Method for selective encapsulation

• US 4,059,708 A
• Filed: 07/30/1976
• Issued: 11/22/1977
• Est. Priority Date: 07/30/1976
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Inventors: Heiss, John Herbert Jr., Schoen, Joel Mark
• Primary Examiner(s): Kendall, Ralph S.
• Application Number:
  US05/710,010
• Time in Patent Office: 480 Days
• Field of Search: 357/72, 427/259, 427/96, 427/273
• US Class Current: 427/96.2
• CPC Class Codes: H01L 21/32 using masks
• CPC Class Codes: H01L 21/56 Encapsulations, e.g. encapsulation layers, coatings
• CPC Class Codes: H01L 23/296 Organo-silicon compounds
• CPC Class Codes: H01L 23/3157 Partial encapsulation or coating mask layer used as insulation layer H01L21/31
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/19041 being a capacitor

Abstract

Disclosed is a method for encapsulating selected areas of solid state integrated circuits. The areas which are to remain uncoated are covered with a water and/or alcohol soluble polymer of sufficient viscosity to form stable droplets. The encapsulant is then applied, usually by flow coating, and cured. The polymer mask is removed by applying a material such as water or alcohol which does not affect the encapsulant. The method thus allows relatively small areas to be masked without any significant residue left on the circuit.

Claims

1. A method of selectively encapsulating a solid state integrated circuit formed on an insulating board comprising the steps of:

depositing on a selected area of the circuit a mask in the form of a stable droplet in a dome configuration with a height within the range 30-50 mils, said mask comprising a water soluble polymer which is inert to the organic solvents included in the encapsulant;

applying an encapsulating material comprising a room temperature vulcanizing silicone rubber dissolved in an organic solvent to said circuit by flow coating the material over the area of the circuit not covered by said mask;

curing said encapsulating material; and

dissolving said polymer material by applying water thereto so as to expose the area of the circuit covered by said polymer and leave encapsulating material on the remaining area of the circuit.

2. The method according to claim 1 wherein the polymer material is selected from the group consisting of polyvinyl alcohol, polyvinylpyrrolidone, hydroxypropyl cellulose, polyethylene oxide, polyacrylic acid, carboxy methyl cellulose, and gelatin.

3. The method according to claim 1 wherein the encapsulating material comprises a dimethyl siloxane long chain polymer with methoxy end groups dissovled in xylene.

4. The method according to claim 1 wherein the polymer material comprises mannitol-mannite and potato dextrin dissolved in a glycerin base.

5. The method according to claim 1 wherein the encapsulating material is cured by keeping the circuit at room temperature and at a relative humidity between 30 and 60% followed by heating the circuit at a temperature in the range 90°

-140°

C for a period of time in the range 2-6 hours.