Method and apparatus for improving the performance of light emitting diodes

• US 5,514,627 A
• Filed: 01/24/1994
• Issued: 05/07/1996
• Est. Priority Date: 01/24/1994
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.), Hewlett-Packard Company (HP Inc.), Sandia Corporation (Martin Marietta Corporation)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Martin, James, McElfresh, David K., Adolf, Douglas B., Burchet, Steve, Lowery, Christopher H.
• Primary Examiner(s): Picardat, Kevin M.
• Application Number:
  US08/186,196
• Time in Patent Office: 834 Days
• Field of Search: 437/209, 437/211, 437/214, 437/217, 437/219, 437/220, 437/215, 437/2, 437/3
• US Class Current: 438/26
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/32257 the layer connector connecting to a bonding area disposed in a recess of the surface of the item
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/56 Materials, e.g. epoxy or silicone resin
• CPC Class Codes: Y10S 438/938 Lattice strain control or utilization

Abstract

A method for increasing the resistance of a light emitting diode and other semiconductor devices to extremes of temperature is disclosed. During the manufacture of the light emitting diode, a liquid coating is applied to the light emitting die after the die has been placed in its lead frame. After the liquid coating has been placed on the die and its lead frames, a thermosetting encapsulant material is placed over the coating. The operation that cures the thermosetting material leaves the coating liquid intact. As the die and the encapsulant expand and contract at different rates with respect to changes in temperature, and as in known light emitting diodes the encapsulating material adheres to the die and lead frames, this liquid coating reduces the stresses that these different rates of expansion and contraction normally cause by eliminating the adherence of the encapsulating material to the die and frame.

Claims

1. A method for improving the performance of a light emitting diode, the light emitting diode comprising at least a light emitting die, a first and second lead frame and an encapsulation layer, the method comprising the step of placing a liquid coating over the die after the die has been placed and coupled to the first and second lead frames, the step of placing the liquid coating over the die and lead frames preceding the step of placing the encapsulation layer over the die, the liquid coating remaining liquid throughout the lifetime of the light emitting diode.

2. The method of claim 1 wherein the liquid coating comprises a non-conductive material which is immiscible in the encapsulating layer.

3. The method of claim 2 wherein the liquid coating comprises one of the group of polyalkylmethylsiloxane, dimethylpolysiloxane, and polyarylalkylsiloxanes.

4. A method for improving the reliability performance of a semiconductor device, the semiconductor device comprising at least one active semiconductor element, the active semiconductor element being coupled to at least a first and second electrical contact, the active semiconductor element and the first and second electrical contacts being mounted in a package comprising a thermosetting material, the method comprising the step of coating the active semiconductor element and the first and second electrical contacts with a liquid coating after the electrical contacts have been coupled to the active semiconductor element and before the active semiconductor element and the electrical contacts have been encapsulated in the thermosetting material, the liquid coating remaining liquid for the entire operational life of the semiconductor device.

5. The method of claim 4 wherein the liquid coating is immiscible in the thermosetting material.

6. The method of claim 5 wherein the liquid coating comprises a polyarylalkylsiloxane material.

7. The method of claim 5 wherein the liquid coating has a refractive index approximately the same as that of the thermosetting material.