JPH06260767A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a multilayer printed wiring board at a low cost even if an outermost conductor circuit is formed through an additive method. CONSTITUTION:A prepreg 2 is arranged on the outside of an inner board 1, and a filmy additive adhesive agent 3 is provided to the outside of the prepreg 2 to serve as an adhesive layer 13. The prepreg 2 and the inner board 1 are thermocompressed together with an autoclave 8 for the formation of a laminate 5 provided with the adhesive layer 13 as an outermost layer. Then, the adhesive layer 13 is roughened, and then a conductor circuit is formed on the outermost layer of the laminate 5 through an additive method.

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 printed wiring board, and more particularly to a method for manufacturing a multilayer printed wiring board in which an outermost conductor circuit is formed by an additive method.

[0002]

2. Description of the Related Art In recent years, miniaturization, high performance and multi-functionalization of electronic devices have been advanced, and multilayer printed wiring boards used therein are required to have high density and high reliability by fine patterns. ing.

Conventionally, as a method of forming a conductor circuit on a multilayer printed wiring board, a so-called prepreg and a copper foil are heated and pressed on the outer side of an inner layer substrate to form a laminated body, and the subtracted body is etched. The law is widely practiced. It is known that this method can form a conductor circuit having excellent adhesion with the prepreg on the outermost layer of the laminate. On the other hand, according to this method, the etching depth when forming a pattern by etching is large, and the undercut is likely to be large. Therefore, it has been pointed out in recent years that it is difficult to obtain a highly accurate fine pattern and it is difficult to cope with high density.

As an alternative method, an additive method is known in which a conductor circuit is formed on the outermost layer of the laminated body only by electroless plating without using a copper foil when the laminated body is formed by heating and pressing. . According to this method, there is an advantage that a high-precision fine pattern can be obtained,
Additive law has been receiving a lot of attention in recent years.

An example of a method of forming the outermost conductor circuit by the additive process will be described with reference to FIGS. First, an inner layer substrate 21 having an inner layer conductor circuit 20 formed at a predetermined position and a pair of prepregs 22 are laminated,
Further, a pair of mirror surface plates 24 are arranged on both the front and back sides of the sheet with a release sheet 23 therebetween (see FIG. 5). By heating under pressure in this state, the B-stage thermosetting resin impregnated in the glass cloth of the prepreg 22 is cured, and the inner layer substrate 21 and the prepreg 22 are integrated (see FIG. 6). An adhesive layer is provided on the surface of the obtained laminated body 25 using the adhesive 26 for additive (see FIG. 7), and then an anchor is formed by roughening the adhesive layer. In this case, as the adhesive, an adhesive containing a filler such as butadiene rubber in a matrix of a thermosetting resin such as an epoxy resin is generally used.

Further, after the catalyst nuclei necessary for the first metal deposition in electroless plating are applied to the roughened adhesive layer, a plating resist layer is formed at a desired position. Here, after the activation treatment of the catalyst nuclei, electroless copper plating or the like is applied to the portions other than the plating resist layer. As a result, a desired conductor circuit is formed on the outermost layer of the laminate.

[0007]

By the way, in the conventional additive process, the adhesive layer is generally formed using either a liquid adhesive or a semi-cured film adhesive. When the former is selected, the liquid adhesive is applied to the surface of the laminate by a roll coater method, a dipping dip method, a spray method or the like. On the other hand, when the latter is selected, the film adhesive is adhered to the surface of the laminate by a heating / pressing method or a laminating method using a heat roller.

However, no matter which adhesive is selected, separate steps such as a coating step and a heating and pressing step are required, so that the manufacturing cost is higher than that of the subtractive method. Further, in the heating and pressing method, it is necessary to further dispose the film adhesive 26, the release sheet 23 and the mirror surface plate 24 on the laminated body 25 as shown in FIGS. As a result, the process becomes complicated.

As described above, the advantage that a fine pattern with high precision can be obtained, but also the drawbacks such as high cost, makes the use range of the multilayer printed wiring board by the additive method narrow in high-class computers and the like. It was limited to the field.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to manufacture a multilayer printed wiring board at a low cost despite forming an outermost conductor circuit by an additive method. It is to provide a method for manufacturing a multilayer printed wiring board.

[0011]

In order to solve the above problems, in the invention described in claim 1, a prepreg is arranged outside the inner layer substrate, and a film-like additive serving as an adhesive layer is further formed outside the prepreg. A laminate having an adhesive layer as the outermost layer is formed by arranging an adhesive for heating and performing heat and pressure, and then the laminate is subjected to a roughening treatment, and then the laminate is obtained by an additive method. The gist of the invention is to form a conductor circuit on the outermost layer.

In the invention according to claim 2, an adhesive layer is previously formed on one surface of the prepreg by using a liquid additive adhesive, and the adhesive layer non-forming surface side of the prepreg and the inner layer substrate side. By laminating them so that they face each other and performing heating and pressing, a laminated body having an adhesive layer as the outermost layer is formed, and then the adhesive layer is subjected to a roughening treatment, followed by the additive method. The main point is to form a conductor circuit on the outermost layer of the laminate.

