JP2001028481A - Multi-layer wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layer wiring board of very small thermal-expansion factor, high connection reliability, and high freeness in wiring, SOLUTION: A plurality of both-sided circuit boards 1 are provided where circuit 4 is provided on both surfaces of an insulating layer 3 of organic polymer resin whose base body is an alloy foil 2, with both circuits 4 electrically connected using a via filled with a conductive paste 5a. The plurality of both-sided circuit boards 1 are integrally laminated, through an adhesive layer 6. Related to the adhesive layer 6, a hole is opened at specified positions which contact the circuits 4 of two both-sided circuit boards 1 sandwiching it. The opened hole is provided with a solder conductor 7, which electrically connects the circuits 4 of the two both-sided circuit boards 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multilayer wiring board and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the recent trend toward miniaturization and high performance of electronic devices, semiconductor devices constituting the electronic devices and multilayer wiring boards on which the electronic devices are mounted are required to be small, thin, high performance, and high reliability. Have been. In response to these demands, the mounting method has shifted from a pin insertion type package to a surface mount type package. Recently, a mounting method called bare chip mounting, in which a semiconductor element is directly mounted on a printed circuit board, has been studied. Further, with the increase in the number of pins of the semiconductor element, the necessity of increasing the number of layers of the substrate on which the semiconductor element is mounted is increasing. As a method of multi-layering, a built-up type multilayer wiring board has been proposed in which an insulating layer using a photosensitive resin and a conductor layer formed by plating or vapor deposition are alternately stacked on one or both sides of a base. However, in this case, there are problems that the manufacturing process is complicated and the number of processes is large, and that the yield is low and the delivery time is long. Alternatively, a method of forming a conductive paste on one surface (copper-coated surface) of a glass epoxy single-sided copper-clad laminate as a projection using a dispenser or the like, stacking an adhesive sheet and a copper foil, applying pressure, and repeating the process to form a multilayer structure. It has been proposed (Japanese Patent Laid-Open No. 8-28
No. 8649). However, this method has problems in connection reliability, connection resistance, and the like, and is difficult to apply to fine circuits. Further, in order to increase the number of layers, it is necessary to repeat pressing for the number of layers. There were various problems such as a long time for manufacturing.

On the other hand, in the bare chip mounting, the thermal expansion coefficient:
A silicon chip of 3 to 4 ppm / ° C. has a coefficient of thermal expansion of 10
Since the printed circuit board is directly bonded to the printed board at ２０20 ppm / ° C. via an adhesive, a stress is applied due to a difference in thermal expansion between the two, causing a problem that connection reliability is reduced. In addition, the above-mentioned stress also causes problems such as causing cracks in the adhesive and reducing moisture resistance. In order to alleviate such stress, a method of lowering the elastic modulus of the adhesive to achieve the effect of diffusing the stress has been carried out. However, even with these methods, sufficient connection reliability can be ensured. In order to ensure even higher connection reliability, it is essential to lower the thermal expansion coefficient of the base itself.

Against this background, the present invention provides wiring conductors on both surfaces of an insulating layer made of an organic polymer resin having a metal core as a base, and electrically connects these wiring conductors on both front and back surfaces with through holes. A multilayer wiring board in which a plurality of low-thermal-expansion double-sided circuit boards are prepared, and these double-sided circuit boards are laminated and integrated via an adhesive layer, and a method for manufacturing the same are proposed (Japanese Patent Application No. 9-260201). ).

