JP2003273517A - Multilayer circuit board and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer circuit board having high connection reliability in mounting components and to provide a method for manufacturing it. <P>SOLUTION: This multilayer circuit board 100 is formed with conductor layers 1 and 8 configuring wiring circuits on the both sides of an insulating layer 2. The respective wiring circuits formed on both sides are electrically connected through a via hole 2a where a solder conductor 9 diffused with metallic power 3 is packed, and an alloy formed of metal configuring the wiring circuits and metal configuring the solder conductor 9 having a melting temperature higher than a component mounting temperature is formed in the via hole 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer circuit board in which electrical connection of a wiring circuit is made by a via hole filled with a solder conductor and a method for manufacturing the same, and more particularly,
The present invention relates to a multilayer circuit board having high connection reliability even when components are mounted, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, various interlayer connection methods using via holes are known as electrical interlayer connection methods for multilayer circuit boards. More specifically, a method has been proposed in which a metal powder such as copper powder or silver powder dispersed in a resin is filled in the via hole, or the via hole is filled by copper plating. Against this background, the inventors of the present invention have also proposed a multilayer circuit board in which interlayer connection is made by filling a via hole with a conductor made of solder (a conductor formed of solder powder, tackifying resin, etc.). ing.

However, when a component such as a chip is mounted on the multilayer circuit board in which the via conductor is filled with the solder conductor, a connection failure may occur due to the solder conductor. This is because when the multilayer circuit board itself is exposed to a temperature of 250 ° C. or higher during component mounting and the solder conductor remelts, and the adhesion around the via hole is insufficient, the remelted solder This is because the conductor flows to the interface between the conductor layer and the insulating layer and causes poor connection.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and provides a multilayer circuit board having high connection reliability even when components are mounted, and a manufacturing method thereof. This is an issue.

[0005]

In order to solve such a problem, the present invention provides a multi-layer circuit board having conductor layers for forming a wiring circuit formed on both surfaces of an insulating layer as described in claim 1. Then, the wiring circuits formed on the both sides are
It is electrically connected by a via hole filled with a solder electric conductor in which a metal powder is dispersed, and in the via hole, a metal that constitutes the wiring circuit and a metal that constitutes the solder electric conductor, It is intended to provide a multilayer circuit board characterized in that an alloy having a melting temperature higher than a component mounting temperature is formed.

According to the first aspect of the invention, by dispersing a metal powder (for example, nickel) in the solder-made conductor,
According to the present invention, an alloy of a metal (for example, copper) that constitutes a wiring circuit and a metal (for example, tin) that constitutes a solder-made conductor is formed in the entire via hole with the metal powder as a core. They were found and completed.
For example, Cu ₆ Sn _5, which is an alloy of copper and tin, has a melting temperature of 415 ° C. or higher, and Cu ₃ Sn has a higher melting temperature. On the other hand, since the component mounting temperature is usually around the solder melting temperature, the above-exemplified alloy of copper and tin has a melting temperature higher than the component mounting temperature (solder melting temperature). I can say. The invention according to claim 1 is
Not limited to alloys of copper and tin, as long as the alloy of the metal forming the wiring circuit and the metal forming the solder conductor has a melting temperature higher than the component mounting temperature, various configurations are included. Since the alloy is formed in the entire via hole with the metal powder as a core, it is possible to obtain high connection reliability even when mounting components.

Preferably, the conductor layer forming the wiring circuit is a copper layer.

Further, the metal constituting the conductor made of solder filled in the via hole is melted in the manufacturing process, and the molten metal comes into contact with the wiring circuit, so that the metal constituting the wiring circuit is partially melted. Will be done. In other words,
The wiring circuit is immersed in the molten metal, and a part of the metal forming the wiring circuit is eluted. As described above, the eluted metal forms an alloy with the metal forming the solder-made conductor by using the metal powder dispersed in the via hole as a nucleus. Therefore, as described in claim 3, the wiring circuit is partially eroded by the formation of the alloy.

Preferably, the solder conductor is Sn, Pb, Ag, Cu, Bi and Z.
It is composed of at least one metal selected from n or an alloy of these metals.