[0013]

According to the method of the present invention, the laminate having the adhesive layer as the outermost layer is formed by one heating and pressing step, so that the coating which has been conventionally performed as a separate step for forming the adhesive layer. It eliminates the need for processes and heating / pressing processes. Therefore, the number of steps for manufacturing the multilayer printed wiring board is reduced, and the manufacturing cost can be reduced.

[0014]

EXAMPLE 1 Example 1 embodying the present invention will be described in detail below with reference to FIGS.

Step (1): First, in this embodiment, an inner layer substrate 1, a prepreg 2 and a film-shaped adhesive agent 3 for additive were prepared (see FIG. 1). The inner layer substrate 1 includes an insulating base material 1a such as a prepreg and a copper foil 1b.
It is produced by using a copper-clad laminate having the above attached as a starting material. In this embodiment, a copper clad laminate having a thickness of 1.6 mm was used to etch the copper foils 1b on both sides of the laminate according to the subtractive method to form the conductor circuit 4 of the inner layer at a predetermined portion.

Further, in this embodiment, as the additive adhesive 3, a varnish in which a filler made of epoxy resin fine powder is dispersed in a matrix made of epoxy resin has a thickness of 50 μm.
m in the form of a film (hereinafter referred to as "adhesive film 3")
Called). The adhesive film 3 is in an incompletely cured state (B stage) at this point.

Further, in this embodiment, a 100 μm thick prepreg 2 in which glass cloth is impregnated with a thermosetting epoxy resin was selected. Then, two prepregs 2 were arranged on the outer side of the inner layer substrate 1, and two adhesive film 3 were further arranged on the outer side thereof (see FIG. 1). In addition, these 1,
The layers 2 and 3 are to be integrated into one another in the subsequent heating and pressing process to form the laminated body 5.

Step (2): Further, a laminate of the inner layer substrate 1, the prepreg 2 and the adhesive film 3 is sandwiched between a pair of mirror surface plates 6, and a space made of Teflon (trademark) or the like is provided between them. The mold sheet 7 was interposed (see FIG. 2).

Step (3): Next, the laminate is transferred to the autoclave 8, and the laminate is covered with the rubber sheet 9 and the rubber sheet 9 and the inner bottom surface 8 of the autoclave 8.
The sealing material 10 was interposed between the a and a (see FIG. 3). Further, a hose 12 is arranged as a means for bleeding air from the space 11 formed by the rubber sheet 9 and the inner bottom surface 8a.

In this state, under predetermined conditions (under N ₂ atmosphere, 1
The heating and pressing (so-called isotropic pressing) was performed at 70 ° C. for 2 hours. In this Example 1, the press pressure was set to about 9 kg / cm ² in order to prevent the filler from being crushed and deformed due to the high press pressure.

As a result of the heating and pressing, the outermost layer of the laminate 5 has a thickness of 50 μm and a surface roughness of 2 μm to 8 μm.
The adhesive layer 13 having a certain degree was formed. Step (4): Next, after removing the mirror surface plate 6 and the release sheet 7 from the laminated body 5, a through hole serving as a through hole is formed in the laminated body 5. Then, the laminate 5 was immersed in an aqueous solution of chromic acid (Cr ₂ O ₃ ) 700 g / l at 70 ° C. for 15 minutes to roughen the surface of the adhesive layer 13.

The matrix forming the adhesive layer 13 is hardly soluble in the solution, and the filler dispersed therein is soluble in the solution. Therefore, this process
A roughened adhesive layer having a large number of anchor recesses having a diameter of about several μm is formed on the surface. Then, the laminate 5 was immersed in a neutralizing solution (made by Shipley) and washed with water.

Step (5): Pd catalyst nucleus application, resist formation, catalyst nucleus activation, electroless copper plating, etc. are carried out in accordance with the ordinary additive method, and a conductor circuit is formed on the outermost layer of the laminate 5. A multilayer printed wiring board having the above was obtained.

When the pattern adhesion strength (peel strength) of the conductor circuit formed in the outermost layer was investigated, the measured value was obtained by a conventional method such as a roll coater method or a dry film laminating method. It was almost the same as the measured value.

Further, according to the method of this embodiment, since the laminate 5 having the adhesive layer 13 as the outermost layer is formed by one heating and pressing step, the number of manufacturing steps is reduced and the manufacturing cost is reduced. It became a result. [Embodiment 2] Next, Embodiment 2 embodying the present invention will be described with reference to FIG.
It will be described in detail based on.

Step (1): In this embodiment, first, the same inner layer substrate 1 and prepreg 2 as in Embodiment 1 are prepared, and a liquid additive adhesive for preliminarily forming an adhesive layer on the prepreg 2. Prepared.

The liquid additive adhesive used in this example is a matrix of thermosetting epoxy resin powder in which a filler of epoxy resin fine powder is dispersed (hereinafter referred to as "adhesive varnish"). Is.

Then, a B-stage adhesive varnish is applied to one surface of the prepreg 2 by using a roll coater to obtain a thickness of 7
An adhesive layer 14 of 0 μm was formed (see FIG. 4). After this,
The prepreg 2 and the inner layer substrate 1 were laminated so that the adhesive layer 14 was on the outer layer side.

