JP5593625B2 - Manufacturing method of multilayer wiring board - Google Patents

Description

The present invention relates to a method for manufacturing a multilayer wiring board , and more particularly to a method for manufacturing a multilayer wiring board having a structure in which conductor patterns arranged via a thermoplastic resin layer are connected via an interlayer connection conductor.

  In recent years, multilayer wiring boards in which wiring conductors are arranged three-dimensionally have been widely used for various applications. In the past, ceramic multilayer wiring boards having a structure in which a ceramic layer and a conductor pattern are laminated have been widely used. In recent years, multilayer wiring boards having a structure in which a thermoplastic resin layer and a conductor pattern are laminated are also used. Has come to be.

  By the way, in a multilayer wiring board using a thermoplastic resin, generally, a conductive paste containing metal particles and a binder is filled in a through hole for a via hole disposed in a thermoplastic resin layer which is an insulating layer. Thereafter, the interlayer connection of the conductor pattern is performed by heating while applying pressure.

  However, in the above conventional method, the interlayer connection of the conductor pattern is performed by contact conduction between the metal particles in the via hole through hole and contact conduction between the conductor pattern and the metal particle in the via hole through hole. A multilayer wiring board used under temperature conditions has a problem that the interlayer connection resistance value is likely to change.

  For example, in a high temperature environment, there is a problem that the contact resistance value between metal particles and the contact resistance value between the conductor pattern and the metal particles increase due to the expansion of the binder, and the reliability of the interlayer connection decreases.

  Therefore, as shown in FIGS. 5A and 5B, a conductive paste 54 containing Sn particles 52 and Ag particles 53 is filled in the through holes 51 for via holes, and a conductor pattern (Cu pattern) 55 is formed on the surface. A method of manufacturing a printed circuit board has been proposed in which an insulating base material (resin layer) 56 having an insulating layer is appropriately laminated and heated and pressed from both sides to perform interlayer connection (see Patent Document 1).

  According to this method, as shown in FIG. 5 (b), the Sn particles 52 are melted, alloyed with the Ag particles 53, and sintered to be integrated into a conductive composition 57. Since the Sn component and the conductor pattern (Cu pattern) 55 in the conductive composition 57 are solid-phase diffused to form the solid-phase diffusion layer 58, a plurality of conductor patterns 55 (the lower conductor pattern is shown in FIG. (Not shown) can be electrically connected to each other through a highly reliable joint that does not rely on contact conduction.

  However, in the case of this method, since the connecting portion of the Sn component in the conductive composition 57 and the conductor pattern (Cu pattern) 55 is performed via the solid phase diffusion layer 58, the contact area is small, and the insulating base material Due to the expansion and contraction of the (resin layer) 56, there is a problem that the solid phase diffusion layer 58 that is a connection portion is easily broken.

In addition, the solid phase diffusion layer 58 is generated at a low rate, and the hot press process at high temperature requires a long time, resulting in low productivity and high energy costs.
In addition, it is difficult to sufficiently diffuse in the hot pressing process, and there is a problem that the diffusion further progresses when exposed to high temperature during use of the product, and the connecting portion becomes brittle.

JP 2003-110243 A

The present invention solves the above-mentioned problem, and the conductor pattern disposed via the thermoplastic resin layer is securely connected via the interlayer connection conductor, and is excellent in connection reliability in the subsequent product stage. Another object of the present invention is to provide a method for manufacturing a multilayer wiring board capable of efficiently manufacturing the multilayer wiring board.

