Methods for mounting surface-mounted electrical components
View Patent ↗Methods for mounting electrical components on a substrate and securely retaining the components are described. The methods include altering solder paste compositions, interposed between component retentive pins and retentive through holes, during a reflow process. Electronic assemblies including circuit boards and electrical components mounted thereto are also described. In one of the electronic assembly embodiments, materials originally associated with a mounted electrical component migrate into solder paste coupling the electrical component to the circuit board.
1. A method for mounting and retaining an electrical component on a substrate that is subjected to at least two thermal cycles, the method comprising the steps of:
a) providing a substrate including a retentive through hole having a wall;
b) providing an electrical component having a retentive pin extending therefrom, said retentive pin having a diameter smaller than that of said retentive through hole;
c) disposing solder paste of a first solder composition into said retentive through hole;
d) inserting said retentive pin into said retentive through hole;
e) subjecting said substrate to a first thermal cycle such that material associated with at least one of said retentive through hole wall and said retentive pin migrates into said solder paste to create a mixed solder composition which has a higher melting point than that of said first solder composition; and
f) subjecting said substrate to a second thermal cycle having a peak temperature less than the melting point of said mixed solder composition, whereby said retentive pin remains securely held in said retentive through hole.
2. The method of claim 1 , wherein the migrated material was originally plating material disposed on said retentive pin.
3. The method of claim 2 , wherein the plating material comprises palladium.
4. The method of claim 2 , wherein the plating material comprises gold.
5. The method of claim 1 , wherein the migrated material was originally plating material disposed on said retentive through hole wall.
6. The method of claim 1 , wherein the migrated material includes plating material originally disposed on both of said retentive through hole wall and said retentive pin.
7. The method of claim 1 , wherein the migrated material is present in an amount of at least about 0.5% by weight at a solder location proximate said retentive through hole wall.