Polymer encapsulated electrical devices
View Patent ↗Improved encapsulated, overmolded and/or underfilled electrical components having a complete encapsulation, overmolding and/or underfilling with a coefficient of thermal expansion that is uniform and substantially free of gradients includes a polymeric matrix and an inorganic filler having a platelet geometric structure. The platelet structure of the filler allows a desirable coefficient of thermal expansion to be achieved using a very low level of filler material. This low level of filler material facilitates lower viscosity during forming of the encapsulation and/or overmolding, thereby facilitating complete filling of a mold cavity and underfilling of space between a circuit board and a semi-conductor chip electrically connected to the circuit board. In addition, the low viscosity has processing advantages that reduce the potential for damage to electrical components during encapsulation, overmolding and/or underfilling.
1. An overmolded electrical component, comprising:
a circuit board substrate having an electrical circuit;
a semi-conductor chip overlying the substrate and spaced apart therefrom by a distance of about 10 micrometers to about 150 micrometers, thereby creating a space between the circuit board substrate and the semi-conductor chip;
solder interconnections located within the space and connecting the electrical circuit to the semiconductor chip; and
a polymeric overmolding encapsulating the semi-conductor chip on the substrate and filling the space between the semi-conductor chip and the substrate about the solder interconnections, said polymeric overmolding being composed of a polymeric composite including a synthetic resin matrix and inorganic filler particles substantially uniformly distributed in the synthetic resin matrix, the inorganic filler particles having a platelet structure defined by opposite substantially flat and substantially parallel faces and being characterized by a dimensions between about 1 and 700 nanometers, the inorganic filler particle content being 20 percent or less by weight based on the weight of the polymeric composite.
2. The component of claim 1 , wherein the electrical component is a substrate having an electrical circuit formed on at least one surface of the substrate and at least one semi-conductor chip electrically connected to the electrical circuit.
3. The component of claim 1 , wherein the inorganic filler particle content is 15 percent or less by weight based on the weight of the polymeric composite.
4. The component of claim 1 , wherein the inorganic filler particle is a smectite clay mineral.
5. The component of claim 4 , wherein the smectite clay mineral is montmorillonite.
6. The component of claim 1 , wherein the synthetic resin matrix is a thermoset resin.
7. The component of claim 6 , wherein the thermoset resin is selected from epoxy, phenolic, polyurethane and polyurea resins.
8. The component of claim 1 , wherein the synthetic resin matrix is a thermoplastic resin.
9. The component of claim 8 , wherein the thermoplastic resin is selected from polyamides, copolyamides, polycarbonates, polyesters and copolyesters.
10. The component of claim 1 , wherein the polymeric composite has a CTE from about 5 to 20 ppm/° C.
11. An overmolded electrical component, comprising:
a substrate having an electrical circuit;
a semi-conductor chip electrically connected to the substrate, the semi-conductor chip being spaced from the substrate by a distance of from about 10 micrometers to about 150 micrometers; and
a polymeric overmolding encasing the component and formed of a polymeric composite, said polymeric overmolding filling said space defined between the semi-conductor chip and the substrate and overlying a surface of the component opposite the space;
wherein the polymer composite includes a synthetic resin matrix and inorganic filler particles substantially uniformly distributed in the synthetic resin matrix, the inorganic filler particles having a platelet structure defined by opposite substantially flat and substantially parallel faces and being characterized by a thickness between about 1 and 20 nanometers and a ratio of a surface area of a face to the thickness of at least 100, the inorganic filler particle content being 20% or less by weight based on the weight of the polymer composite.