In order to solve the above problems, a method for manufacturing a multilayer wiring board of the present invention includes:
A multilayer having a structure in which a thermoplastic resin layer having a via-hole conductor disposed in a via-hole for a via hole and a patterned conductor layer are laminated, and the predetermined conductor layer is interlayer-connected through the via-hole conductor A method for manufacturing a wiring board, comprising:
A first base material layer is provided in which a patterned conductor layer is disposed on a surface of a thermoplastic resin layer in which a through hole for a via hole is formed so that a part thereof covers the through hole for a via hole. Process,
A second step of forming a coating metal layer on the back surface of the conductor layer and the inner bottom surface of the through hole for the via hole;
A third step of filling the through hole for via hole with a conductive paste having a conductive component of metal particles having a melting point higher than that of the metal material constituting the coating metal layer;
When the base material layer in which the conductive paste is filled in the via hole for the via hole in the third step is viewed as (a) the conductor layers to be connected to each other in the base material layers adjacent to each other. In such an embodiment, the covering metal layer disposed on the conductor layer of one base material layer is opposed to and in contact with the conductive paste filled in the through hole for the via hole of the other base material layer. And (b) higher than the melting point of the metal material constituting the coated metal layer formed in the second step, and higher than the melting point of the metal particles in the conductive paste filled in the via hole through hole. Laminating and pressing under low temperature conditions to form a diffusion layer between the metal particles in the conductive paste and the coating metal layer, and between the coating metal layer and the conductor layer, the diffusion Said conductive paste through a layer And a fourth step of electrically connecting the coated metal layer and the coated metal layer to the conductor layer.

  Further, in the present invention, the diffusion layers between the metal particles in the conductive paste and the coated metal layer and between the coated metal layer and the conductor layer may be formed by liquid phase diffusion. preferable.

  Moreover, in this invention, it is preferable in the said 2nd process that the said coating metal layer is formed in the whole exposed surface other than the joint surface with the said thermoplastic resin layer of the said conductor layer.

  Moreover, in the manufacturing method of the multilayer wiring board of this invention, it is preferable that the said electrically conductive paste is what has Ag particle | grains as a main component.

  The method for producing a multilayer wiring board according to the present invention comprises metal particles (conductor for interlayer connection) constituting conductive paste filled in via holes for via holes on the surface of the conductor layer and the back surface serving as the inner bottom surface of the via holes. The base layer obtained by forming a coating metal layer having a melting point lower than that of the via hole conductor and filling the through hole for via hole formed in the thermoplastic resin layer with a conductive paste is used as one base layer. Of the metal material constituting the coating metal layer in such a manner that the coating metal layer on the conductor layer faces and contacts the conductive paste filled in the through hole for via hole of the other adjacent base material layer. It is laminated under a temperature condition higher than the melting point and lower than the melting point of the metal particles in the conductive paste filled in the through-hole for via holes, and between the metal particles in the conductive paste and the coated metal layer and the coated gold Since a diffusion layer is formed between the conductive layer and the conductive layer, the metal particles in the conductive paste and the coated metal layer, and the coated metal layer and the conductive layer are electrically connected through the diffusion layer. In addition, the metal particles in the conductive paste and the covering metal layer, and the covering metal layer and the conductor layer can be electrically and reliably connected via the diffusion layer.

  In addition, as described above, since the steps of laminating and pressing are performed at a temperature higher than the melting point of the metal material constituting the coated metal layer, the metal particles in the conductive paste and the coated metal layer It is possible to form a diffusion layer by liquid phase diffusion between the cover metal layer and the conductor layer, and high connection reliability can be obtained.

  That is, in the present invention, the diffusion between the metal particles in the conductive paste and the coated metal layer and between the coated metal layer and the conductor layer can be liquid phase diffusion. Compared to the case of solid phase diffusion, a large contact area is ensured, and even when the thermoplastic resin layer expands or contracts, the diffusion layer that is the connection part is hard to break, realizing a highly reliable multilayer wiring board It becomes possible to do.

Further, in the case of liquid phase diffusion, the diffusion rate is faster than in the case of solid phase diffusion, and productivity can be improved.
In addition, since it is possible to sufficiently diffuse in the process of lamination and pressure bonding, even when exposed to high temperatures during use in the product stage, to suppress and prevent further diffusion, It is possible to provide a highly reliable multilayer wiring board in which the connecting portion does not become brittle.

  In addition, by forming the covering metal layer on the entire exposed surface of the conductor layer, it becomes the same state as the formation of the oxidation plating film on the surface of the conductor layer, suppressing the oxidation of the surface of the conductor layer, It is possible to improve connection reliability. In addition, in order to prevent the conductor layer from being oxidized, it is not necessary to provide a separate plating step, and productivity can be improved.

(a) is a figure which shows typically the structure of the multilayer wiring board manufactured by the method concerning the Example of this invention, (b) is the figure which expands and shows the principal part. (a), (b), (c) is a figure explaining the manufacturing method of the multilayer wiring board of FIG. (a), (b) is a figure explaining the manufacturing method of the multilayer wiring board of FIG. 1, Comprising: It is a figure which shows the process after the process of FIG.2 (c). It is a figure explaining the manufacturing method of the multilayer wiring board of FIG. 1, Comprising: It is a figure which shows the process following the process of FIG.3 (b). (a), (b) is a figure explaining the manufacturing method of the conventional multilayer wiring board.

  Examples of the present invention will be described below to describe the features of the present invention in more detail.

1A and 1B schematically show the structure of a multilayer wiring board manufactured by a method according to an embodiment of the present invention, where FIG. 1A is a front sectional view and FIG. It is an expanded sectional view.

  As shown in FIGS. 1 (a) and 1 (b), this multilayer wiring board 10 includes a thermoplastic resin layer 1 constituting a base material layer and a predetermined pattern disposed on the surface of the thermoplastic resin layer 1. And a via-hole conductor 4 filled and disposed in the via-hole through-hole 3 disposed in the thermoplastic resin layer 1 and connecting the conductor layer 2 to each other.

  In addition, a covering metal layer 5 is interposed in a connecting portion where the conductor layer 2 and the via hole conductor 4 face each other and contact each other, and between the via hole conductor 4 and the covering metal layer 5 and between the covering metal layer 5 and the conductor layer 2. A diffusion layer 6 is formed between them.

  In the multilayer wiring board 10, the thermoplastic resin layer 1 is formed of a thermoplastic resin having a melting point of 250 ° C. or higher, such as liquid crystal polymer (LCP) or polyether ether ketone (PEEK).

  The conductor layer 2 is formed by etching and patterning a copper foil formed on the surface of the thermoplastic resin layer 1.

The via-hole conductor 4 is formed by filling and baking the via-hole through hole 3 with a conductive paste containing Ag as a main component.
Furthermore, the covering metal layer 5 is formed of a Sn plating film.

Therefore, in this multilayer wiring board 10, the melting point (962 ° C.) of the via-hole conductor 4 made of Ag is higher than the melting point (232 ° C.) of the coated metal layer 5 made of Sn.
The melting point of Cu constituting the conductor layer (conductor pattern) 2 is 1083 ° C.

As will be described later, the multilayer wiring board 10 has a melting point higher than the melting point of the metal material constituting the coated metal layer 5 and is made of metal particles (Ag particles) in the conductive paste filled in the through holes 3 for via holes. Manufactured through a process of laminating and pressing under a temperature condition lower than the melting point. In the process of laminating and pressing, Sn constituting the coated metal layer 5 is melted, and the conductive paste is solidified and integrated. The diffusion layer 6 formed between the via-hole conductor 4 and the covering metal layer 5 and between the covering metal layer 5 and the conductor layer 2 is formed by liquid phase diffusion.

Therefore, in this multilayer wiring board 10, since the diffusion layer 6 between the via-hole conductor 4 and the coating metal layer 5 and between the coating metal layer 5 and the conductor layer 2 is formed by liquid phase diffusion, it is solid. Compared to the case of phase diffusion, a large contact area between the diffusion layer 6 and the via-hole conductor 4 and the conductor layer 5 is ensured, and even when the thermoplastic resin layer 1 expands or contracts, the diffusion layer 6 which is a connection portion. Is less likely to be destroyed and a highly reliable connection can be realized.

Hereinafter, a method for manufacturing the multilayer wiring board 10 will be described.
(1) First, as shown in FIG. 2 (a), an insulating layer made of a thermoplastic resin having a melting point of 250 ° C. or higher represented by liquid crystal polymer (LCP), polyether ether ketone (PEEK), etc. A sheet in which a metal foil (Cu foil in this embodiment) 2a formed by a rolling method is attached to the plastic resin layer 1 is prepared. In addition, the surface (back surface) joined to the thermoplastic resin layer 1 of Cu foil 2a is roughened, and the adhesive force with the thermoplastic resin layer 1 is improved.

(2) Then, as shown in FIG. 2 (b), the conductor layer (Cu foil) 2a on the thermoplastic resin layer 1 is etched to form a conductor pattern 2 having a desired pattern. For example, a predetermined resist pattern is formed on the surface of the conductor layer 2a, immersed in an etching solution and etched, and then the resist pattern is removed to obtain a desired conductor pattern as shown in FIG. 2 can be formed.
However, a pre-patterned Cu foil may be pasted.

  (3) Next, as shown in FIG. 2 (c), via-holes 3 for via holes are formed at predetermined positions of the thermoplastic resin layer 1 by laser processing. In the laser processing, the via hole through-hole 3 is formed so as to reach the back surface of the conductor pattern (conductor layer) 2 by irradiating the laser from the surface where the conductor pattern (conductor layer) 2 is not formed. . Thus, a patterned conductor layer (conductor pattern) 2 is disposed on the surface of the thermoplastic resin layer 1 in which the via hole through hole 3 is formed so that a part of the conductor layer covers the via hole through hole 3. The base material layer A having the above structure is obtained.

  The procedure for forming the base material layer A shown in FIG. 2 (c) is not limited to the procedures (1) to (3) described above. For example, the via hole 3 for the via hole is formed in the thermoplastic resin layer 1. After forming, the conductor layer 2a may be etched, or may be formed by another procedure.

  (4) Then, the conductor pattern 2 and the thermoplastic resin layer 1 (base material layer A) provided with the through holes 3 for via holes are immersed in a Sn plating bath, and as shown in FIG. A covering metal layer (Sn layer) 5 is formed on the entire exposed surface (that is, the surface 12a, the end surface 12b of the conductor pattern 2 and the back surface 12c serving as the inner bottom surface of the through hole 3 for via holes).

  (5) Next, as shown in FIG. 3 (b), each thermoplastic resin layer 1 (base material layer A) is filled with a conductive paste 4a mainly composed of Ag particles in the through holes 3 for via holes. To do.

  (6) Then, as shown in FIG. 4, each thermoplastic resin layer 1 (base material layer A) is laminated in a predetermined order, and the temperature at which the thermoplastic resin layer 1 exhibits plasticity but does not melt by vacuum pressing ( For example, pressure bonding is performed at 250 ° C. to 350 ° C. The uppermost layer in FIG. 4 is a thermoplastic resin layer (base material layer) A having the structure shown in FIG. 3B, but the second and third base materials from the top are conductor layers ( A thermoplastic resin layer (base material layer) A in which the shape of the conductor pattern) 2 and the arrangement position of the through hole 3 for via holes is different from that of the uppermost layer is used.

In this step, the covering metal layer (Sn layer) 5 is melted, so that the via hole conductor 4 made of Ag and the covering metal layer (Sn layer) 5 and the conductor pattern (conductor layer) 2 made of Cu and the covering are covered. Interdiffusion occurs between the metal layers (Sn layers) 5, and the via-hole conductor 4 and the conductor pattern (conductor layer) 2 are firmly bonded via the diffusion layer 6 (and the covering metal layer 5), and each heat The pressure bonding (bonding) between the plastic resin layers 1 is also completed, and the whole is completely integrated.
In this process, interdiffusion proceeds between the coated metal layer 5 and the via-hole conductor 4 and between the conductor pattern 2 and the coated metal layer 5, and at least part of the coated metal layer as the Sn single layer is lost. Sometimes it is.

  As a result, the highly reliable multilayer wiring board 10 in which the interface between the conductor pattern (conductor layer) 2 and the via-hole conductor 4 to which the greatest stress is applied during thermal expansion is joined via the diffusion layer (melting diffusion layer) 6. (FIG. 1) is obtained.

  In the above embodiment, the Sn layer is formed as the covering metal layer 5, but instead of the Sn layer, there is a rust prevention effect and the melting point is lower than the temperature when the thermoplastic resin layer 1 is pressure-bonded. Zn or the like can also be used.

  Moreover, in the said Example, although the coating metal layer 5 is formed by the plating method, the coating metal layer 5 can also be formed by thin film formation methods, such as a sputtering and CVD.

In the multilayer wiring board 10, the exposed conductor pattern (conductor layer) 2 is covered with the covering metal layer (Sn layer) 5, so that the exposed conductor pattern (conductor layer) 2 is oxidized. This can be suppressed or prevented. Therefore, a step of performing plating for the purpose of preventing oxidation after lamination can be eliminated.

  Further, the conductor pattern (conductor layer) 2 and the via-hole conductor 4 are quickly and reliably joined by the melt diffusion layer formed when the thermoplastic resin layer 1 (base material layer A) is laminated and pressed. Therefore, productivity can be greatly improved as compared with the case where bonding is performed via a diffusion layer by conventional solid phase diffusion (slow diffusion).

  Furthermore, since the diffusion layer 6 formed at the bonding interface is a diffusion layer formed by liquid phase diffusion, the stress due to the difference in thermal expansion / contraction rate between the thermoplastic resin layer 1 and the conductor pattern (conductor layer) 2 is reduced. Since the connection resistance is low and strong, the highly reliable multilayer wiring board 10 can be provided.

  In other respects, the present invention is not limited to the above-described embodiments, and the type of material constituting the thermoplastic resin layer, the type of material constituting the conductor layer (conductor pattern), and the specifics of the conductor layer. Various applications and modifications can be made within the scope of the present invention with respect to the number of laminated patterns and lamination modes of a typical pattern, a thermoplastic resin layer, and a conductor layer.

According to the present invention, a conductor layer (conductor pattern) disposed via a thermoplastic resin layer is securely connected via a via-hole conductor, and a subsequent multilayer wiring board with high connection reliability is efficiently manufactured. It becomes possible to do.
Therefore, the present invention can be widely applied to a technical field related to a multilayer wiring board and its manufacture.

1 Thermoplastic resin layer 2 Conductor pattern (conductor layer)
2a Conductor layer before patterning 3 Via hole for via hole 4 Via hole conductor (Ag)
4a Conductive paste 5 Coated metal layer (Sn layer)
6 diffusion layer 10 multilayer wiring board 12a surface of conductor pattern 12b end surface of conductor pattern 12c back surface of conductor pattern A base material layer

Claims (4)

A multilayer having a structure in which a thermoplastic resin layer having a via-hole conductor disposed in a via-hole for a via hole and a patterned conductor layer are laminated, and the predetermined conductor layer is interlayer-connected through the via-hole conductor A method for manufacturing a wiring board, comprising:
A first base material layer is provided in which a patterned conductor layer is disposed on a surface of a thermoplastic resin layer in which a through hole for a via hole is formed so that a part thereof covers the through hole for a via hole. Process,
A second step of forming a coating metal layer on the back surface of the conductor layer and the inner bottom surface of the through hole for the via hole;
A third step of filling the through hole for via hole with a conductive paste having a conductive component of metal particles having a melting point higher than that of the metal material constituting the coating metal layer;
When the base material layer in which the conductive paste is filled in the via hole for the via hole in the third step is viewed as (a) the conductor layers to be connected to each other in the base material layers adjacent to each other. In such an embodiment, the covering metal layer disposed on the conductor layer of one base material layer is opposed to and in contact with the conductive paste filled in the through hole for the via hole of the other base material layer. And (b) higher than the melting point of the metal material constituting the coated metal layer formed in the second step, and higher than the melting point of the metal particles in the conductive paste filled in the via hole through hole. Laminating and pressing under low temperature conditions to form a diffusion layer between the metal particles in the conductive paste and the coating metal layer, and between the coating metal layer and the conductor layer, the diffusion Said conductive paste through a layer And a fourth step of electrically connecting the coated metal layer and the coated metal layer to the conductor layer. A method for producing a multilayer wiring board, comprising:   2. The diffusion layer between the metal particles and the coated metal layer in the conductive paste and between the coated metal layer and the conductor layer is formed by liquid phase diffusion. Manufacturing method of multilayer wiring board.   3. The multilayer wiring board according to claim 1, wherein, in the second step, the covering metal layer is formed on the entire exposed surface of the conductor layer other than the bonding surface with the thermoplastic resin layer. Production method.   The method for manufacturing a multilayer wiring board according to claim 1, wherein the conductive paste is mainly composed of Ag particles.

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