JPH09237972A - Multilayered wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To have durability in response to superfining of a circuit and requirements of precision as a wiring board such as a package, etc., to which a semiconductor element is mounted. SOLUTION: In a multilayered wiring board 1 in which there are stacked in a multilayer an insulation layer 2 composed of a composite material mixing uniformly an inorganic filler with organic resin; and a conductive circuit 3 composed of a low resistance metal, the coefficient of thermal expansion of an insulation layer 4 of an outermost layer is smaller than that of an internal insulation layer 5. For instance, inorganic filler contents of low thermal expansion in the insulation layer 4 of an outenrmost layer are larger than that in the internal insulation layer 5, preferably the coefficient of thermal expansion of the outermost layer at room temperature to 250 deg.C is controlled to be 10 to 60×10<-6> / deg.C and the internal insulation layer 30 to 100×10<-6> / deg.C. Further, a semiconductor element is mounted onto an upper face of the insulation layer 4 of an outermost layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring board having an insulating layer made of a composite material of an inorganic filler and an organic resin, which is used for a semiconductor package, a hybrid integrated circuit board or the like.

[0002]

2. Description of the Related Art Hitherto, as a wiring board, for example, a wiring board used for a package accommodating a semiconductor element, a multilayer ceramic wiring board capable of relatively high-density wiring has been widely used. This multilayer ceramic wiring board is composed of an insulating substrate such as alumina and a wiring conductor made of a high melting point metal such as W or Mo formed on the surface thereof, and a concave portion is formed in a part of the insulating substrate. The semiconductor element is housed in the recess, and the recess is hermetically sealed by the lid.

However, since the ceramics constituting such a multilayer ceramic wiring board are hard and brittle, they are likely to be chipped or cracked during the manufacturing process or the transporting process, and the hermetic sealing of the semiconductor element is difficult. There is a problem that yield is low because stopping performance may be impaired.

On the other hand, a multilayer ceramic wiring board is manufactured by printing metallized ink on a green sheet before sintering, laminating and sintering the printed sheet, and in the manufacturing process, it is performed at a high temperature. There is a problem that deformation such as warpage or dimensional variation is liable to occur in the obtained substrate due to firing shrinkage due to firing of the substrate. There was a problem that it was not possible to sufficiently respond to the strict requirements of the above.

Therefore, recently, a printed circuit board has been proposed in which a fine circuit is formed by etching on the surface of a board to which a copper foil is adhered, and then the boards are laminated to form a multilayer. In order to increase the strength of such a printed circuit board, a substrate in which a spherical or fibrous inorganic filler is dispersed in an organic resin has been proposed. Application to a multi-chip module (MCM) or the like in which a large number of semiconductor elements are mounted is also being studied.

[0006]

However, according to the insulating substrate made of the composite material of the organic resin and the inorganic filler, the thermal expansion coefficient of the organic resin which is one component of the composite material is about 100 × 10 ^{−. 6} / ℃, the thermal expansion coefficient of the semiconductor element mounted on the insulating substrate is 2.5
It is significantly different from × 10 ^-6 / ° C. Therefore, when the thermal history is repeatedly applied to the substrate on which the semiconductor element is mounted, the stress generated between the semiconductor element and the substrate causes
There is a problem that the mounting state of the semiconductor element is deteriorated and lacks long-term stability.

It is also possible to match the coefficient of thermal expansion of the insulating substrate with the semiconductor element, but in terms of performance as an insulating substrate, characteristics such as electrical insulation, dielectric constant, dielectric loss or strength, and the internal arrangement. It is also necessary to satisfy the characteristics such as matching of thermal expansion with the conductor circuits and through holes, etc., and recently, there are cases where functions such as capacitors and filters are built in. Matching the coefficient of thermal expansion to the semiconductor element while satisfying the characteristics has been a very difficult problem in terms of material design.

[0008]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that an insulating layer made of a composite material of an inorganic filler and an organic resin and a conductor circuit are laminated in multiple layers. In a multi-layered wiring board, it was found that by reducing the thermal expansion of only the outermost layer, the thermal expansion characteristics of the semiconductor element can be matched while satisfying various required characteristics as the insulating layer of the wiring board. The present invention has been achieved.

That is, the multilayer wiring board of the present invention is a multilayer wiring board in which an insulating layer made of a composite material in which an inorganic filler and an organic resin are uniformly mixed and a conductor circuit made of a low resistance metal are laminated in multiple layers. It is characterized in that the coefficient of thermal expansion of the outermost insulating layer is smaller than the coefficient of thermal expansion of the inner insulating layer, specifically, contains a low thermal expansion inorganic filler in the insulating layer. The content of the low thermal expansion inorganic filler in the outermost insulating layer is higher than that in the inner insulating layer. Further, it is desirable that the low thermal expansion inorganic filler is made of an oxide containing Si.

Further, the coefficient of thermal expansion from room temperature to 250 ° C. is 10 to 60 × 10 ⁻⁶ / ° C. in the outermost insulating layer and 30 to 100 × 10 ⁻⁶ / ° C. in the inner insulating layer. A semiconductor element is mounted on the upper surface of the outermost insulating layer.