Preferably, as described in claim 5, the alloy formed in the via hole is an alloy containing Sn and Cu as main components.

Preferably, the melting point of the metal powder is 350 ° C. or higher.

[0012] Preferably, the metal powder is Ni, Au, Ag, Cu, Fe, Al or C.
At least one metal selected from r, Pd, Co and Rh, or an alloy of these metals is used.

Preferably, as described in claim 8, the solder conductor is formed by filling a paste containing a solder powder and thermocompression bonding.

The present invention also provides a method for manufacturing a multilayer circuit board according to any one of claims 1 to 8, which is a first method.
Forming a thermosetting adhesive layer having an opening on the conductor layer, or forming an opening after forming the thermosetting adhesive layer on the first conductor layer; A step of filling the opening with solder powder and a metal powder at 5 to 50 ° C., and a second conductor layer on the thermosetting adhesive layer including the opening filled with the solder powder and the metal powder And a step of heating and melting the solder powder to electrically connect the first conductor layer and the second conductor layer to each other. Is also provided.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for manufacturing a multilayer circuit board according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an explanatory view showing an embodiment (a method for manufacturing a double-sided circuit board in this embodiment) of a method for manufacturing a multilayer circuit board according to the present invention. Each shows the longitudinal cross-sectional view of the member in each process.

In the method according to the present embodiment, first, as shown in FIG.
As shown in (a), a thermosetting adhesive layer 2 (hereinafter, referred to as “first copper foil 1”, which is a copper foil in the present embodiment) is provided on the first conductor layer 1 (hereinafter, referred to as “first copper foil 1”). Suitable thermosetting adhesive 2
Is formed in a B stage state (a state in which the thermosetting adhesive is being cured to the extent that the thermosetting adhesive can retain a predetermined shape), and then the thermosetting adhesive layer is formed as shown in FIG. 1 (b). The opening 2a is formed in 2.

The thermosetting adhesive 2 is not particularly limited as long as it is usually used for an adhesive layer of a printed circuit board and can be in a B stage state, and for example, an acrylic adhesive or epoxy. A system adhesive, an amide imide adhesive, a polyimide adhesive, and a mixture of these thermosetting adhesives are used. The thermosetting adhesive 2 having a curing temperature of 100 ° C. or higher, preferably 125 to 200 ° C. is preferably used.

As described above, in order to form the thermosetting adhesive layer 2 on the first copper foil 1 in the B stage state, for example, a solution containing the thermosetting adhesive is applied to the first copper foil 1. After being applied on the copper foil 1, it is heated and dried to be in the B stage state at the same time, or an adhesive sheet made of a thermosetting adhesive which has been in the B stage state in advance is applied to the first copper foil 1. above,
Lamination (temporary adhesion) may be performed by heating and / or pressing.

To form the opening 2a in the thermosetting adhesive layer 2, for example, a laser such as a YAG laser may be used to form the opening. When the opening 2a has a circular shape, for example, its diameter is 50 to 300 μm.
m, preferably 50 to 200 μm. It should be noted that instead of forming the opening 2a after forming the thermosetting adhesive layer 2 on the first copper foil 1, the heat in which the opening 2a is previously formed on the first copper foil 1 is formed. The curable adhesive layer 2 may be formed. In this case, for example, an opening 2a is formed in advance on a bonding sheet made of a thermosetting adhesive by using a drill, a punch or the like, and this is used as the thermosetting adhesive layer 2 for the first copper foil. It may be stacked on top of 1.

Further, in the step shown in FIG. 1A, the thermosetting adhesive layer 2 has a metal powder 3 and a metal powder 3 to be described later on the surface opposite to the surface in contact with the first copper foil 1. In order to prevent the solder powder 4 from adhering to unnecessary portions in the step of filling the solder powder 4, the separator 5 is preferably laminated.

As the separator 5, for example, a film of synthetic resin such as polyester resin, polyethylene naphthalate resin or polyimide resin is used, and the thickness thereof is set to 7.5 to 50 μm. The separator 5
Is attached to the surface of the thermosetting adhesive layer 2 before the opening 2a is formed, and the opening 2a is formed in the thermosetting adhesive layer 2.
When forming, the portion corresponding to the opening 2a may be opened at the same time.