[0005]

However, in a plurality of double-sided circuit boards constituting the above-mentioned multilayer wiring board, through holes for electrically connecting the wiring conductors on the front and back surfaces of the circuit board are not used in an environmental acceleration test such as a temperature cycle test. There is a problem in reliability such as cracks generated in the inside of the through hole or the corner of the through hole. Therefore, it is conceivable to improve the reliability by increasing the plating thickness of the through hole, but in this case, fine wiring cannot be provided in a circuit forming process by etching. On the other hand, in order to form fine wiring, it is necessary to reduce the thickness of the conductor layers on both the front and back surfaces, but the reliability of the through holes is reduced. Further, in the step of laminating and integrating the plurality of double-sided circuit boards via the adhesive layer, it is necessary to electrically connect the wiring conductors of the two (both vertically adjacent) stacked two-sided circuit boards with a conductor made of solder. However, since a conductor made of solder cannot be provided on the through hole of the double-sided circuit board, the degree of freedom of wiring is greatly impaired.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a multilayer wiring board having a very low coefficient of thermal expansion, high connection reliability, and a high degree of freedom in wiring, and a method of manufacturing the same. Aim.

[0007]

In order to achieve the above-mentioned object, the present invention provides an insulating layer made of an organic polymer resin having a metal core as a base, and wiring conductors are provided on both surfaces of the insulating layer. A plurality of double-sided circuit boards electrically connected by via holes filled with a conductive resin are laminated and integrated via an adhesive layer, and the adhesive layer has wiring conductors of two double-sided circuit boards sandwiching the same. A hole is formed at a predetermined position of a portion in contact with the substrate, a conductor made of solder is provided in the hole, and a wiring conductor of the two double-sided circuit boards is electrically connected by the conductor made of solder. A method of manufacturing a multilayer wiring board having a wiring board according to a first aspect, wherein wiring conductors are provided on both surfaces of an insulating layer made of an organic polymer resin having a metal core as a base, and both of the wiring conductors are hardened conductive layers. Resin A step of preparing a plurality of double-sided circuit boards electrically connected by the filled via holes and an adhesive sheet opened at a position corresponding to a predetermined portion of the wiring conductor of the double-sided circuit board; Temporarily bonding the adhesive sheet to the double-sided circuit board in a state where the opening of the adhesive sheet is aligned with a predetermined portion of the provided wiring conductor, and printing the opening of each adhesive sheet after the adhesive sheet is temporarily bonded. Filling the solder paste and heating and melting to form solder bumps, and stacking and heating each of the double-sided circuit boards by aligning the wiring conductors of each of the double-sided circuit boards after the formation of the solder bumps so that predetermined electrical connections can be made. A second feature of the present invention is a method for manufacturing a multilayer wiring board including a step of integrating the whole by pressing.

That is, the present inventors have conducted a series of studies to obtain a multilayer wiring board having a very low coefficient of thermal expansion, high connection reliability, and high wiring flexibility. And when the wiring conductors on both sides are electrically connected by via holes filled with curable conductive resin, the coefficient of thermal expansion is extremely small, and the connection reliability is high and the wiring flexibility is large. Have been found, and the present invention has been achieved. As in the multilayer wiring board of the present invention, a low thermal expansion double-sided circuit board can be obtained by using a metal core as a base, and a low thermal expansion multilayer wiring board can be obtained by laminating and integrating these in multiple layers. . Also, when a via hole filled with a curable conductive resin is provided instead of providing a through hole as in the multilayer wiring board of the present invention, cracks occur inside and at corners even in an environmental acceleration test such as a temperature cycle test. And high connection reliability. Further, by providing a conductor made of solder on the via hole filled with the curable conductive resin, it is possible to electrically connect the wiring conductors of the two double-sided circuit boards that are stacked (adjacent vertically), so that the wiring is free. Great degree. Further, since the metal core disposed as a base on each double-sided circuit board has a very low coefficient of thermal expansion not only in the XY directions but also in the Z direction, it suppresses dimensional changes of via holes in an environmental acceleration test such as a temperature cycle test. There is an effect, and connection reliability can be improved.

On the other hand, in the manufacturing method of the present invention, the adhesive sheet is aligned and temporarily bonded to the double-sided circuit board, and solder bumps are formed in the openings formed in the adhesive sheet. Since the whole is integrated and stacked and heated and pressed, a plurality of double-sided circuit boards can be integrated by one heating and pressing. At the same time, regardless of the number of layers of the wiring conductor, electrical connection between the wiring conductors can be performed by the single heating and pressing. In the present invention, "preparing an adhesive sheet that is opened at a position corresponding to a predetermined portion of a wiring conductor of a double-sided circuit board" means that the adhesive sheet is placed on a double-sided circuit board and then opened. is there.

