Process For Fabricating Electronic Components Using Liquid Injection Molding

Abstract

A process for fabricating an electronic component includes a liquid injection molding method for overmolding a semiconductor device. The liquid injection molding method includes: i) placing the semiconductor device in an open mold, ii) closing the mold to form a mold cavity, iii) heating the mold cavity, iv) injection molding a curable liquid into the mold cavity to overmold the semiconductor device, v) opening the mold and removing the product of step iv), and optionally vi) post-curing the product of step v). The semiconductor device may have an integrated circuit attached to a substrate through a die attach adhesive.

Description

EXAMPLES

These examples illustrate the invention to one skilled in the art and are not intended to limit the scope of the invention set forth in the claims.

Reference Example 1

Injection Molding Equipment

An Engel Silicone Liquid Injection Molding Machine (M/N: CC-90), which can operate between 1 and 90 tonnes clamping pressure with a 28 mm screw diameter is used for injection molding. This and comparable equipment are commercially available from ENGEL Machinery Inc., 3740 Board Road, Rd. #5, York, Pa., U.S.A.

Reference Example 2

Injection Molding Equipment

An Arburg Silicone Liquid Injection Molding Machine (M/N: ALLROUNDER 270S 250-60), which can operate between 1 and 27 tonnes clamping pressure with a 18 mm screw diameter is used for injection molding. This equipment is commercially available from ARBURG, Inc., 125 Rockwell Road, Newington, Conn. 06111, U.S.A.

Reference Example 3

Mold

A standard mold base (Catalogue: 812A-13-13-2) manufactured with Number #2 steel from D-M-E Co., 29111 Stephenson Highway, Madison Heights, Mich. 48071, USA is fabricated by Kipe Molds, Inc., 340 East Crowther Avenue, Placentia, Calif. 92870, U.S.A. to accommodate 1×6 array package. The mold is designed as a hot runner system.

Reference Example 4

1×6 BGA Strip

An electronics BGA strip with a 1×6 array strip and the following dimensions is fabricated: Length=187.5 mm, Width=40.0 mm, Height=either 0.36 mm or 0.61 mm.

Examples 1-3

Samples 1-3 are evaluated with the equipment in Reference Example 2, the mold in Reference Example 3, and the BGA strip in Reference Example 4. The samples are cured in the mold between 10-27 tonnes clamping pressure, with curing times of 30-240 sec at a temperature of 120° C. The results are in Table 1.

TABLE 1
Sample	Processability, Injection	Adhesion
1	YES	POOR
2	YES	GOOD
3	YES	POOR

Sample 1 is a resinous silicone matrix, which cures via hydrosilation. It forms an optically clear material upon cure. Sample 1 is a combination of 97 parts by weight of Resin/Crosslinker A and 3 parts by weight Catalyst/Inhibitor A. Resin/Crosslinker A is a combination of 81 parts vinyl-terminated silsesquioxane resin, 17 parts 1,4-bis(dimethylsilyl)benzene, 1 part of a reaction product of hydroxy-terminated dimethyl,methylvinylsiloxane, with (glycidoxypropyl)trimethoxysilane, and 1 part product(s) from the reaction of ethylene glycol and tetraethylorthosilicate. Catalyst/Inhibitor A is a combination of 3.6 parts divinyltetramethyldisiloxane and triphenylphosphine platinum complexes, 93.3 parts toluene, 3.0 parts triphenylphosphine, and 0.1 part tetramethyldivinyldisiloxane.

Sample 2 is a commercially available addition reaction curable liquid silicone composition; DOW CORNING® 6820 Microelectronic Encapsulant, which is commercially available from Dow Corning Corporation of Midland, Mich., U.S.A.

Sample 3 is a combination of 40 parts of the composition in sample 1 and 60 parts of fused silica.

Samples 1-3 show that different liquid silicone compositions are suitable for the liquid injection molding process. Sample 2 shows that adhesion can be obtained. cl DRAWINGS

FIG. 1 is a schematic representation of liquid injection molding process equipment for use in the method of this invention.

FIG. 2 a is a cross sectional view taken along line 108 of a mold 106 for use in the liquid injection molding process equipment 100 in FIG. 1. FIG. 2a shows the mold 106 in its open position. FIG. 2b is the mold 106 shown in its closed position.

FIG. 3 a is a cross sectional view taken along line 108 of an alternative mold 106 for use in the liquid injection molding process equipment 100 in FIG. 1. FIG. 3a shows the mold in its open position. FIG. 3b is the mold 106 in its closed position.

FIG. 4 a is a cross sectional view taken along line 108 of an alternative mold 106 for use in the liquid injection molding process equipment 100 in FIG. 1. FIG. 4a shows the mold in its open position. FIG. 4b shows the mold 106 in the closed position.

FIG. 5 is a cross sectional view taken along line 109 of a mold 106 according to FIG. 1.

FIG. 6 shows a cross sectional view taken along line 109 of a mold 106 according to FIG. 1.

FIG. 7 shows an electronic component 700 fabricated by the process of this invention.