Next, as shown in FIG. 1 (c), the opening 2a of the thermosetting adhesive layer 2 is filled with the metal powder 3 and the solder powder 4 mixed in a predetermined amount at 5 to 50.degree.

The solder powder 4 is not particularly limited, but may be, for example, a binary composition of Sn / Ag, Sn / Cu, Sn / Zn, Sn / Ag / Cu, Sn / A.
A multi-component composition of g / Cu / Bi or the like can be used. The average particle diameter of the solder powder 4 is 50 μm or less, preferably 20 μm or less.

The metal powder 3 is made of Ni, Au, Ag, Cu,
At least one metal selected from Fe, Al, Cr, Pd, Co and Rh, or an alloy of these metals is preferably used. The average particle size of the metal powder 3 is 50 μm or less, preferably 20 μm or less.

The mixing ratio of the metal powder 3 to the solder powder 4 is preferably 0.1 to 60% by weight. If it is smaller than this range, the dispersibility of the metal powder 3 cannot be ensured in the opening 2a, and if it is larger than the above range, the metal powders 3 agglomerate with each other and the melt integration of the solder powders 4 is hindered. is there.

In order to fill each powder into the opening 2a of the thermosetting adhesive layer 2, first, the solder powder 4 and the metal powder 3 are mixed with the solvent 6 to prepare the solder paste 7, and the separator 5 is added. The solder paste 7 as a mask at 5 to 50 ° C.
Preferably, printing is performed in an appropriate amount (about an equivalent amount) on the opening 2a at 10 to 30 ° C., more specifically, at room temperature. It should be noted that "at room temperature" means an atmosphere at room temperature in which heating is not performed.

The solvent 6 is not particularly limited, but in the drying step described below, it is preferably 75 to 200 ° C., preferably
It is preferable to select the solvent 6 that can be removed by drying in the range of 75 to 160 ° C. If the solvent 6 that can be dried at a temperature lower than 75 ° C. is selected, the storage stability and continuous printability of the solder paste 7 may decrease, and if the solvent 6 that can be dried at a temperature higher than 200 ° C. is selected, the drying step In the above, curing of the thermosetting adhesive layer 2 progresses, and the adhesive strength of the interface with the second conductor layer 8 (which is a copper foil in the present embodiment, which will be referred to as the second copper foil 8 hereinafter) described later is increased. This is because it may decrease.

More specifically, as the solvent 6, for example,
In order to impart a thickening effect to an aliphatic alcohol, a cellulose resin is preferably used. The amount of the cellulosic resin added is, for example, solder powder 4
On the other hand, it is about 0.005 to 5% by volume. The solder paste 7 can be prepared, for example, by mixing the solder powder 4, the metal powder 3, and the solvent 6 in a volume ratio of about 9: 1: 10.

Next, as shown in FIG. 1D, the solvent 6 is removed by drying. As described above, the solvent 6 is removed by drying by heating in the range of 75 to 200 ° C., preferably 76 to 160 ° C. for a predetermined time. The drying time depends on the filling amount of the solder paste 7 in the opening 2a,
It is appropriately determined according to the size of the first copper foil 1. In general, if the drying time is too short, the solvent 6 may remain in the opening 2a, causing outgas due to heating, which may cause poor conduction. On the contrary, if the drying time is too long, the thermosetting adhesive layer 2 may be hardened and the adhesive force at the interface with the second copper foil 8 described later may be reduced. From the above viewpoints, the drying time is preferably about 1 to 5 minutes, for example. Through such a drying process, FIG.
As shown in (e), the separator 5 is peeled off.

Next, as shown in FIG. 1 (f), a second copper foil 8 is prepared separately, and the second copper foil 8 is filled with the metal powder 3 and the solder powder 4 in the opening 2a. Is laminated on the thermosetting adhesive layer 2 containing.