Next, the present invention will be described in detail.

In the double-sided circuit board constituting the multilayer wiring board of the present invention, a polyimide adhesive is preferably used as the organic polymer material used as the insulating layer.
The present invention is not limited to this, and polyetherimide, polyethersulfone, epoxy, and the like are used. Further, as a metal material forming the wiring conductors on both the front and back surfaces of the insulating layer, copper is preferably used, but not limited thereto, and gold, silver or the like is used.

As a means for forming a via hole (through hole) in the insulating layer, an appropriate method may be selected according to the size of the hole, and examples thereof include a drill, a punch, and a laser. As the curable conductive resin to be filled in the through hole, a conductive material such as Ag, Cu, Au, Ni, Pb, Sn, C, and an epoxy resin, a phenol resin, a polyimide resin, and the like, together with an organic agent as necessary. A well-known curable conductive resin mixed into a paste can be used.

In filling the through-hole with the curable conductive resin, the curable conductive resin may be filled so as to fill the entire space of the through-hole. As a typical filling method of the curable conductive resin, for example, a printing method is used.
A method of applying once or a plurality of times, a method of press-fitting with a pair of front and back squeegees from both front and back sides of the double-sided board,
A method of filling with a roll coater or a curtain coater and scraping an excessive amount with a squeegee is suitably used. The curing of the curable conductive resin filled in the through holes is performed by a hot air oven, infrared oven, far-infrared oven, ultraviolet curing oven,
What is necessary is just to select what is suitable for hardening of a hardening type conductive resin by well-known hardening methods, such as an electron beam hardening furnace.

To form a circuit on a double-sided board in which the through-hole is filled with a curable conductive resin, a through-hole is provided in advance in an adhesive layer, and the through-hole is filled with the curable conductive resin. It is obtained by laminating copper foil on both sides of the layer and then performing patterning. The thickness of the circuit layer is 3
It is set to 6 μm or less, preferably 18 μm or less. Above this range, it is difficult to miniaturize circuit wiring.

Core materials used for realizing low thermal expansion of the substrate include Fe, Ni, Cr, Al, Ti, and C.
u, Co or an alloy foil containing them, or a ceramic material is used. Since the metal foil or the ceramic material functions to suppress the expansion of the conductor layer and the insulating layer, the coefficient of thermal expansion of the metal foil or the ceramic material itself needs to be sufficiently small. When the core material is a Ni—Fe alloy foil, since the coefficient of thermal expansion changes depending on the ratio, the Ni content (% by weight) is 31%.
The range of 50 to 50% by weight, preferably 31 to 45% by weight is suitably used. If it is above or below this range,
The coefficient of thermal expansion is large, and the same coefficient of thermal expansion as the chip cannot be obtained. The thickness of the metal foil is 10 to 300 μm.
m, preferably 10 to 200 μm, more preferably 10 to 100 μm. If the thickness is smaller than this, the difference in thermal expansion between the circuit board and the silicon chip cannot be suppressed. The ratio of the thickness of the metal foil to the total thickness of the metal foil and the insulating layer is 10 to 95%, preferably 30 to 95%. If less than this percentage,
During the temperature cycle test, there is a problem that the dimensional change of the via hole cannot be sufficiently suppressed. If the size is large, there is a problem that the insulation resistance value between the circuit layer and the metal core increases in the migration test.

In order to make the double-sided circuit board multi-layered, an adhesive sheet perforated at a position corresponding to a required position of the double-sided circuit board is aligned and temporarily bonded to both sides or one side of the double-sided circuit board. It can be realized by putting a solder paste into the opening by printing, heating and melting the double-sided circuit board with solder bumps on which solder bumps are formed, aligning a plurality of the double-sided circuit boards, and applying heat and pressure to integrate them. Here, the opening may be applied to a circuit on a via that electrically connects wiring conductors on both front and back surfaces of a double-sided circuit substrate.

Since the above-mentioned adhesive sheet becomes an insulating layer after lamination and integration, the adhesive constituting the adhesive sheet is preferably a polyimide type, an epoxy type or a mixture type thereof from the viewpoint of heat resistance, electric characteristics and the like. As the thickness of the adhesive sheet,
It is preferable that the thickness be about 0.01 mm to 1.0 mm. If it is smaller than this range, workability is poor. If the amount is more than this range, the solder paste is not filled into the opening portion well, which causes a decrease in reliability. As a means for forming a hole in the adhesive sheet, an appropriate method may be selected according to the size of the hole, and examples thereof include a drill, a punch, and a laser.

In the step of temporarily fixing the adhesive sheet, the opened adhesive sheet may be temporarily bonded to an arbitrary position on both sides or one side of the low thermal expansion double-sided circuit board by using a hot press. Alternatively, the adhesive sheet may be preliminarily bonded to both sides or one side of the double-sided circuit board, and then the holes may be opened using a laser. As a laser, carbon dioxide,
Excimer, YAG and the like are preferably used.

In forming the solder bumps, a commercially available solder paste is used.
The size of the solder particles is 100 μm or less, preferably 50 μm.
m or less, more preferably 10 μm or less.
The solder composition is not particularly limited, and may be selected according to the heat resistance required for the substrate. The solder bumps after the lamination are brought into contact with the opposite electrodes and become conductive, but if necessary, the substrate may be heated to a temperature higher than the melting point of the solder for metal bonding. This metal bonding method may be performed simultaneously with the integration of the substrates by heating and pressing, or may be performed again after the integration.

[0020]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the multilayer wiring board of the present invention. In FIG. 1, reference numeral 1 denotes a double-sided circuit board in which a circuit (wiring conductor) 4 made of a copper foil is formed on both front and back surfaces of an insulating layer 3 made of a polyimide resin having a Ni-Fe alloy foil 2 as a base. In this embodiment, three double-sided circuit boards 1 are used, whereby a six-layer wiring board is manufactured as a multilayer wiring board. Reference numeral 5 denotes a via formed by filling a through-hole (via hole) 1a formed in each of the double-sided circuit boards 1 with a conductive paste 5a, and electrically connects the circuits 4 on both front and back sides. The conductive paste 5a has a mean particle size of 5 μm as a conductive filler.
The spherical copper powder was mixed with a thermosetting epoxy resin as a resin and an acid anhydride-based curing agent as a curing agent. Reference numeral 6 denotes a polyimide adhesive layer for bonding the two-sided circuit boards 1 to each other. Reference numeral 7 denotes a conductor made of solder for electrically connecting the circuits 4 of the two double-sided circuit boards 1 stacked (adjacent to each other).

The double-sided circuit board 1 can be manufactured as follows. That is, first, as shown in FIG. 2, a hole 2 a is opened at a predetermined position of the Ni—Fe alloy foil 2 (a position where a via 5 filling the conductor 5 a made of solder) is provided.
Then, a polyimide-based adhesive sheet 11 (which will be an insulating layer 3 of the base material 8 described later) is attached to the front and back surfaces of the Ni-Fe-based alloy foil 2 to produce the base material 8 as shown in FIG. Next, as shown in FIG.
In the portion corresponding to the opening 2a of the e-based alloy foil 2, a through hole 1a smaller than the opening 2a is opened. Next, as shown in FIG. 5, after filling the through-hole 1a with the conductive paste 5a, the conductor layers 4a made of copper foil are bonded from both the front and back surfaces to electrically connect the conductor layers 4a on both front and back surfaces. (See FIG. 6). Since the coefficient of thermal expansion of the base material 9 thus obtained is governed by the Ni—Fe-based alloy as the material of the core material, the coefficient of thermal expansion can be changed by changing the ratio of Ni—Fe and the thickness of the foil. Can be adjusted.
Next, the circuit 4 is formed on the conductor layers 4a on both the front and back surfaces of the base material 9 shown in FIG. 6 to produce the double-sided circuit board 1 (see FIG. 7).

The above multilayer wiring board can be manufactured as follows. That is, first, three double-sided circuit boards 1 (see FIG. 7) in which a circuit 4 made of copper foil is formed on both sides of an insulating layer 3 made of a polyimide resin, and two adhesive sheets made of a polyimide-based adhesive (See FIG. 8)
Prepare 3 and 3. Next, as shown in FIG. 9, each of the adhesive sheets 13 is attached to two (of three) double-sided circuit boards 1.
The opening 13a of each adhesive sheet 13 is aligned with a predetermined position of the circuit 4 of each double-sided circuit board 1 (the position where the solder conductor 7 in FIG. 1 is provided) and temporarily bonded. Next, as shown in FIG.
a, solder paste is applied to the circuit 4 of each double-sided circuit board 1 by heating and melting.
To form Next, two double-sided circuit boards 1 on which the solder bumps 14 are provided and one double-sided circuit board 1 on which only the circuit 4 is formed are aligned with each other, and a plurality of the double-sided circuit boards 1 are stacked (see FIG. 11). Press and integrate. In this state, each adhesive sheet 13 becomes the adhesive layer 6, and each solder bump 14 becomes the conductor 7 made of solder. As a result, a six-layer wiring board in which three double-sided circuit boards 1 are laminated and integrated can be obtained.

As described above, in this embodiment, the three double-sided circuit boards 1 can be integrated by one heating and pressurization, and at the same time, the electrical connection between the six layers can be performed. Moreover, 2
Since the Ni—Fe-based alloy foil 2 is disposed at a ratio of one layer to the circuit 4 of the layer, even when the circuit 4 is formed of copper foil, the thermal expansion coefficient of the entire six-layer wiring board is reduced. The connection reliability can be reduced, and extremely high connection reliability can be obtained. Also,
In the electrical connection of the six layers (electrical connection between the six layers), the conductors 5a and 7 are used, so that the connection resistance is low,
A highly reliable connection can be made. Furthermore, each conductor 7 made of solder
Can be arranged at any position without being affected by the conductive paste 5a of the via 5, so that the degree of freedom in design is increased and high-density wiring can be realized.

Hereinafter, the effects of the present invention will be described with reference to examples.

[0026]

Example: 300 mm at a predetermined position with a punch having a diameter of 150 μm.
36 holes of 50μm thickness with holes 2a opened at μm pitch
A foil 2 (Ni: 36% by weight, Fe: 64% by weight, thermal expansion
(Coefficient of 1.5 ppm / ° C)
Polyimide adhesive sheet 11 (manufactured by Nippon Steel Chemical: SPB
-035A) using pressure and heat bonding (40 kg / cm
^Two(200 ° C, 60 min) (see Fig. 2)
An expansion substrate 8 was produced (see FIG. 3). Next, 36 alo
A punch having a diameter of 100 μm is placed at the same position as the hole 2 a of the foil 2.
Using this, a through-hole 1a was opened (see FIG. 4). The through hole 1
a Fill the top with conductive paste by screen printing
After curing (175 ° C, 60min)
A via 5 was provided (see FIG. 5). At this time, the conductive pace
Is spherical copper with an average particle size of 5 μm as a conductive filler
Powder, thermosetting epoxy resin as resin, curing agent
85% by weight of acid anhydride-based curing agent
% And 2.5% by weight.
Was. Next, a thickness of 1 on both surfaces of the low thermal expansion substrate 8.
8μm copper foil 4a is bonded under pressure and heat (40kg / cm ^Two,
(200 ° C., 60 min) (see FIG. 6).
The circuit 4 is applied to the copper foil 4a on both sides by the conventional etching method.
Thus, a double-sided circuit board 1 was manufactured (see FIG. 7).