[0011]

The high-density multi-layer wiring board of the present invention has a substrate surface made of a composite material in which a filler and a resin are uniformly mixed,
By laminating a circuit board on which a circuit made of low resistance metal such as copper or aluminum is formed by a method such as printing, and by laminating an insulating layer having a lower expansion coefficient than the internal insulating layer on the outermost layer Even if an insulating substrate with high thermal expansion is used to achieve matching with the electrical characteristics and internal conductor circuits, etc., the thermal expansion coefficient can be matched with the semiconductor element, so a severe thermal cycle is applied. Even in such a case, the stress generated between the semiconductor element and the wiring substrate does not deteriorate the mounting state of the semiconductor element, and long-term stability can be obtained.

As a result, while satisfying the demands for ultra-miniaturization and precision of the circuit in the multilayer wiring board, the board for small-sized information equipment such as a portable information terminal which is used under severe conditions and the small-sized thin-film board such as a memory card. As a result, the reliability can be increased.

[0013]

FIG. 1 is a schematic view of a multilayer wiring board according to the present invention. The multilayer wiring board 1 of the present invention includes a plurality of insulating layers 2 and a conductive circuit 3, and the conductive circuits 3 are formed between the insulating layers 2 or on the surface of the insulating layer 2.

According to the present invention, the insulating layer is made of a composite material of an inorganic filler and an organic resin, and the inorganic filler is uniformly dispersed in the organic resin at a ratio of 50 to 80% by volume. is there.

Inorganic fillers constituting this composite material include SiO ₂ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ ,
Known materials such as AlN, SiC, BaTiO ₃ , SrTiO ₃ , zeolite, CaTiO ₃ and aluminum borate can be used. Filler has an average particle size of 20 μm
In addition to the substantially spherical powder of 10 μm or less, optimally 7 μm or less, fibrous or woven fabric having an average aspect ratio of 2 or more, particularly 5 or more, can also be used.

On the other hand, as the organic resin in which the inorganic filler is dispersed, PPE (polyphenylene ether), BT
Resin (bismaleimide triazine), epoxy resin,
It is made of a resin such as a polyimide resin, a fluororesin, and a phenol resin, and it is particularly preferable that the raw material is a thermosetting resin that is liquid at room temperature.

According to the present invention, in the above wiring board, the coefficient of thermal expansion of the outermost insulating layer 4 is equal to that of the inner insulating layer 5.
It is a great feature that it is smaller than the coefficient of thermal expansion. The outermost insulating layer is also composed of a composite material of an inorganic filler and an organic resin, but in order to reduce the thermal expansion coefficient, in order to reduce the thermal expansion coefficient, the thermal expansion coefficient of the inorganic filler is relatively higher than that of the inorganic filler in the internal insulating layer. Or include a small inorganic filler,
When the same filler is used for both the inner and outermost layers,
The content of the filler having a small coefficient of thermal expansion may be larger in the outermost insulating layer than in the inner insulating layer.

Examples of such a filler having a relatively small thermal expansion coefficient include molten SiO ₂ , SiC and Si ₃ N ₄ , and among these, SiO ₂ is most effective.
By using such a filler and controlling the content of the filler, the thermal expansion coefficient of the outermost insulating layer can be approximated to the thermal expansion coefficient of the semiconductor element.

Specifically, the coefficient of thermal expansion of the outermost layer at room temperature to 250 ° C. is 10 to 60 × 10 ⁻⁶ / ° C., and particularly 10 to 10.
40 × 10 ⁻⁶ / ° C., the inner insulating layer is 30 to 100 ×
It is preferably 10 ⁻⁶ / ° C.

The insulating layer having a small coefficient of thermal expansion is formed as an outermost layer on both sides of the uppermost surface and the lowermost surface of the wiring board because the wiring board may be deformed due to the difference in thermal expansion only on the uppermost surface. Is desirable. Then, by mounting the semiconductor element 6 on the surface of these outermost insulating layers or separately via a wiring layer made of polyimide or the like having a low thermal expansion, a highly reliable wiring board can be provided.

In the present invention, the conductor circuit is preferably made of copper, aluminum, gold, silver or the like. Further, a high resistance metal such as Ni-Cr may be used depending on the need of the circuit.

Next, to manufacture the above wiring board,
First, as the insulating layer, the inorganic filler powder and the powder or liquid organic resin are sufficiently mixed by a means such as a kneader, and this is molded into a sheet by a doctor blade method or the like, and then the organic resin is semi-cured. For semi-curing, when the organic resin is a thermoplastic resin, the mixture mixed under heating is cooled, and in the case of a thermosetting resin, it is heated to a temperature slightly lower than a temperature sufficient for complete solidification. Good.

Then, a conductor circuit is formed on the surface of the insulating layer. To form a conductive circuit, after attaching a metal foil such as copper to the insulating layer with an adhesive, form a resist for the circuit pattern and etch away the unnecessary metal with acid or the like, or use a metal foil that has been punched in advance. Stick it. As another method, the conductive paste can be formed on the surface of the insulating layer by screen printing, a photoresist method or the like on the surface of the insulating layer, and then dried and pressed to be adhered to the insulating layer.