Such lamination is carried out by placing a heating / pressurizing device such as a vacuum hot press device on both sides of the first copper foil 1 and the second copper foil 8 and applying pressure and / or heating. Just do it. The pressurizing and / or heating conditions may be appropriately determined according to the size of the first copper foil 1 and the second copper foil 8 and the like, but the pressurizing conditions are, for example, 1 to 10 MPa, and preferably The heating condition is, for example, 160 to 225 ° C., preferably 175 to 5 MPa.
It is set to 200 ° C. As a result, the thermosetting adhesive layer 2 in the B-stage state is cured, and the second copper foil 8 is adhesively laminated on the first copper foil 1 via the thermosetting adhesive layer 2.

Next, as shown in FIG. 1 (g), the solder powder 4 is heated and melted, and the first copper foil 1 and the second copper foil 1 facing each other are melted.
A conductor 9 made of solder is formed to electrically connect to the copper foil 8 of. Here, the heating and melting of the solder powder 4 may be set to a temperature equal to or higher than the melting temperature of the solder powder 4 to be used, and with this heating, it is preferable to pressurize at 1 to 10 MPa, preferably 3 to 5 MPa.

The thermosetting adhesive layer 2 described above is used.
The hardening and the heating and melting of the solder powder 4 may be sequentially performed as separate steps as in the present embodiment, but may be performed simultaneously in the same step by selecting appropriate conditions.

Finally, as shown in FIG. 1 (h), the first copper foil 1 and the second copper foil 8 are formed by an ordinary etching method.
By forming a wiring circuit on the
Opening (via hole) 2a filled with solder conductor 9
Thus, the double-sided circuit board 100 electrically connected can be formed.

In the opening 2a of the double-sided circuit board 100 obtained by the manufacturing method according to the present embodiment described above, the metal (copper or the like) forming the wiring circuit and the solder conductor 9 are formed. An alloy made of metal (such as tin) having a melting temperature higher than the component mounting temperature is formed, and since the alloy is formed in the entire opening 2a with the metal powder 3 as a core, it is also possible to mount the component. It is possible to obtain high connection reliability.

In this embodiment, the second copper foil 8 is laminated on the first copper foil 1, but the number of laminated layers is not limited. By preparing two double-sided circuit boards on which is formed and stacking these, a four-layer circuit board can be formed. In addition, a single-sided circuit board and a double-sided circuit board are prepared, and these are laminated to form a three-layer circuit board.

[0038]

[Examples] Hereinafter, by showing Examples and Comparative Examples,
The features of the present invention will be further clarified.

Example 1 In this example, two copper foils 1 are used.
0 and 11 (thickness 18 μm) and an adhesive sheet 12 made of an aromatic amide adhesive were prepared.

As shown in FIG. 2A, an adhesive sheet 12 is further provided on the copper foil 10, and a polyethylene naphthalate film 13 having a thickness of 12 μm is further provided thereon at 150 ° C. using a vacuum press machine. Temporary adhesion was performed under the conditions of 1.5 MPa and 3 min.

Next, as shown in FIG. 2B, the copper foil 10
YAG is attached at a predetermined position of the adhesive sheet 12 laminated on the
The opening 12a (150 μmφ) was formed using a laser.

Next, as shown in FIG. 2C, the opening 1
After the Sn / Ag solder paste 14 (average particle diameter 10 μm) is printed on 2a by screen printing using the polyethylene naphthalate film 13 as a mask, 16
It was dried at 0 ° C. for 5 minutes to remove the solvent component contained in the solder paste 14. Here, as the solder paste 14, Sn / Ag powder as solder powder, Ni powder as metal powder, alcohol solvent and ethyl cellulose are mixed in a volume ratio of 40: 10: 49.5: 0.5. Was used.

Next, as shown in FIG. 2D, after the polyethylene naphthalate film 13 is peeled off, the opening 1
By laminating the copper foil 11 on the base material 15 in which 2a is filled with solder powder and Ni powder, and heating and pressurizing (200 ° C., 3 MPa, 30 minutes) under vacuum (10 mmHg or less), these are Integrated. In this state, the adhesive sheet 12 becomes the insulating layer 16.

Next, as shown in FIG. 2 (e), under vacuum pressure (10 mmHg or less, 3 MPa), the temperature is raised to the melting temperature of the solder powder or higher (250 ° C.), and the melted and integrated solder conductive material is obtained. Body 17 was formed.