A polyimide adhesive sheet 13 (manufactured by Nippon Steel Chemical Co., Ltd.) in which holes 13a are opened with a punch having a diameter of 150 μm on the low-thermal-expansion double-sided circuit board 1 manufactured by the above method.
SPB-035A) (see FIG. 8) was placed at a predetermined position, and in that state, heat and pressure bonding (20 kg / cm ² ,
(175 ° C., 30 min) (see FIG. 9). Next, the opening 13a of the adhesive sheet 13 was filled with a solder paste (manufactured by Tamura Kaken Corp .: SQ10-11) by screen printing.
After reflow at 220 ° C., the flux was washed away to form solder bumps 14 (see FIG. 10). In the same manner, another double-sided circuit board 1 with solder bumps 14
To manufacture a double-sided circuit board 1 which has been performed up to the formation of the circuit 4, these three substrates are aligned and stacked, and heated and pressed (50 kg /
cm ² at 175 ° C. for 60 minutes (FIG. 1)
1), and a six-layer wiring board was produced (see FIG. 1).

[0028]

Comparative Example 1 A punch having a diameter of 150 μm was placed at a predetermined position by 30
A 50 μm thick 36-alloy foil 2 (Ni: 36% by weight, Fe: 64% by weight, thermal expansion coefficient: 1.5 ppm / ° C.) having holes 2a formed at a pitch of 0 μm is formed on both the front and back surfaces by a thickness of 18 μm.
Pressure bonding by using a 35 μm-thick polyimide-based adhesive sheet (SPB-035A, manufactured by Nippon Steel Chemical Co., Ltd.) (which becomes the insulating layer 3 of the substrate 8 described below) under pressure and heat (40 kg)
/ Cm ² , 200 ° C., 60 min) and a low thermal expansion substrate 8
(See FIG. 12). Further, a through-hole 1a was opened at the same position as the hole 2a of the 36 alloy foil 2 using a punch having a diameter of 100 μm (see FIG. 13). Next, as shown in FIG. 14, through-hole plating of copper having a plating thickness of 10 μm is performed (through-hole plating portions 16 are formed), and a circuit 4 is formed on the copper foil 4a on both front and back surfaces by a conventional etching method. Thus, a double-sided circuit board 1 was produced (see FIG. 15).

After that, in the same manner as in the above embodiment, the adhesive sheet 13 is temporarily bonded, the solder bumps 14 are formed, the whole is integrated by heating and pressing, and the electrical connection between the layers is performed.
A low thermal expansion multilayer wiring board having a layer structure was manufactured.

[0030]

Comparative Example 2 A 35-μm-thick polyimide-based adhesive sheet 22 (SPB-035A, manufactured by Nippon Steel Chemical Co., Ltd.) was applied to both the front and back surfaces of an insulating layer 21 (thickness: 50 μm) made of polyimide resin under pressure and heat (40 kg / cm ²⁾ , 200 ° C, 5mi
n) A diameter of 100 μm at a predetermined position on the polyimide substrate
(See FIG. 16). Next, a conductive paste is filled in the upper portion of the through hole 23a by screen printing, and then cured (175 ° C., 60 mi).
n) was performed to provide conductive vias 24 (see FIG. 17).
At this time, the conductive paste was composed of spherical copper powder having an average particle size of 5 μm as a conductive filler, a thermosetting epoxy resin as a resin, and an acid anhydride-based curing agent as a curing agent at 85% by weight. What was mixed at the ratio of 2.5% by weight was used. Next, in the same manner as in the above example, a copper foil having a thickness of 18 μm was bonded by heating under pressure, a circuit 25 was formed, a double-sided circuit board 26 was produced (see FIG. 18), and an adhesive sheet 13 was temporarily bonded. Then, the solder bumps 14 were formed, and the whole was integrated by heating and pressurizing, and electrical connection between layers was performed, thereby producing a low thermal expansion multilayer wiring board having a six-layer structure.