Step (2): Next, the prepreg 2 having the adhesive layer 13 formed thereon and the inner layer substrate 1 are superposed on each other.
As in Example 1, the sheet was sandwiched between the release sheet 7 and the mirror plate 6. Then, after transferring the laminate to the autoclave 8, the same heating and pressing as in Example 1 was performed to integrate the prepreg 2 having the adhesive layer 13 and the inner layer substrate 1.

Step (3): Step (4) of Example 1 below
And according to (5), drilling, roughening, Pd catalyst nucleation,
Resist formation, activation of catalyst nuclei, electroless copper plating, etc. were carried out to obtain a multilayer printed wiring board having a conductor circuit in the outermost layer of the laminate 5.

When the pattern adhesion strength (peel strength) of the conductor circuit formed in the outermost layer was investigated, the measured value was obtained by a conventional method such as a roll coater method or a dry film laminating method. It was almost the same as the measured value.

Further, according to the method of this embodiment, since the laminated body 5 having the adhesive layer 14 as the outermost layer is formed by one heating and pressing step, the number of manufacturing steps is reduced and the manufacturing cost is reduced. It became a result.

The present invention is not limited to the first and second embodiments described above, but can be modified as follows. For example, (a) a laminated body is manufactured by impregnating a glass cloth (having a thickness of about 150 μm) with an adhesive varnish for additive to form a prepreg, and integrating the obtained adhesive-impregnated prepreg and an inner layer substrate. May be. Even with this method, it is possible to achieve the same effects as those of the first and second embodiments.

(B) The means for performing the heating / pressing is not necessarily limited to the autoclave 8 as in Embodiments 1 and 2, and, of course, may be replaced by another means capable of performing the isotropic pressing. It is possible to

(C) Further, even a uniaxial press such as a hot press can be used as a matter of course when the press pressure can be set low. At this time, it is possible to use a rubber filler or the like instead of the epoxy filler which is difficult to be crushed even when a high pressing pressure is applied.

(D) It is also possible to form a primary anchor and a secondary anchor in the roughened adhesive layer by using an adhesive in which fillers having different particle diameters are mixed in the matrix.

(E) The inner layer substrate 1 is not limited to the double-sided plates as in the first and second embodiments, but may be, for example, a four-layer plate or the like. Further, the manufacturing method of the inner layer substrate 1 is not limited to the subtractive method as shown in the first and second embodiments.

(F) It is of course possible to use an adhesive for additive which contains a catalyst nucleus in advance.

[0039]

As described in detail above, according to the method for manufacturing a multilayer printed wiring board of the present invention, a multilayer printed wiring board can be manufactured at a low cost despite forming the outermost conductor circuit by the additive method. It has an excellent effect that it can.

[Brief description of drawings]

FIG. 1 is a partially enlarged schematic front cross-sectional view showing an order in which an inner layer substrate, a prepreg, and an adhesive film are stacked in Example 1.

FIG. 2 is a partially enlarged schematic front cross-sectional view showing an order in which an inner layer substrate, a prepreg, an adhesive film, a release sheet and a mirror surface plate are superposed.

FIG. 3 is a schematic explanatory view showing a heating and pressing step by an autoclave.

FIG. 4 is a partially enlarged schematic front cross-sectional view showing an order in which an inner layer substrate, a prepreg having an adhesive layer formed thereon, a release sheet and a mirror surface plate are superposed in Example 2.

FIG. 5 is a partially enlarged schematic front cross-sectional view for explaining a conventional manufacturing process of a multilayer printed wiring board.

FIG. 6 is a partially enlarged schematic front cross-sectional view showing a laminated body obtained by integrating an inner layer substrate and a prepreg.

FIG. 7 is a partially enlarged schematic front cross-sectional view for explaining the manufacturing process of the conventional multilayer printed wiring board.

[Explanation of symbols]

1 ... inner layer substrate, 2 ... prepreg, 13, 14 ... adhesive layer,
3 ... Adhesive for film additive, 5 ... Laminated body.

Claims (2)

[Claims] 1. A prepreg is arranged on the outer side of an inner layer substrate, and a film-like additive for an adhesive serving as an adhesive layer is further arranged on the outer side of the inner prepreg to carry out heating and pressing, whereby the outermost layer is an adhesive layer. A method for manufacturing a multilayer printed wiring board, comprising: forming a laminated body having the adhesive layer, subjecting the adhesive layer to a roughening treatment, and then forming a conductor circuit on the outermost layer of the laminated body by an additive method. 2. An adhesive layer is preliminarily formed on one surface of a prepreg using a liquid additive adhesive, and the prepreg is laminated so that the adhesive layer-free surface side and the inner layer substrate side face each other. Then, a laminated body having an adhesive layer as an outermost layer is formed by heating and pressing, and then the adhesive layer is subjected to a roughening treatment, and then a conductor is formed on the outermost layer of the laminated body by an additive method. A method for manufacturing a multilayer printed wiring board, which comprises forming a circuit.