JPH09232757A - Manufacture of multilayered circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the generation of warpage, to increase heat resistance and to enhance the reliable connection between circuits on insulating layers through non-through holes in a multilayered circuit board of a structure, wherein the connection between the circuits on the insulating layers is made through the non-through holes and a high-density wiring is provided. SOLUTION: In a method, wherein circuits are piled up on both surface or one surface of a core material printed-wiring board 1 via insulative layers 10 and 11 and the connection between36m or smaller.) is made to contain in the layers 10 and 11 to make a plating adhere uniformly to the wall surfaces of the holes 4 and 6. Moreover, the diameter of a glass fiber constituting the nonwoven glass faber is set in a diameter of 13μm or smaller to make glass, which is molten by the laser irradiation, hardly turn into recesses and projections on the wall surfaces of the holes at the time of the formation of the holes 4 and 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer circuit board in which circuits are stacked on both sides or one side of a core printed wiring board via insulating layers, and The present invention relates to a method for manufacturing a multilayer circuit board that enables high-density wiring by making connections through non-through holes.

[0002]

2. Description of the Related Art In recent years, demands for miniaturization and multi-functionality of electronic devices have been remarkably increasing, and wiring densities of printed wiring boards incorporated and used in electronic devices have been increasing. In order to increase the wiring density, the printed wiring board is a multi-layer circuit board in which circuits are also arranged in the inner layers via insulating layers, and the number of layers has been increased and the circuit line width has been reduced. Therefore, the number of through holes (holes penetrating the multilayer circuit board) for electrically connecting circuits between insulating layers is also increasing.
If the number of the through holes increases, the area available for arranging the circuits decreases, so that high density wiring cannot be performed.

Therefore, there has been proposed a multilayer circuit board in which circuits between insulating layers are connected by non-through holes to enhance the degree of freedom in circuit design. As shown in FIG. 2, a circuit 3 is provided on a core printed wiring board 1 via an insulating resin layer 2 (made of resin only), and a non-through hole 4 is formed in the insulating resin layer 2.
The circuit 3 and the inner layer circuit (the circuit of the core material printed wiring board 1 in FIG. 2) are connected through the non-through holes 4. When the number of layers of the circuit is further increased, the stacking of the insulating resin layer 2 and the circuit 3 and the connection of the circuit between the insulating layers in the non-through holes 4 are repeated. If necessary, the through hole 5 is provided at the end. The insulating resin layer 2 may be made of only a resin, or may be made of an organic fiber nonwoven fabric impregnated with a thermosetting resin. In addition, the circuit 3 is formed by etching a copper foil integrated with the insulating resin layer 2, or by forming electroless plating or printing a conductive paint on the insulating resin layer 2. However, if a layer made of only a thermosetting resin is used for the insulating resin layers that are sequentially stacked above and below the printed wiring board that serves as the core material, it is difficult to mix the inorganic filler, and the coefficient of thermal expansion in the thickness direction increases. Also, the adhesive strength between the circuit and the insulating resin layer is not so great. The insulating resin layer on the surface easily absorbs moisture, and there is a risk that the insulating resin layer will peel off due to the heat in the reflow oven during component mounting.If the insulating resin layer is composed of an organic fiber nonwoven fabric impregnated with a thermosetting resin, However, the heat in the reflow furnace may melt or soften the organic fiber nonwoven fabric, so that the thermosetting resin and the organic fiber nonwoven fabric may be separated at the interface. When such peeling occurs, moisture absorption causes a significant decrease in insulation resistance. Furthermore, since the multilayer circuit board is formed by stacking an insulating resin layer having low mechanical strength on a core material printed wiring board, the mechanical strength is low and warpage occurs in the reflow furnace. In particular, the tendency becomes remarkable as the thickness of the core printed wiring board becomes thin.

[0004]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to suppress warpage in a multilayer circuit board which enables high density wiring by connecting circuits between insulating layers with non-through holes. , To improve heat resistance. Further, it is to improve the connection reliability of the circuit between the insulating layers, particularly the connection reliability in the non-through holes.

