Photopolymerizable compositions for encapsulating microelectronic devices

• US 6,099,783 A
• Filed: 08/07/1998
• Issued: 08/08/2000
• Est. Priority Date: 06/06/1995
• Status: Expired due to Term

• Current Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Original Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Inventors: Scranton, Alec B., Baikerikar, Kiran K., Rangarajan, Bharath
• Primary Examiner(s): Berman, Susan W.
• Application Number:
  US09/130,672
• Time in Patent Office: 732 Days
• Field of Search: 264/272.17, 264/272.11, 264/494, 264/496, 427/213.3, 427/512, 427/519, 522/64, 522/43, 522/81, 522/83, 522/13, 522/24, 522/170, 522/100, 522/103
• US Class Current: 264/272.11
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: B29C 2035/0838 using laser
• CPC Class Codes: B29C 35/0888 using transparant moulds
• CPC Class Codes: B29C 37/0067 Using separating agents during or after moulding; Applying separating agents on preforms or articles, e.g. to prevent sticking to each other separating agents B29C33/60
• CPC Class Codes: B29K 2105/0854 in the form of a non-woven mat
• CPC Class Codes: B29K 2105/16 Fillers
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: C08F 2/48 by ultraviolet or visible light

Abstract

A novel method for producing thick composite parts based upon photopolymerizable compositions is disclosed. Also disclosed are novel methods for encapsulation of microelectronic devices based upon novel photopolymerizable compositions. The constituents of the photopolymerizable mixture comprise a monomer or monomers capable of polymerizing by free radical or cationic mechanisms, and a photoinitiator system which possesses an absorbance characteristic which is effectively reduced, or self-eliminating, upon initiation of the polymerization reaction. Parts having thicknesses up to 2 cm and thicker for varying end use applications are made by photopolymerizing such compositions. In addition, using such compositions composite parts can be made using a reinforcement material such as a glass fiber mat present in an amount by weight of from about 5 to about 70%.

Claims

1. A method for encapsulating a microelectronic device, comprising:

(a) placing said microelectronic device into a mold having a cavity, a place for said microelectronic device within said cavity, and at least one side allowing light to penetrate into the cavity;

(b) filling said mold with a photopolymerizable composition comprising at least one monomer to be photopolymerized to a polymer, a photoinitiator having a self-eliminating absorbance, and a filler, wherein said monomer does not have unduly facile extractable hydrogens so as to adversely affect the Photopolymerization and said monomer and polymer have minimal absorbance in the wavelength range where polymerization is initiated;

(c) initiating polymerization of said photopolymerizable composition by exposing said composition in said mold to light in an ultraviolet wavelength range where photopolymerization is initiated, and such that the light penetrates into the cavity of said mold; and

(d) exposing said photopolymerizable composition to said light for a time adequate to cure said composition throughout.

2. The method of claim 1, wherein said monomer is an epoxy vinyl ester.

3. The method of claim 1, wherein said photoinitiator is benzoin ethyl ether.

4. The method of claim 3, wherein said benzoin ethyl ether is present in an amount of about 0.2 weight percent based upon the total weight of the photopolymerizable composition.

5. The method of claim 1, wherein said photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

6. The method of claim 5, wherein said bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is present in an amount of about 0.2 weight percent based upon the total weight of the photopolymerizable composition.

7. The method of claim 1, wherein said filler is powdered E-glass fibers or fused silica.

8. The method of claim 7, wherein said filler is present in an amount of about 50 to about 80 weight percent based upon the total weight of the photopolymerizable composition.

9. The method of claim 7, wherein said filler is present in an amount of about 60 weight percent based upon the total weight of the photopolymerizable composition.

10. The method of claim 7, wherein said filler is present in an amount of about 70 weight percent based upon the total weight of the photopolymerizable composition.

11. The method of claim 1, wherein the said ultraviolet wavelength range is about 320 to about 360 nm.

12. The method of claim 1, wherein the said microelectronic device is a semiconductor.

13. A method for encapsulating a microelectronic device, comprising:

(a) placing said microelectronic device into a mold having a cavity, a place for said microelectronic device within said cavity, and at least one side allowing light to penetrate into the cavity;

(b) filling said mold with a photopolymerizable composition comprising at least one monomer to be photopolymerized to a polymer, a photoinitiator having a self-eliminating absorbance, a thermal initiator, and a filler, wherein said monomer does not have unduly facile extractable hydrogens so as to adversely affect the photopolymerization and said monomer and polymer have minimal absorbance in the wavelength range where polymerization is initiated;

(c) initiating polymerization of said photopolymerizable composition by exposing said composition in said mold to light in an ultraviolet wavelength range where photopolymerization is initiated, and such that the light penetrates into the cavity of said mold; and

(d) exposing said photopolymerizable composition to said light for a time adequate to cure said composition throughout.

14. The method of claim 13, wherein said thermal initiator is benzoyl peroxide.

15. A method for encapsulating a microelectronic device, comprising:

(a) applying a photopolymerizable composition on said microelectronic device wherein said photopolymerizable composition comprises at least one monomer to be photopolymerized to a polymer, a photoinitiator having a self-eliminating absorbance, and a filler, wherein said monomer does not have unduly facile extractable hydrogens so as to adversely affect the photopolymerization and said monomer and polymer have minimal absorbance in the wavelength range where Polymerization is initiated;

(b) initiating polymerization of said photopolymerizable composition by exposing said composition to light in an ultraviolet range where photopolymerization is initiated; and

(c) exposing said photopolymerizable composition to said light for a time adequate to cure said composition.

16. The method of claim 15, wherein said monomer is an epoxy vinyl ester.

17. The method of claim 15, wherein said photoinitiator is benzoin ethyl ether.

18. The method of claim 17, wherein said benzoin ethyl ether is present in an amount of about 0.2 weight percent based upon the total weight of the photopolymerizable composition.

19. The method of claim 15, wherein said photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

20. The method of claim 19, wherein said bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is present in an amount of about 0.2 weight percent based upon the total weight of the photopolymerizable composition.

21. The method of claim 15, wherein said filler is powdered E-glass fibers or fused silica.

22. The method of claim 21, wherein said filler is present in an amount of about 50 to about 80 weight percent based upon the total weight of the photopolymerizable composition.

23. The method of claim 21, wherein said filler is present in an amount of about 60 weight percent based upon the total weight of the photopolymerizable composition.

24. The method of claim 21, wherein said filler is present in an amount of about 70 weight percent based upon the total weight of the photopolymerizable composition.

25. The method of claim 15, wherein the said ultraviolet wavelength range is about 320 to about 360 nm.

26. The method of claim 15, wherein the said microelectronic device is a semiconductor.

27. A method for encapsulating a microelectronic device, comprising:

(a) applying a photopolymerizable composition on said microelectronic device wherein said photopolymerizable composition comprises at least one monomer to be photopolymerized to a polymer, a photoinitiator having a self-eliminating absorbance, a thermal initiator, and a filler, wherein said monomer does not have unduly facile extractable hydrogens so as to adversely affect the photopolymerization and said monomer and polymer have minimal absorbance in the wavelength range where polymerization is initiated;

(b) initiating polymerization of said photopolymerizable composition by exposing said composition to light in an ultraviolet range where photopolymerization is initiated; and

(c) exposing said photopolymerizable composition to said light for a time adequate to cure said composition.

28. The method of claim 27, wherein said thermal initiator is benzoyl peroxide.