FIG. 8 shows an alternative electronic component made by the process of this invention.

FIG. 9 shows an alternative electronic component 900 fabricated by the process of this invention.

REFERENCE NUMERALS

• 100 liquid injection molding process 109 cross section line
• 101 feed system 201 first section
• 102 feed tank 202 second section
• 103 feed tank 203 mold retainer
• 104 static mixer 204 substrate
• 105 extruder 205 semiconductor dice
• 106 mold 206 mold cavities
• 107 inlet 210 sprue
• 108 cross section line 211 runner system
• first section 902 wires
• mold retainer 903 integrated circuit
• substrate 904 die attach adhesive
• semiconductor dice 905 circuit board
• mold cavities 906 solder balls
• gates 910 encapsulant
• sprue
• runner system
• first section
• mold retainer
• substrate
• semiconductor dice
• mold cavities
• gates
• sprue
• runners
• electronic component
• overmold
• wires
• integrated circuit
• die attach adhesive
• circuit board
• solder balls
• electronic component
• overmold
• electrically conductive materials
• integrated circuit
• die attach adhesive
• circuit board
• solder balls
• electronic component
• overmold

Claims

1. A method comprising: a) applying a die attach adhesive composition to a substrate,b) curing the die attach adhesive composition to form a die attach adhesive,c) plasma treating a surface of the die attach adhesive,d) plasma treating a surface of a semiconductor die,e) contacting the plasma treated surface of the semiconductor die with the plasma treated surface of the die attach adhesive,f) wire bonding the semiconductor die to the substrate,g) injection molding a silicone composition over the product of step f),optionally h) forming solder balls on a surface of the substrate opposite the die attach adhesive.

2. The method of claim 1, where the die attach adhesive comprises a silicone die attach adhesive.

3. (canceled)

4. The method of claim 1, where the silicone composition cures to form an over mold having a modulus of 25 to 1,000 megaPascals, and where the silicone composition has a viscosity of 80 to 3000 Poise and a curing profile such that the silicone composition cures in 30 to 120 seconds at a temperature of 80 to 240° C.

5. The method of claim 4, where step g) comprises: i) placing the product of step e) or the product of step f) in an open mold,ii) closing the mold to form a mold cavity,iii) heating the mold cavity,iv) injection molding a curable liquid into the mold cavity to overmold the semiconductor die on the substrate,v) opening the mold and removing the product of step iv), and optionally vi) post-curing the product of step v).

6. An electronic component comprising a substrate,a die attach adhesive on a surface of the substrate,a semiconductor die attached to the die attach adhesive,a wire bond connecting the semiconductor die to the substrate,an overmold over the semiconductor die, andoptionally solder balls on a surface of the substrate opposite the die attach adhesive;where the electronic component is prepared by the method of claim 1.

7. A method comprising: i) placing a semiconductor device in an open mold,ii) closing the mold to form a mold cavity,iii) heating the mold cavity,iv) injection molding a curable liquid comprising a silicone composition into the mold cavity to overmold the semiconductor device,v) opening the mold and removing the product of step iv), andoptionally vi) post-curing the product of step v).

8. The method of claim 7, where the semiconductor device comprises a substrate, a die attach adhesive, and an integrated circuit, wherein the integrated circuit is attached to a surface of the substrate through the die attach adhesive, and where the integrated circuit is wire bonded to the surface of the substrate.

9. The method of claim 7, where step ii) is carried out by applying a clamping force of 1 to 27 tons.

10. The method of claim 7, where the silicone composition forms an optically clear material upon cure.

11. The method of claim 7, where step iii) is performed at a temperature of 80 to 180° C.

12. The method of claim 7, wherein step iv) is carried out at an injection speed sufficient to provide a pressure of 0.6 to 2.0 MPa force in the mold cavity.

13. The method of claim 10, where the silicone composition has a viscosity of 80 to 3000 Poise.

14. The method of claim 10, where a cured product of the silicone composition has a modulus of 100 to 1,000 megaPascals.

15. A method comprising: a) applying a die attach adhesive composition to a substrate,b) attaching a semiconductor die to the die attach adhesive composition,c) curing the die attach adhesive composition to form a die attach adhesive, optionally d) wire bonding the semiconductor die to the substrate, ande) injection molding a curable liquid over the semiconductor device formed as the product of step c) or step d), wherein injection molding is carried out by a method comprising i) placing the semiconductor device in an open mold,ii) closing the mold to form a mold cavity,iii) heating the mold cavity,iv) injection molding a curable liquid into the mold cavity to overmold the semiconductor device,v) opening the mold and removing the product of step iv), andoptionally vi) post-curing the product of step v).

16. A method comprising: a) attaching a semiconductor die to a substrate to form a semiconductor device, andb) injection molding a curable liquid over the semiconductor device by a method comprising i) placing the semiconductor device in an open mold,ii) closing the mold to form a mold cavity,iii) heating the mold cavity,iv) injection molding a curable liquid comprising a silicone composition into the mold cavity to overmold the semiconductor device,v) opening the mold and removing the product of step iv), andoptionally vi) post-curing the product of step v).