to first activate said flux material and then reflow the solder on said presoldered pads to bond said SMD contacts to said presoldered pads. The reflow temperature is maintained for about 180 seconds during which time the resin solidifies. The resin encapsulant fills the space between substrate and SMD and forms fillets around the solder bonded contacts.
46 Citations
17 Claims
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1. A method of fabricating an electronic assembly, comprising:
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forming a mound of solder on each of at least a pair of electrical contacts on a substrate so as to form at least a pair of solder mounds;
applying a noflow resin encapsulant containing a flux material between said at least a pair of solder mounds so that said encapsulant partially covers said solder mounds;
pressing a passive SMD having at least a pair of electrical contacts into said resin encapsulant so that the said at least a pair of electrical contacts of said passive SMD respectively make contact with the said at least a pair of solder mounds; and
applying heat to said substrate and passive SMD so that initially said flux material is activated to prepare said electrical contacts for solder wetting and then said solder mounds melt and reflow to bond said electrical contacts and said resin encapsulant is cured. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of assembling an SMD on a substrate, comprising:
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forming a solder mound on each of at least a pair of electrical contacts on a substrate so as to form at least a pair of solder mounds;
dispensing a noflow liquid encapsulant including both flux material and resin underfill encapsulant onto said substrate in the space between said at least a pair of solder mounds in sufficient quantity so as to form a mound of encapsulant which partially covers said solder mounds;
pressing a passive SMD having at least a pair of electrical contacts into said mound of encapsulant so that respective ones of said at least a pair of electrical contacts of said passive SMD made contact with said at least a pair of solder mounds;
applying heat to said substrate and passive SMD so that said flux material is initially activated to prepare said electrical contacts for solder wetting; and
applying further heat to said substrate and passive SMD to melt and reflow said solder bumps so as to bond to said contacts and cause said resin encapsulant to form solid fillets around said SMD contacts and reflowed solder and fill the space between said SMD and substrate. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification