JPH1126942A - Multilayer wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of cracks in an insulating board and separation of a low-resistance wiring conductor, by providing a specified gap on the interface between a low-resistance wiring conductor having a specified thickness and an insulating layer having the low-resistance wiring conductor within the same layer. SOLUTION: On the boundary between an insulating base 3 made of a plurality of insulating layers 2 and the insulating layers 2 on the surface thereof, a low-resistance wiring conductor 6 having a gap 4 of 0.01 to 0.5 mm integrally provided thereon and having a thickness not smaller than 50 μm is provided. The low-resistance wiring conductor 6 formed on the outermost surface is connected to a wiring conductor 8 between the insulating layers from a via-hole conductor 7 connected to the low- resistance wiring conductor 6 provided on the inner insulating layer 2, and is further connected to a via-hole conductor 9. Also, this low-resistance wiring conductor 6 is connected to a via-hole conductor 10 provided on the other outermost surface, and is led out to the other surface of the insulating base 3. Thus, crack of the insulating base and separation of the low-resistance wiring conductor are not generated. Therefore, the thickness of the low-resistance wiring conductor can be increased, and higher density and lower resistance can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for accommodating a semiconductor element in which a semiconductor element is accommodated and mounted, and a hybrid integrated circuit device in which various electronic components such as a capacitor and a resistor are mounted in addition to the semiconductor element. The present invention relates to a multilayer wiring board having a low-resistance wiring conductor through which a large current can flow.

[0002]

2. Description of the Related Art Conventionally, a multilayer wiring board used for a package for housing a semiconductor element, a hybrid integrated circuit device or the like generally uses an insulating substrate made of an electrically insulating ceramic sintered body such as an alumina sintered body. Tungsten (W), molybdenum (Mo), manganese (M)
n) and a plurality of wiring conductors made of a high melting point metal are arranged, and each wiring conductor is connected to a via hole conductor made of the same high melting point metal provided in the insulating base.

When the multilayer wiring board constructed as described above is applied to, for example, a package for accommodating a semiconductor element, the semiconductor element is attached to the bottom surface of the concave portion of the insulating base by an adhesive such as glass, resin, brazing material or the like. Each electrode of the semiconductor element is electrically connected to a wiring conductor located around the concave portion via a bonding wire, and the lid is made of metal, ceramics, or the like, so that the lid is closed so as to cover the concave portion. A semiconductor device as a final product has been obtained by bonding via a sealing agent similar to the agent and hermetically housing the semiconductor element in a concave portion of the insulating base.

In such a semiconductor device, an external lead terminal made of an iron-nickel (Fe-Ni) alloy or the like is attached to a part of a wiring conductor provided on the insulating base via a brazing material such as silver brazing. By connecting the external lead terminal to an external electric circuit, each electrode of the semiconductor element is electrically connected to the external electric circuit via a wiring conductor, a bonding wire and the external lead terminal.

However, in the conventional multilayer wiring board, since the electrical resistance of W or Mo forming the wiring conductor and the via-hole conductor is extremely high at 4 to 8 × 10 ⁻⁶ Ω · cm, the electrical resistance between the wirings is low. , For example, 25-6
It is used in a multilayer wiring board which is required to be able to flow a large current of 0 A, specifically, in a severe environment such as an on-vehicle environment, for example, where it is desired to lower the resistance of a wiring conductor in recent years. It could not be applied to applications such as various control devices.

Accordingly, in order to reduce the resistance value of the wiring conductor in the above-described multilayer wiring board and allow a large current to flow, the insulating base constituting the multilayer wiring board is made of copper (C).
The wiring conductor is formed by a thick film u) or electroless plating.

However, in such a wiring conductor, the line width of the wiring pattern is limited by the area of the multilayer wiring board in order to increase the wiring density, and cannot be formed wider than a certain width. In the formation method, it is difficult to obtain a wiring conductor having a sufficient thickness at a low cost in a short time without adversely affecting the subsequent steps, and the above-mentioned low resistance has not been satisfied.

Therefore, in order to reduce the resistance value of the wiring conductor and allow a large current to flow, a wiring space or groove is formed in an insulating base constituting the multilayer wiring board, and the wiring space or groove is formed. A low-resistance wiring conductor is proposed by thickly filling a wiring conductor material made of a low melting point metal such as copper (Cu) or silver (Ag) having a low electric resistance value (Japanese Patent Laid-Open No. 5-216).
No. 35, JP-A-63-194).