[0005]

In order to solve the above-mentioned problems, a method for manufacturing a multilayer circuit board according to the present invention comprises forming one or more circuits on both sides or one side of a core printed wiring board with an insulating layer interposed therebetween. In the method having the step of connecting the circuits through the insulating layer with the non-through holes, the insulating layer for connecting at least the circuits among the insulating layers with the non-through holes,
It is composed of thermosetting resin impregnated glass nonwoven fabric. In the multilayer circuit board manufactured as described above, the resin content in the insulating layer made of the thermosetting resin-impregnated glass nonwoven fabric is 50 to 97% by weight.
It is. The structure in which the glass non-woven fabric is arranged in the insulating layer increases the mechanical strength of the multilayer circuit board and suppresses warpage. Also, the heat resistance is improved. Furthermore, since the coefficient of thermal expansion in the thickness direction of the insulating layer is small, the connection reliability between the circuits in the non-through holes can be improved. An insulating layer made of thermosetting resin impregnated glass non-woven fabric should be used for all the insulating layers that are stacked on the core printed wiring board, but at least insulation between circuits through the insulating layer should be performed with non-through holes. The layer may be an insulating layer made of a thermosetting resin-impregnated glass nonwoven fabric.

The non-through hole is formed through the following steps (a) and (b). (A) A step of forming one or more circuits on both sides or one side of a core printed wiring board via a thermosetting resin-impregnated glass nonwoven fabric layer. (B) A step of performing non-through hole drilling on the insulating layer made of a thermosetting resin-impregnated glass nonwoven fabric by laser irradiation. Although light energy such as photolithography cannot be used for drilling holes in the insulating layer, non-through holes of φ0.1 mm can be easily formed by using high-energy light such as laser light. In particular, since glass fibers are dispersed in the glass non-woven fabric, there are few irregularities on the hole wall surface formed by laser irradiation.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the manufacturing method according to the present invention, the core printed wiring board is, for example, a wiring board having a circuit formed on one side or both sides or a multilayer circuit board having a circuit in an inner layer. These may be any of a rigid printed wiring board, a flexible printed wiring board and a metal core printed wiring board. Rigid printed wiring boards are made of glass woven fabric, glass non-woven fabric, etc. as a base material, and are impregnated with thermosetting resin or heat resistant thermoplastic resin. It is a wiring board. The flexible printed wiring board is a flexible printed wiring board using a film such as polyester or polyimide as an insulating substrate. The metal core printed wiring board is copper,
This is a printed wiring board which is used as an insulating substrate by coating a thermosetting resin on a metal plate such as aluminum or iron. A circuit forming method for these core material printed wiring boards is not particularly limited, such as a subtractive method and an additive method which are usually used. Thermosetting resins include polyimide, phenol resin, cyanate resin, cyanate ester resin, epoxy resin,
Unsaturated polyester can be used without particular limitation.

Circuits are sequentially stacked on the core printed wiring board as described above through an insulating layer made of a thermosetting resin-impregnated glass nonwoven fabric. By adding an inorganic filler to the insulating layer, the sled is formed. The effect of suppressing is further increased. The type of the inorganic filler is generally used such as aluminum hydroxide, clay, silica, talc and is not particularly limited. The glass composition of the glass nonwoven fabric is
The composition is E glass, D glass, Q glass, S glass, or the like, and is not particularly limited. Further, a glass non-woven fabric formed by making glass chops into which glass fibers having different glass compositions are mixed may be adopted. The circuit on the insulating layer made of thermosetting resin impregnated glass non-woven fabric should be formed by etching the metal foil integrated with this insulating layer, printing conductive paint on the specified circuit pattern, or by electroless plating. You can The metal foil is a copper foil, an aluminum foil, a nickel foil, or the like, and the kind and thickness of the metal foil are not particularly limited as long as they have good conductivity. If necessary, a metal foil with an adhesive can be used. In this case, as the adhesive, a general-purpose adhesive for metal foil such as phenol resin, epoxy resin, butyral resin, polyester, polyurethane, or a mixture thereof can be used.

In order to connect a circuit on an insulating layer made of a thermosetting resin-impregnated glass non-woven fabric and a circuit on an inner layer of the insulating layer, a non-through hole is opened in the insulating layer by laser irradiation.
Copper plating is applied to the hole wall. When the average particle diameter of the inorganic filler contained in the insulating layer is set to 20 μm or less, the plating can be applied uniformly not only to the wall of the non-through hole but also to the wall surface of the through hole formed in the last step. Therefore, the connection reliability in the non-through hole and the through hole is improved. In addition, the diameter of the glass fiber forming the glass nonwoven fabric is 13 μm.
In the following case, the glass melted by the laser irradiation during the formation of the non-through holes is unlikely to become uneven on the wall surface of the hole, which is advantageous in uniformly depositing the copper plating on the wall surface of the hole.

The resin of each insulating layer of the multilayer circuit board (including the insulating layer of the core printed wiring board) contains a halogen-containing organic compound, a flame-retardant aid such as antimony oxide, and other organic substances in order to impart flame resistance. Fillers, colorants and the like may be added.

[0011]

【Example】

Example 1 (Production of core printed wiring board) Epoxy resin (“Ep-1001” manufactured by Yuka Shell, epoxy equivalent: 480) 10
0 parts by weight, dicyandiamide 3 parts by weight, 2-
0.2 parts by weight of ethyl 4-methylimidazole was mixed to prepare a varnish (A). 200 μm thick glass woven cloth (“7628” manufactured by Asahi Schwebel, glass fiber diameter 9 μm
The m) was impregnated with the varnish (A) and dried to prepare a prepreg (A) having a resin content of 42% by weight. Prepreg (A)
Copper foil (thickness 18 μm) is placed on the top and bottom of the four sheets and heat-pressed for 60 minutes at a temperature of 170 ° C. and a pressure of 40 kgf / cm ² to form a copper-clad laminate with a thickness of 0.4 mm. (A)
I got A predetermined circuit is formed on the copper-clad laminate (A) by etching, and the surface of the circuit is blackened in order to improve the adhesiveness in a later step to obtain a core printed wiring board 1 (Fig. 1 ( a)).

(Multilayering process 1) The thickness of the varnish (A) is set to 35
0 μm glass non-woven fabric (“EPM44
45 ", glass fiber diameter 10 μm) and dried to prepare a prepreg (B) having a resin amount of 78% by weight. The prepreg (B) is superposed on the upper and lower surfaces of the core printed wiring board 1 one by one, and copper foil (thickness 18 μm) is placed on the upper and lower surfaces thereof,
A copper-clad laminate (B) was obtained by heat-press molding for 60 minutes at a temperature of 170 ° C. and a pressure of 40 kgf / cm ² (FIG. 1).
(B)). Copper in a portion of the copper-clad laminate (B) where a non-through hole is formed is removed by etching, and a non-through hole is opened in the portion by laser irradiation to expose the circuit of the core printed wiring board 1. Then, the same circuit, the hole wall and the copper foil on the surface were plated with copper. The copper foil on the plated surface was etched to form a predetermined circuit, and the circuit surface was subjected to blackening treatment in order to improve the adhesiveness in a later step. This is a configuration in which the circuits 3 are provided on both surfaces of the core printed wiring board 1 with the insulating layer 10 made of an epoxy resin-impregnated glass nonwoven fabric interposed therebetween.
The circuit 3 and the circuit of the core printed wiring board 1 are appropriately connected to each other through non-through holes 4 in the insulating layer 10 (holes formed only in the insulating layer 10 made of epoxy resin-impregnated glass nonwoven fabric) (FIG. 1 (c)). )).

(Multilayering step 2) A prepreg (B) and a copper foil (thickness 1) are formed on the upper and lower surfaces of the printed wiring board which has undergone the multilayering step 1.
8 μm) in this order and heat-pressed in the same manner as above to obtain a copper-clad laminate (C) (FIG. 1 (d)). The copper of the copper-clad laminate (C) where the non-through holes are to be formed is removed by etching, and the non-through holes 6 are opened in that portion by laser irradiation.
The inner layer circuit was exposed. Moreover, the through hole 5 was opened by the NC drill machine. Then, the exposed inner layer circuit, the non-through holes 6 and the hole walls of the through holes 5 and the copper foil on the surface were plated with copper. The copper foil on the plated surface was etched to form a predetermined circuit 7. The circuit 7 on the surface and the circuit in one of the inner layers are connected to each other through a non-penetrating hole 6 (a hole formed only in the insulating layer 11 made of the epoxy resin-impregnated glass nonwoven fabric) of the insulating layer 11 made of the epoxy resin-impregnated glass nonwoven fabric. ing. Further, the circuits of the respective layers are appropriately connected by the through holes 5 (FIG. 1 (e)).

In this embodiment, the multi-layering process is carried out only twice, but when the number of layers in the circuit is increased, the same multi-layering process is further repeated.

Example 2 The varnish (A) used in Example 1 had an average particle size of 18 μm.
A mixture of 40 parts by weight of talc of m was used. A multilayer printed wiring board was manufactured in the same manner as in Example 1 except for the above.

Example 3 The varnish (A) used in Example 1 had an average particle size of 8 μm.
Was further mixed with 40 parts by weight of talc.
A multilayer printed wiring board was manufactured in the same manner as in Example 1 except for the above.

Example 4 The varnish (A) used in Example 1 had an average particle size of 20 μm.
A mixture of 40 parts by weight of talc of m was used. A multilayer printed wiring board was manufactured in the same manner as in Example 1 except for the above.