Finally, as shown in FIG. 2 (f), the wiring circuits 10a, 1 are formed on the copper foils 10, 11 by an etching method.
1a was formed to obtain a double-sided circuit board 200.

(Embodiment 2) In this embodiment, two double-sided circuit substrates 18, 19 (trade name "ESPANEX", Cu /
PI / Cu = 18/13/18 μm) and an adhesive sheet 20 made of an aromatic amide adhesive were prepared.

As shown in FIG. 3A, the double-sided circuit substrate 1
8, an adhesive sheet 20 is further provided thereon, and a thickness 12
The polyethylene naphthalate film 21 having a thickness of 150 μm was used at 150 ° C. and 1.5 MPa for 3 mi using a vacuum press machine.
Temporary adhesion was performed under the condition of n.

Next, as shown in FIG. 3B, the adhesive sheet 2 laminated on the wiring circuit 18a of the double-sided circuit substrate 18.
Opening 20a using a YAG laser at a predetermined position of 0
(150 μmφ) was formed.

Next, as shown in FIG. 3C, the opening 2
0a is printed with a Sn / Ag solder paste 22 (average particle diameter 10 μm) by screen printing using the polyethylene naphthalate film 21 as a mask.
It was dried at 0 ° C. for 5 minutes to remove the solvent component contained in the solder paste 22. Here, as the solder paste 22, Sn / Ag powder as solder powder, Ni powder as metal powder, alcohol solvent and ethyl cellulose are mixed in a volume ratio of 40: 10: 49.5: 0.5. Using.

Next, as shown in FIG. 3D, after the polyethylene naphthalate film 21 is peeled off, the opening 2 is formed.
Double-sided circuit board 18 in which solder powder and Ni powder are filled in 0a, and double-sided circuit board 19 in which wiring circuit 19a is formed
And are aligned with each other and laminated, and under vacuum (10 m
mHg or less), heating and pressurization (200 ° C., 3 MPa, 30
These were integrated by carrying out (for a minute). In addition,
In this state, the adhesive sheet 20 becomes the adhesive layer 23.

Next, as shown in FIG. 3 (e), under vacuum pressure (10 mmHg or less, 3 MPa), the temperature is raised above the melting temperature of the solder powder (250 ° C.), and the melted and integrated solder conductive material is obtained. Body 24 was formed. As a result, a four-layer circuit board 25 in which two double-sided circuit base materials were laminated and integrated was obtained.

(Comparative Example 1) A solder paste was prepared by mixing Sn / Ag powder as a solder powder, an alcohol solvent and ethyl cellulose in a volume ratio of 50: 49.5: 0.5. A double-sided circuit board was prepared in the same manner as in Example 1.

(Comparative Example 2) A solder paste was prepared by mixing Sn / Ag powder as a solder powder, an alcohol solvent and ethyl cellulose in a volume ratio of 50: 49.5: 0.5. A four-layer circuit board was prepared in the same manner as in Example 2.

(Evaluation) FIG. 4 shows Example 1 (FIG. 4 (a)).
And the via-hole cross-section photograph of the circuit board obtained by Example 2 (FIG.4 (b)) is shown. Moreover, FIG.
(FIG. 5A) and a via hole cross-sectional photograph of the circuit board obtained in Comparative Example 2 (FIG. 5B).

As shown in FIG. 5, the via holes obtained in Comparative Examples 1 and 2 were S
Although the alloy composed of n / Cu was formed, it was observed that the bulk layer was formed of a solder-made conductor mainly composed of Sn.

On the other hand, as shown in FIG. 4, it was observed that in the via holes obtained in Examples 1 and 2, an alloy mainly composed of Sn / Cu was formed even in the bulk layer.

Based on the above results, Sn and Sn /
When the melting temperature of Cu was measured, Sn was 2
While melting at 00 to 225 ° C, melting of the alloy made of Sn / Cu was not observed even at 400 ° C. Therefore, it is apparent that the heat resistance of the entire via hole is improved by forming such an alloy in the entire via hole.