Each of the vias 5, 24 in the six-layer wiring board described in the embodiment and the comparative examples 1 and 2 manufactured as described above.
Thermal shock test (liquid layer: -65 ° C ： 1)
(50 ° C., 5 min each). Table 1 below shows the number of cycles in which conduction failure occurred in each of the vias 5 and 24. Here, the case where the resistance value change is ± 10% or more is regarded as a conduction failure.

[0032]

[Table 1]

As apparent from Table 1 above, Comparative Example 1
In a (six-layer wiring board having a conventional through-hole structure), conduction failure occurs in 100 cycles or less. On the other hand, in the six-layer wiring board shown in the example, the change in the resistance value of each via 5 is maintained within ± 10% up to 800 cycles, and the electrical connection between the circuits 4 is made of the conductive paste 5a.
It is clear that the connection reliability of the six-layered wiring board performed by the vias 5 and 24 filled with is high. Further, a comparison between the example in which the electrical connection between the respective circuits 4 is made by the conductive vias 5 and the comparative example 2 shows that Ni was used as the core material.
The reliability is greatly improved by using the Fe-based alloy foil 2. It is considered that the Ni-Fe-based alloy foil 2 suppressed the amount of deformation in the Z-axis direction around the via 5 and thus improved the reliability of the embodiment.

In the embodiment and the comparative example 2, since arbitrary layers can be freely connected by fine vias 5 and 24,
It is obvious that the degree of freedom in design is increased and high-density wiring can be easily realized.

Further, the insulating layer of the double-sided circuit board 1 contains a low thermal expansion core material made of a Ni--Fe alloy foil 2 in a ratio of one layer to the conductor layer 4a. When the coefficient of thermal expansion of the six-layer wiring boards described in Examples and Comparative Examples 1 and 2 was measured in a range from room temperature (25 ° C.) to 200 ° C.,
The results are shown in Table 2 below.

[0036]

[Table 2]

As shown in Table 2 above, N was used as the core material.
The thermal expansion coefficients of the six-layer wiring boards of the example and the comparative example 1 using the i-Fe-based alloy foil 2 are extremely small, and it is clear that the boards are suitable for bare chip mounting. in this way,
Needless to say, the low thermal expansion multilayer wiring board of the embodiment is a board having extremely high electrical connection reliability suitable for bare chip mounting.

[0038]

As described above, according to the multilayer wiring board of the present invention, when a via hole filled with a curable conductive resin is provided instead of providing a through hole, an environmental acceleration test such as a temperature cycle test can be performed. No cracks are formed inside or at the corners, and the connection reliability is high. In addition, since a conductor made of solder is provided on the via hole filled with the curable conductive resin and the wiring conductors of two adjacent (stacked) double-sided circuit boards can be electrically connected, the degree of freedom of wiring is increased. large. Further, since the metal core disposed as a base on each double-sided circuit board has a very low coefficient of thermal expansion not only in the XY directions but also in the Z direction, it suppresses dimensional changes of via holes in an environmental acceleration test such as a temperature cycle test. It is effective and improves connection reliability.

On the other hand, in the manufacturing method of the present invention, the adhesive sheet is aligned and temporarily bonded to the double-sided circuit board, solder bumps are formed in the openings formed in the adhesive sheet, and the double-sided circuit boards are aligned. Since the whole is integrated by heating and pressing, a plurality of double-sided circuit boards can be integrated by one heating and pressing. At the same time, regardless of the number of layers of the wiring conductor, electrical connection between the wiring conductors can be performed by the single heating and pressing. In the present invention,
“Preparing an adhesive sheet that is opened at a position corresponding to a predetermined portion of the wiring conductor of the double-sided circuit board” means that the adhesive sheet is placed on the double-sided circuit board and then opened.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a multilayer wiring board of the present invention.

FIG. 2 is a cross-sectional view illustrating a manufacturing process of the double-sided circuit board.

FIG. 3 is a sectional view showing a manufacturing process of the double-sided circuit board.

FIG. 4 is a cross-sectional view showing a manufacturing process of the double-sided circuit board.

FIG. 5 is a sectional view showing a manufacturing process of the double-sided circuit board.