Example 5 The varnish (A) used in Example 1 has an average particle size of 22 μm.
A mixture of 40 parts by weight of talc of m was used. A multilayer printed wiring board was manufactured in the same manner as in Example 1 except for the above.

Example 6 A glass nonwoven fabric having a glass fiber diameter of 7 μm was used as the glass nonwoven fabric. Otherwise, Example 1
A multilayer printed wiring board was manufactured in the same manner as in.

Example 7 A glass nonwoven fabric having a glass fiber diameter of 13 μm was used as the glass nonwoven fabric. A multilayer printed wiring board was manufactured in the same manner as in Example 1 except for the above.

Example 8 A glass nonwoven fabric having a glass fiber diameter of 15 μm was used as the glass nonwoven fabric. A multilayer printed wiring board was manufactured in the same manner as in Example 1 except for the above.

Conventional Example 1 The varnish (A) used in Example 1 was applied to the roughened surface of a copper foil and dried to prepare a copper foil with an insulating resin layer (A) having a thickness of 50 μm. The insulating resin layer surface of the copper foil with an insulating resin layer (A) is overlaid on the upper and lower surfaces of the core printed wiring board used in Example 1, and heated and pressed for 60 minutes under the conditions of a temperature of 170 ° C. and a pressure of 40 kgf / cm ^2. It shape | molded and the copper clad laminated board (D) was obtained. The copper of the copper-clad laminate (D) where the non-through holes are to be formed is removed by etching, and the non-through holes are made in that portion by laser irradiation.
The core printed circuit board circuit is exposed. Then, the same circuit, the hole wall and the copper foil on the surface were plated with copper. The copper foil on the plated surface was etched to form a predetermined circuit, and the circuit surface was subjected to blackening treatment in order to improve the adhesiveness in a later step. Furthermore, the insulating resin layer surface of the copper foil (A) with an insulating resin layer is laid on the upper and lower surfaces of the printed wiring board that has undergone the above steps, and the temperature is 170 ° C. and the pressure is 40 kgf / cm ^2.
It was heated and pressed for 0 minutes to obtain a copper-clad laminate (E). Copper was removed by etching from the portion of the copper-clad laminate (E) where a non-through hole was to be formed, and a non-through hole was opened in that portion by laser irradiation to expose the inner layer circuit. In addition, through holes were opened with an NC drill machine. Then, copper was plated on the hole walls of the non-through holes and the through holes and the copper foil on the surface. The copper foil on the plated surface was etched to form a predetermined circuit.

Conventional Example 2 The varnish (A) used in Example 1 was impregnated into an aramid fiber nonwoven fabric having a thickness of 150 μm and dried to prepare a prepreg (C) having a resin amount of 85% by weight. A prepreg (C) and a roughened surface of a copper foil were overlaid on the upper and lower surfaces of the core printed wiring board used in Example 1, and the temperature was 170 ° C. and the pressure was 40 kgf / cm ^2.
Copper-clad laminate (F) by heat and pressure molding for 60 minutes under the conditions
I got Copper in a portion of the copper-clad laminate (F) where a non-through hole is to be formed is removed by etching, and a non-through hole is opened in the portion by laser irradiation to expose the circuit of the core printed wiring board. Then, the same circuit, the hole wall and the copper foil on the surface were plated with copper. The copper foil on the plated surface was etched to form a predetermined circuit, and the circuit surface was subjected to blackening treatment in order to improve the adhesiveness in a later step. Furthermore, the prepreg (C) and the roughened surface of the copper foil are overlaid on the upper and lower surfaces of the printed wiring board that has undergone the above steps, and the temperature is 170 ° C. and the pressure is 40 kg.
A copper-clad laminate (G) was obtained by heat-press molding for 60 minutes under the condition of f / cm ² . Copper was removed by etching from a portion of the copper-clad laminate (G) where a non-through hole was to be formed, and a non-through hole was opened in that portion by laser irradiation to expose the inner layer circuit. In addition, through holes were opened with an NC drill machine. Then, copper was plated on the hole walls of the non-through holes and the through holes and the copper foil on the surface. The copper foil on the plated surface was etched to form a predetermined circuit.

Conventional Example 3 A glass woven cloth having a thickness of 100 μm was impregnated with the varnish (A) used in Example 1 and dried to prepare a prepreg (D) having a resin amount of 42% by weight. The prepreg (D) and the roughened surface of the copper foil are overlaid on the upper and lower surfaces of the core printed wiring board used in Example 1 and heat-pressed for 60 minutes under the conditions of a temperature of 170 ° C. and a pressure of 40 kgf / cm ^2. To obtain a copper-clad laminate (H).
Copper in a portion of the copper-clad laminate (H) where a non-through hole is to be formed is removed by etching, and a non-through hole is opened in the portion by laser irradiation to expose the circuit of the core printed wiring board. Then, the same circuit, the hole wall and the copper foil on the surface were plated with copper.
The copper foil on the plated surface was etched to form a predetermined circuit, and the circuit surface was subjected to blackening treatment in order to improve the adhesiveness in a later step. Further, a prepreg (D) and a roughened surface of a copper foil are superposed on the upper and lower surfaces of the printed wiring board that has undergone the above steps, and heated and pressed for 60 minutes under the conditions of a temperature of 170 ° C. and a pressure of 40 kgf / cm ^2. A copper-clad laminate (I) was obtained. Copper in a portion of the copper-clad laminate (I) where a non-through hole was formed was removed by etching, and a non-through hole was opened in the portion by laser irradiation to expose an inner layer circuit. Further, through holes were opened by an NC drill machine, and copper was plated on the hole walls of the through holes and the copper foil on the surface. The copper foil on the plated surface was etched to form a predetermined circuit.

Table 1 shows the evaluation results of the multilayer printed wiring boards of the above examples and conventional examples. The evaluation method is as follows. Deflection: After passing a test piece with a length of 300 mm and a width of 10 mm through a reflow device (maximum temperature of 250 ° C), measure the maximum value of the lifted amount at the four corners of the test piece in a flat place. Heat resistance: length 300 mm After passing a test piece with a width of 10 mm through a reflow device (maximum temperature 250 ° C.), the presence or absence of peeling of the surface layer of the test piece is observed. ○: No peeling ×: With peeling Connection reliability: The circuit pattern of the cross section is shown in FIG. Prepare a multi-layer circuit board for evaluation as shown in Fig.
A cycle until the conduction resistance increases by 10% from the initial value by repeating the 10 second cooling / heating cycle (non-through hole diameter: 0.2
mm, through hole diameter: 0.4 mm)

[0026]

[Table 1]

[0027]

As is apparent from Table 1, in the multilayer board manufactured by the method according to the present invention, in the structure in which the circuit connection between the insulating layers is performed by the non-through hole, the connection reliability of the circuit between the warp and the insulating layer is improved. Also, the heat resistance can be made excellent. If the insulating resin layer contains an inorganic filler, the warp can be further reduced (Examples 2, 3, 4, 5), and if the average particle diameter of the inorganic filler is 20 μm or less, through holes and The circuit connection reliability between the insulating layers connected by the non-through holes can be further improved (Examples 2, 3 and 4). Further, when making a non-through hole by laser irradiation, if the glass fiber diameter of the glass woven fabric of the surface insulating layer is 10 μm or less, the circuit connection reliability between the insulating layers connected by the non-through hole can be further enhanced. (Examples 1 and 6).

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of an example according to the present invention.

FIG. 2 is a cross-sectional view of a conventional multilayer printed wiring board.

FIG. 3 is an explanatory diagram of a cross-sectional circuit pattern of a multilayer printed wiring board for evaluating connection reliability of a circuit between insulating layers.

[Explanation of symbols]

 1: Core printed wiring board 2: Insulating resin layer 3: Circuit 4: Non-through hole 5: Through hole 6: Non-through hole 7: Circuit 10, 11: Insulating layer

Claims (5)

[Claims] 1. A multilayer circuit board having a step of forming one or more circuits on both sides or one side of a core printed wiring board via an insulating layer and connecting circuits via the insulating layer with non-through holes. In the manufacturing method, a method for manufacturing a multilayer circuit board, characterized in that at least an insulating layer of the insulating layers for connecting circuits with a non-through hole is made of a thermosetting resin-impregnated glass nonwoven fabric. 2. The method for producing a multilayer circuit board according to claim 1, wherein the insulating layer made of a thermosetting resin-impregnated glass nonwoven fabric contains an inorganic filler. 3. The method for producing a multilayer circuit board according to claim 2, wherein the average particle diameter of the inorganic filler is 20 μm or less. 4. A method for manufacturing a multilayer circuit board, which comprises the following steps (a) and (b). (A) A step of forming one or more circuits on both sides or one side of a core printed wiring board via a thermosetting resin-impregnated glass nonwoven fabric layer. (B) A step of performing non-penetrating drilling on the surface insulating layer made of a thermosetting resin-impregnated glass nonwoven fabric by laser irradiation. 5. The method for producing a multilayer circuit board according to claim 4, wherein the glass fiber constituting the glass nonwoven fabric has a diameter of 13 μm or less.