[0009]

However, if the low-resistance wiring conductor is formed to be thicker than, for example, 50 μm, the thermal stress caused by the difference in thermal expansion between the low-resistance wiring conductor and the insulating base is generated in the multilayer wiring board. Residual, in particular, stress concentrates on the ceramics near the end of the low-resistance wiring conductor and becomes a large stress, and as a result, cracks are generated in the insulating base or the cracks develop and break other wiring conductors. Or the low-resistance wiring conductor formed by filling the wiring space or groove of the insulating base is separated from the wiring space or groove and disconnected from other wiring conductors connected to the low-resistance wiring conductor. There were problems such as fear.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a low-resistance wiring conductor having a thickness of 50 μm or more on an insulating substrate. Cracks in the insulating base due to the difference in thermal expansion, breakage of other wiring conductors due to the progress of the cracks, etc. do not occur. A multilayer having a highly reliable low-resistance wiring conductor capable of realizing a low resistance of the wiring conductor and allowing a large current to flow without breaking other wiring conductors connected to the resistance wiring conductor. It is to provide a wiring board.

[0011]

Means for Solving the Problems As a result of extensive studies to achieve the above object, the present inventors have found that a multilayer wiring board in which a low-resistance wiring conductor is integrated with an insulating base made up of a plurality of insulating layers has a large thickness. By providing a gap at the interface between a low-resistance wiring conductor having a thickness of 50 μm or more and an insulating layer having the low-resistance wiring conductor in the same layer, the above-described problems such as cracking of the insulating base and peeling of the low-resistance wiring conductor are solved. The inventors have found that the problem can be solved, and have reached the present invention.

That is, in the multilayer wiring board of the present invention, a low-resistance wiring conductor having a thickness of 50 μm or more integrated with an insulating base composed of a plurality of insulating layers has the low-resistance wiring conductor in the same layer. 0.01 to 0. 0 at the boundary with the low-resistance wiring conductor.
It has a gap of 5 mm.

[0013]

According to the multilayer wiring board of the present invention, a gap is provided at the boundary between the low-resistance wiring conductor of the insulating layer and the low-resistance wiring conductor having a thickness of 50 μm or more integrated with the insulating base in the same layer. Therefore, no thermal stress is generated at all due to the difference in the coefficient of thermal expansion between the insulating base and the low-resistance wiring conductor, so that all the problems involving the thermal stress are eliminated, and cracks and low The resistive wiring conductor does not peel off from the wiring space or groove of the insulating base and break other wiring conductors connected to the low-resistance wiring conductor. Will be able to shed

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multilayer wiring board according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the multilayer wiring board of the present invention, and FIG. 2 is a perspective view of the multilayer wiring board of the present invention cut along a section including a low-resistance wiring conductor.

In FIGS. 1 and 2, reference numeral 1 denotes a unit of 50 μm or more integrated with a gap 4 at a boundary between an insulating base 3 composed of a plurality of insulating layers 2 and the insulating layer 2 on the surface of the insulating base 3. This is a multilayer wiring board provided with a low-resistance wiring conductor 6 having a thickness of 5.

As shown in FIG. 1, the low-resistance wiring conductor 6 formed on the surface layer of the multilayer wiring board 1 is connected to the via-hole conductor 7 connected to the low-resistance wiring conductor 6 provided on the inner insulating layer 2 and is connected to the wiring between the insulating layers. The conductor 8 is further connected to the via-hole conductor 9 from the wiring conductor 8 and connected to the via-hole conductor 10 provided on the other surface layer, so that the conductor 8 is led out to the other surface of the insulating base 3.

FIG. 3 is a cross-sectional view showing another embodiment of the multilayer wiring board of the present invention. The multilayer wiring board 1 is provided with a gap 4 at one boundary between the insulating layer 2 and a low-resistance wiring board. A plurality of conductors 6 are provided, and a via-hole conductor 7 also serving as a thermal via is led out from the low-resistance wiring conductor 6 to the other surface layer and connected to a wiring conductor 11 formed on the surface.

The gap provided at the boundary between the low-resistance wiring conductor and the insulating layer in the multilayer wiring board of the present invention has a length L of the low-resistance wiring conductor perpendicular to the side surface of the low-resistance wiring conductor, difference Δα in thermal expansion coefficient between the thermal expansion coefficient alpha ₂ of the thermal expansion coefficient alpha ₁ and the insulating substrate of the low-resistance wiring conductors, and during operation from the manufacturing process of the insulating substrate between the maximum temperature and the minimum temperature in the total heat history From the correlation with the difference ΔT, L · Δα · ΔT / 2 (1-Δ
T · α ₂ ) is theoretically calculated as the required gap.

However, if the gap is less than 0.01 mm, it may not be possible to completely prevent the generation of the thermal stress. In addition, for example, in order to provide a low-resistance wiring conductor, the wiring space of the insulating base is required. When the conductive groove is formed by heating after filling the conductive material powder into the grooves or grooves, the linear shrinkage of the conductive material can be controlled to about 0.1% by blending the particle size of the conductive material powder. However, since the firing shrinkage varies, it is difficult to control the gap to less than 0.01 mm.

Further, if the gap exceeds 0.5 mm, it is impossible to increase the density of the wiring of the multilayer wiring board. Further, when applying an overcoat layer or solder coating on the wiring by a screen printing method, the overcoating is not possible. Agent or solder cannot enter the gap to form a predetermined print pattern,
The gap is limited to the range of 0.01 to 0.5 mm because the coating amount varies and other problems such as the coating cannot be performed while maintaining the gap by the plating method.

In the present invention, the thickness of the low-resistance wiring conductor is set to 50 μm or more in order to reduce the resistance of the low-resistance wiring conductor and to solve the above-mentioned problem.

In the multilayer wiring board of the present invention, the conductive material constituting the low-resistance wiring conductor may be any conductive material having low resistance and capable of flowing a large current, such as copper (Cu) or silver ( Ag), aluminum (Al), etc., and particularly, copper (Cu) is most suitable in terms of excellent thermal conductivity, easy processing and low cost.

The via-hole conductor may be a conductor mainly composed of a high melting point metal such as tungsten (W), molybdenum (Mo), rhenium (Re), or cobalt (Co). Mo is preferred from the viewpoints of consistency and cost.

On the other hand, as for the wiring conductor, when the insulating base made of ceramics and the wiring conductor are formed by simultaneous firing, the same high melting point metal as the through-hole conductor can be used, and furthermore, heat conductivity and low resistance wiring are required. In the case of copper (Cu) or silver (A) by a post-fire method or a plating method,
g), nickel (Ni), aluminum (Al), and the like. In the case of the simultaneous firing, W is determined from the relationship between the firing temperature and the melting point. , Cu are preferred.

Also, the via-hole conductor has the effect of the low-resistance wiring conductor and the heat sink by connecting the heat generated from the surface-mounted power MOSFET and the like to the low-resistance wiring conductor formed on the surface layer by heat conduction. Things.

The insulating base is a ceramic sintered body mainly composed of alumina (Al ₂ O ₃ ), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ) or the like generally applied to a multilayer wiring board. If applicable, any can be applied,
In particular, those made of an alumina-based sintered body are desirable. For example, an organic binder and an organic solvent, which are well known in raw material powders such as alumina (Al ₂ O ₃ ), silica (SiO ₂ ), magnesia (MgO), and calcia (CaO), The slurry prepared by adding and mixing a plasticizer, a dispersant, and the like is subjected to a predetermined punching process on ceramic green sheets formed by a sheet forming method such as a well-known doctor blade method or a calendar roll method, and a plurality of the green sheets are laminated. , At about 1600 ° C.

Further, when a power MOSFET or the like requiring a large current is surface-mounted on the multilayer wiring board of the present invention, a low-resistance wiring conductor is also formed on the power MOSFET wiring, and the power It is desirable to provide a large number of via-hole conductors that also serve as thermal vias in the portion where the MOSFET is mounted on the surface, and to improve the heat dissipation property in combination with the heat sink function of the low-resistance wiring conductor.

[0029]

Next, the multilayer wiring board of the present invention was evaluated as follows. First, Al ₂ O ₃ , SiO ₂ , MgO,
A slurry was prepared by adding and mixing an acrylic organic binder, a plasticizer, and a solvent to a raw material powder such as CaO, and the slurry was formed into a sheet having a thickness of about 300 μm by a doctor blade method.

Next, a predetermined portion of the ceramic green sheet is punched to form a low-resistance wiring conductor space and a through hole, and then a predetermined wiring pattern is formed using a printing paste containing W as a main component. And a predetermined paste was filled into the through holes.

Thereafter, a plurality of ceramic green sheets each having a space portion for the low-resistance wiring conductor are laminated to a predetermined thickness, a wiring pattern is formed, and a predetermined paste is applied to the through holes. After laminating a plurality of filled ceramic green sheets, about 1600 ° C
To produce an insulating substrate having a low-resistance wiring conductor space having a length of 50 mm, a width of 5 mm, and a depth of 0.1, 0.5, and 1.0 mm, respectively.