FIG. 6 is a cross-sectional view showing a manufacturing process of the double-sided circuit board.

FIG. 7 is a sectional view of the double-sided circuit board.

FIG. 8 is a sectional view showing an adhesive sheet.

FIG. 9 is a cross-sectional view showing a state where an adhesive sheet is temporarily bonded to a double-sided circuit board.

FIG. 10 is a sectional view showing a state in which solder bumps are formed on an adhesive sheet.

FIG. 11 is a cross-sectional view showing a state in which respective double-sided circuit boards are stacked.

FIG. 12 is a cross-sectional view illustrating a manufacturing process of Comparative Example 1.

FIG. 13 is a cross-sectional view illustrating a manufacturing process of Comparative Example 1.

FIG. 14 is a cross-sectional view illustrating a manufacturing process of Comparative Example 1.

FIG. 15 is a cross-sectional view illustrating a manufacturing process of Comparative Example 1.

FIG. 16 is a cross-sectional view showing a manufacturing process of Comparative Example 2.

FIG. 17 is a cross-sectional view illustrating a manufacturing process of Comparative Example 2.

FIG. 18 is a cross-sectional view showing a manufacturing step of Comparative Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Double-sided circuit board 2 Alloy foil 3 Insulating layer 4 Circuit 5a Conductive paste 6 Adhesive layer 7 Solder conductor

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasushi Inoue 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Toku Nagasawa 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Takuji Okei 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 5E346 AA03 AA43 CC08 CC09 CC10 CC32 CC37 CC38 CC39 CC40 DD02 EE05 EE08 EE13 FF18 FF19 FF24 GG08 GG09 GG15 GG28 HH31

Claims (6)

[Claims] A plurality of wiring conductors are provided on both surfaces of an insulating layer made of an organic polymer resin having a metal core as a base, and both wiring conductors are electrically connected by via holes filled with a curable conductive resin. The double-sided circuit board is laminated and integrated via an adhesive layer, and a hole is formed in the adhesive layer at a predetermined position of a portion of the two double-sided circuit boards that abuts the wiring conductor and sandwiches the hole. A multi-layer wiring board, wherein a conductor made of solder is provided in a portion, and the wiring conductors of the two double-sided circuit boards are electrically connected by the conductor made of solder. 2. The method according to claim 1, wherein the curable conductive resin is Ag, Cu,
At least one selected from Au, Ni, Pb, Sn, C
The multilayer wiring board according to claim 1, wherein the multilayer wiring board includes a conductive material of a kind. 3. The method according to claim 2, wherein the metal core is Fe, Ni, Al,
2. The multilayer wiring board according to claim 1, which is a metal foil made of Ti, Cu, Co, or an alloy containing these. 4. The multilayer wiring board according to claim 1, wherein the metal core is a Ni—Fe alloy foil, the Ni content is 31 to 50% by weight, and the thickness is in a range of 10 μm to 100 μm. 5. The multilayer wiring board according to claim 1, wherein the ratio of the thickness of the metal core to the total thickness of the metal core and the insulating layer is 30 to 95%. 6. A method for manufacturing a multilayer wiring board according to claim 1, wherein wiring conductors are provided on both surfaces of an insulating layer made of an organic polymer resin having a metal core as a base, and both of the wiring conductors are hardened conductive layers. Preparing a plurality of double-sided circuit boards electrically connected by via holes filled with a conductive resin, and an adhesive sheet opened at a position corresponding to a predetermined portion of a wiring conductor of the double-sided circuit board; Temporarily bonding the adhesive sheet to the double-sided circuit board in a state where the opening of the adhesive sheet is aligned with a predetermined portion of the wiring conductor provided on the circuit board; Filling the solder paste by printing and heating and melting to form solder bumps, and aligning the wiring conductors on each of the double-sided circuit boards after the formation of the solder bumps so that predetermined electrical connections can be made. And a step of stacking the double-sided circuit boards, heating and pressurizing them to integrate them as a whole.