Prepreg and process for manufacturing same

• US 20020168504A1
• Filed: 10/29/2001
• Published: 11/14/2002
• Est. Priority Date: 03/13/2001
• Status: Active Grant

• Current Assignee: Sumitomo Bakelite Company Limited
• Original Assignee: Sumitomo Bakelite Company Limited
• Inventors: Yamaji, Takashi, Komatsu, Mamoru
• Granted Patent: US 6,569,513 B2
• Time in Patent Office: Days
• US Class Current: 428/209
• CPC Class Codes: B29B 15/122 with a matrix in liquid form, e.g. as melt, solution or latex
• CPC Class Codes: B29B 15/125 by dipping
• CPC Class Codes: B29K 2063/00 Use of EP, i.e. epoxy resins or derivatives thereof, as moulding material
• CPC Class Codes: C08J 2363/00 Characterised by the use of epoxy resins; Derivatives of epoxy resins
• CPC Class Codes: C08J 3/245 Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
• CPC Class Codes: C08J 5/244 using glass fibres
• CPC Class Codes: H05K 1/0366 reinforced, e.g. by fibres, fabrics H05K1/036 takes precedence
• CPC Class Codes: H05K 2203/0783 Using solvent, e.g. for cleaning; Regulating solvent content of pastes or coatings for adjusting the viscosity
• CPC Class Codes: H05K 2203/1476 Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning
• CPC Class Codes: Y10S 428/901 Printed circuit
• CPC Class Codes: Y10T 428/24917 including metal layer
• CPC Class Codes: Y10T 428/31529 Next to metal
• CPC Class Codes: Y10T 428/31623 Next to polyamide or polyimide

Abstract

A prepreg exhibiting excellent formability and producing laminated boards and multiple layer circuit boards exhibiting high thickness precision is disclosed. The prepreg comprises an inner layer made from a glass fiber substrate, having a weight of 40 g or more and less than 115 g per square meter and an air permeability or 20 cm³/cm²/sec or less, impregnated with an epoxy resin, and an outer layer of an epoxy resin coating provided on at least one side of the inner layer, wherein the epoxy resin reaction rate in the inner layer is 85% or more and the epoxy resin reaction rate in the outer layer is 60% or less.

Claims

1. A prepreg comprising an inner layer made from a glass fiber substrate, having a weight of 40 g or more and less than 115 g per square meter and an air permeability of 20 cm³/cm²/sec or less, impregnated with an epoxy resin, and an outer layer of an epoxy resin coating provided on at least one side of the inner layer, wherein the epoxy resin reaction rate in the inner layer is 85% or more and the epoxy resin reaction rate in the outer layer is 60% or less.

2. The prepreg according to claim 1, wherein the reaction rate of the epoxy resin in the inner layer is 90 to 95% and that of the outer layer is 20% or less.

3. The prepreg according to claim 1, wherein the weight ratio (R)/(G) of the epoxy resin (R) and the glass fiber substrate (G) in the inner layer is 0.43 or more.

4. The prepreg according to claim 1, wherein the weight ratio (R)/(G) of the epoxy resin (R) and the glass fiber substrate (G) in the inner layer is 0.53 to 2.40.

5. The prepreg according to claim 1, wherein the glass fiber substrate has a weight of 47 to 105 g per square meter and an air permeability of 5 to 10 cm³/cm²/sec.

6. The prepreg according to claim 1, wherein the prepreg, when used for insulating the circuit layers in multiple-layer print circuit boards, has a weight of the epoxy resin per unit area in each outer layer greater than the value A determined by the following formula and less than 1.5A.

A=(1−

b/10²)×

c/10⁴×

d 

 

(1)

wherein A is the weight of the resin per unit area of the outer layer (g/cm²), b is the amount of residual copper (%) in a circuit layer facing the outer layer of the prepreg, c indicates the thickness (μ

m) of the circuit copper foil, and d is the specific gravity (g/cm³) of the outer layer resin.

7. The prepreg according to claim 1, wherein the outer layer is provided on both sides of the inner layer and the thickness of the outer layer epoxy resin on the different side of the inner layer is not identical.

8. A laminated board prepared by forming one prepreg or two or more layered prepregs according to any one of claims 1 to 7.

9. The laminated board according to claim 8, which is a multiple-layer board of copper-clad laminate or multiple-layer printed circuit board.

10. A process for manufacturing a prepreg comprising (a) a step of impregnating a glass fiber substrate, having a weight of 40 g or more and less than 115 g per square meter and an air permeability of 20 cm³/cm²/sec or less, with a solvent, (b) a step of impregnating the solvent-impregnated glass fiber substrate with epoxy resin, (c) a step of heating the epoxy resin-impregnated glass fiber substrate, (d) a step of further impregnating the epoxy resin-impregnated glass fiber substrate, in which the epoxy resin has been cured, with the epoxy resin, and (e) a step of heating the last-obtained epoxy resin-impregnated glass fiber substrate, wherein the epoxy resin reaction rate in the inner layer is 85% or more and the epoxy resin reaction rate in the outer layer is 60% or less.

11. The process for manufacturing a prepreg according to claim 10, wherein the reaction rate of the epoxy resin in the inner layer is 90 to 95% and that of the outer layer is 0 to 20%.

12. The process for manufacturing a prepreg according to claim 10, wherein the solvent impregnated in the glass fiber substrate in the step (a) is dimethyl formamide, methyl cellosolve, or methyl ethyl ketone.

13. The process for manufacturing a prepreg according to claim 10, wherein the time for which the solvent is impregnated in the glass fiber substrate in the step (a) is 0.1 to 1 minute at room temperature.

14. The process for manufacturing a prepreg according to claim 10, wherein, after the step (a) and before the step (b), the solvent-impregnated glass fiber substrate obtained in the step (a) is passed through an air stream for 1 to 5 minutes at a temperature lower than the boiling point of the solvent used in the step (a).

15. The process for manufacturing a prepreg according to claim 14, wherein the amount of solvent in the solvent-impregnated glass fiber substrate after passing the substrate through an air stream and before the step (b) is 16 to 25 parts by weight per 100 parts by weight of the glass fiber substrate.

16. The process for manufacturing a prepreg according to claim 10, wherein the time for which the epoxy resin is impregnated in the glass fiber substrate in the step (b) is 0.1 to 1 minute at room temperature.

17. The process for manufacturing a prepreg according to claim 10, wherein the heating conditions in the step (c) are 140 to 200°

C. for 1 to 5 minutes.

18. The process for manufacturing a prepreg according to claim 10, wherein the time for which the epoxy resin is impregnated in the glass fiber substrate in the step (d) is 0.1 to 1 minute at room temperature.

19. The process for manufacturing a prepreg according to claim 10, wherein the heating conditions under which the epoxy resin impregnated glass fiber substrate in the step (e) are 140 to 200°

C. for 1 to 5 minutes.