The low resistance wiring conductor space portion of the insulating substrate thus obtained is filled with Cu powder mixed with a particle size with various gaps set in the longitudinal direction as a low resistance wiring conductor, and heated and fused. In addition, similarly, copper foils of which dimensions were determined by setting various gaps in the longitudinal direction were bonded to each other to obtain multilayer wiring boards for evaluation.

A comparative example in which the low-resistance wiring conductor was formed in the space for the low-resistance wiring conductor of the insulating base without providing the gap was used as a comparative example.

Using the multilayer wiring board for evaluation thus obtained, the temperatures of -65 ° C and 150 ° C
30 cycles of cooling and heating with one cycle of addition for one minute
The test was performed up to 00 cycles to perform a liquid tank thermal shock reliability test.

After the above test, the appearance of the joint inside the gap of the multilayer wiring board for evaluation and the four corners of the gap where the thermal stress is most concentrated using a digital microscope, and cracks or peeling of the low resistance wiring conductor. Or the presence or absence of defects such as cracks in the insulating layer.

Thereafter, a copper wire having a diameter of 0.8 mm was bonded to the center of the low-resistance wiring conductor of the multilayer wiring board for evaluation by soldering, and a tensile test was performed at a speed of 10 mm / min. The strength was measured.

On the other hand, the continuity evaluation of the wiring conductors of the multilayer wiring board for evaluation was carried out by conducting a 30,000 current cycle test in which a current of 60 A was applied for 1 minute and cut off as one cycle.
Conduct the cycle, measure the resistance value before and after the energization cycle test, measure the resistance change rate between the low-resistance wiring conductor and the wiring conductor connected to the low-resistance wiring conductor and led out to the other surface of the insulating substrate And the rate of change of resistance is 5% or less,
% Was evaluated as good, 11 to 20% as acceptable, and 21% or more as poor.

[0038]

[Table 1]

As is clear from the table, in each of the sample numbers 1, 7, 13, 19, 25, and 31 of the comparative examples, defects such as cracks and peeling of the low-resistance wiring conductor and cracks of the insulating layer were observed. Sample Nos. 6, 12, and 1 which were observed and had poor continuity and were outside the scope of the present invention.
In each of 8, 24, 30, and 36, the solder penetrated into the voids, and defects such as cracks were observed.

On the other hand, in the present invention, none of the above results was observed, and it was confirmed that the bonding strength was as high as 10.0 kgf / mm ² or more, and that it could sufficiently cope with a large current of 60 A.

Although the embodiments of the present invention have been described with reference to a multilayer wiring board in which a low-resistance wiring conductor is formed on the surface of an insulating base, the present invention is not limited to this and does not depart from the gist of the present invention. Various changes are possible within the range, and for example, the present invention can also be applied to a multilayer wiring board in which the low-resistance wiring conductor is embedded in an insulating base.

[0042]

As described above in detail, according to the multilayer wiring board of the present invention, the insulating layer having a low-resistance wiring conductor having a thickness of 50 μm or more integrated with the insulating base in the same layer is provided. Since a gap of 0.01 to 0.5 mm is provided at the boundary with the wiring conductor, cracks may occur in the insulating base and the low-resistance wiring conductor constituting the multilayer wiring board, and the low-resistance wiring conductor may be insulated. It does not peel off from the substrate, so that there is no disconnection etc. in the wiring conductor connected to the low-resistance wiring conductor or other wiring conductors. Resistance can be realized, and it is possible to operate without failure even in a severe environment such as an in-vehicle environment, which has excellent reliability adaptable to a large current.

[Brief description of the drawings]

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

FIG. 2 is a perspective view of a multilayer wiring board of the present invention cut along a cross section including a low-resistance wiring conductor.

FIG. 3 is a sectional view showing another embodiment of the multilayer wiring board of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer wiring board 2 Insulating layer 3 Insulating base 4 Gap 5 Thickness 6 Low resistance wiring conductor

Claims (1)

[Claims] 1. A multilayer wiring board having a low-resistance wiring conductor having a thickness of 50 μm or more integrated with an insulating base composed of a plurality of insulating layers, wherein the low-resistance wiring conductor and the low-resistance wiring conductor are in the same layer. 0.01 to 0.5 m between the insulating layer
A multilayer wiring board having a gap of m.