Further, a moisture absorption reflow test was performed using the double-sided circuit boards of Example 1 and Comparative Example 1 and the four-layer circuit boards of Example 2 and Comparative Example 2. The results are shown in Table 1. The test conditions are 16 at 85 ° C. and 60% RH.
After absorbing moisture for 8 hours, the IR reflow test was repeated 3 times. The maximum reflow temperature was 260 ° C.

[Table 1]

As shown in Table 1, in the double-sided circuit board of Example 1 in which the alloy was formed in the via hole and the four-layer circuit board of Example 2, the resistance variation in the via hole before and after the reflow test. I found it small. This is IR
In the reflow test, most of the inside of the via hole (alloy)
Shows that a high connection reliability was obtained because of not remelting.

[0060]

As described above, the multilayer circuit board according to the present invention is composed of the metal forming the wiring circuit and the metal forming the solder-made conductor, and has a melting temperature higher than the component mounting temperature. Since the alloy that it has is formed over the entire via hole, it has an excellent effect that high connection reliability can be obtained even when components are mounted.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a method for manufacturing a multilayer circuit board according to the present invention.

FIG. 2 is an explanatory diagram illustrating a method for manufacturing the multilayer circuit board according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating a method for manufacturing a multilayer circuit board according to a second embodiment.

FIG. 4 shows a photograph of a cross section of a via hole of the circuit board obtained in Example 1 and Example 2.

FIG. 5 shows photographs of cross-sections of via holes of the circuit boards obtained in Comparative Example 1 and Comparative Example 2.

[Explanation of symbols]

1 ... the first copper foil 2 ... Thermosetting adhesive layer 2a ... Aperture 3 ... Metal powder 5 ... Separator 6 ... Solvent 8: Second copper foil 9 ... Solder conductor 100 ... Double-sided circuit board

Continued front page    (72) Inventor Toshikazu Baba             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. F-term (reference) 5E317 AA24 BB12 BB18 CC17 CC25                       CD32                 5E346 AA43 CC08 CC10 CC32 DD12                       FF19 GG15 HH07

Claims (9)

[Claims] 1. A multilayer circuit board in which conductor layers constituting a wiring circuit are formed on both surfaces of an insulating layer, wherein each wiring circuit formed on each of the both surfaces is made of a solder conductor in which a metal powder is dispersed. It is electrically connected by a filled via hole, and the via hole is made of a metal forming the wiring circuit and a metal forming a solder-made conductor, and has a melting temperature higher than a component mounting temperature. A multi-layer circuit board, characterized in that an alloy is formed. 2. The multilayer circuit board according to claim 1, wherein the conductor layer forming the wiring circuit is a copper layer. 3. The wiring circuit is partially eroded by the formation of the alloy.
The multi-layer circuit board according to. 4. The solder conductor is made of Sn, Pb, A.
4. The multilayer circuit board according to claim 1, wherein the multilayer circuit board is made of at least one metal selected from g, Cu, Bi and Zn, or an alloy of these metals. 5. The multilayer circuit board according to claim 1, wherein the alloy formed in the via hole is an alloy containing Sn and Cu as main components. 6. The multilayer circuit board according to claim 1, wherein the metal powder has a melting point of 350 ° C. or higher. 7. The metal powder is Ni, Au, Ag, C.
7. The multilayer circuit board according to claim 1, which is at least one metal selected from u, Fe, Al, Cr, Pd, Co and Rh, or an alloy of these metals. 8. The multilayer circuit board according to claim 1, wherein the solder conductor is formed by filling a paste containing solder powder and metal powder and thermocompression bonding. . 9. A method for manufacturing a multilayer circuit board according to claim 1, wherein a thermosetting adhesive layer having an opening is formed on the first conductor layer. Alternatively, a step of forming an opening after forming a thermosetting adhesive layer on the first conductor layer, a step of filling the opening with solder powder and metal powder at 5 to 50 ° C., Forming a second conductor layer on the thermosetting adhesive layer including the openings filled with solder powder and metal powder; and heating and melting the solder powder to form the first conductor layer. And a step of electrically connecting the second conductor layer to each other.