Next, if desired, the insulating layer on which the conductor circuit is formed is punched out by forming a via hole by laser processing and filling the conductor, and then laminating a plurality of insulating layers.
The organic resin of the insulating layer is completely cured.

In the present invention, in the above laminating step, an insulating layer having a thermal expansion coefficient smaller than that of the internal insulating layer is laminated on the outermost layer of the multilayer substrate. As described above, the insulating layer having a small coefficient of thermal expansion contains an inorganic filler having a relatively small coefficient of thermal expansion as compared with the inorganic filler in the inner insulating layer, or the same filler is used for both the inner and outermost layers. In such a case, an insulating layer having a larger amount of the filler having a smaller coefficient of thermal expansion in the outermost insulating layer than in the inner insulating layer may be prepared and laminated.

[0026]

Example As an inorganic filler, SiO ₂ powder having an average particle size of 5 μm, SiO ₂ glass fiber having an average aspect ratio of 20, and a short diameter of 10 μm, BaT having an average particle size of 3 μm.
TiO ₃ powder is used, and BT resin (bismaleimide triazine), epoxy resin, phenol resin, PPE (polyphenylene ether), liquid crystal polymer (liquid crystalline aromatic polyester), and polyimide resin are used as an organic resin to insulate them internally. Table 1 for layers and outermost insulating layers
To prepare a slurry. Then, a copper wiring pattern having a thickness of 12 μm formed on the surface of a transfer sheet made of polyethylene terephthalate (PET) resin is preliminarily etched to form a copper wiring pattern, and the slurry is poured into the pattern and heated to be semi-cured. After letting
The transfer sheet was peeled off to form an insulating layer having a circuit pattern.

In the case of using glass cloth as the inorganic filler, a solvent was mixed with the organic resin and the mixed solution was impregnated into the glass cloth. Then, a glass-containing cloth impregnated with an organic resin was placed on the copper wiring pattern and semi-cured by heating, and then the transfer sheet was peeled off to transfer the pattern.

After laminating the five inner insulating layers thus produced and further laminating the outermost insulating layers on the uppermost layer and the lowermost layer, this is heated again and completely cured to produce a multilayer wiring board. did.

The outermost layer and the inner layer are at room temperature to 250
The coefficient of thermal expansion at ° C was measured and is shown in Table 1. Also,
For the obtained substrate, after bonding the semiconductor element to the surface of the outermost layer with a die bonding paste, -40 ° C
Repeated temperature cycle from 100 to 125 ° C
The state of the substrate after the cycle treatment was observed, and the number of defective products in which the mounting state of the semiconductor element was deteriorated and the wiring resistance was changed was shown in Table 1.

[0030]

[Table 1]

Sample No. 1, Sample No. 2 and Sample No. 2 in Table 1
3 and sample No. 4, sample No. 5 and sample No. 6, sample No. 7
As is clear from the comparison between Sample No. 11, Sample No. 11 and Sample No. 12, and Sample No. 13 and Sample No. 14, the product of the present invention in which an insulating layer having a low thermal expansion coefficient is laminated on the outermost layer is made of the same material. With respect to each of the formed samples No. 1, 3, 5, 7, 11, and 13, the defective rate after the thermal cycle test was lowered, and a highly reliable wiring board could be manufactured. Further, as shown in Sample Nos. 15 to 20, it is possible to combine all materials, whereby a highly reliable substrate can be manufactured.

[0032]

As described above in detail, the high-density multilayer wiring board of the present invention has a high thermal expansion insulating layer by laminating an insulating layer having a lower expansion coefficient than the internal insulating layer on the outermost layer of the wiring board. Even when using, because it is possible to match the coefficient of thermal expansion with the semiconductor element, as a wiring board such as a package on which the semiconductor element is mounted, while responding to the demand for ultra-fine and precise circuits, Since it has durability, it can exhibit optimum characteristics as a substrate of a small information device such as a portable information terminal used under severe conditions and a small substrate of a memory card.

[Brief description of drawings]

FIG. 1 is a schematic view of a multilayer wiring board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer wiring board 2 Insulating layer 3 Conductor circuit 4 Outermost insulating layer 5 Inner insulating layer 6 Semiconductor element

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Riichi Sasamori 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Inside the Kyocera Research Institute

Claims (5)

[Claims] 1. A multilayer wiring board in which an insulating layer made of a composite material of an inorganic filler and an organic resin and a conductor circuit made of a low resistance metal are laminated in multiple layers, and the thermal expansion coefficient of the outermost insulating layer. Is smaller than the coefficient of thermal expansion of the internal insulating layer. 2. The low thermal expansion inorganic filler is contained in the insulating layer, and the content of the low thermal expansion inorganic filler in the outermost insulating layer is higher than that in the internal insulating layer. The multilayer wiring board according to claim 1. 3. The multilayer wiring board according to claim 2, wherein the inorganic filler having a low thermal expansion is made of an oxide containing Si. 4. The coefficient of thermal expansion at room temperature to 250 ° C. is 10 to 60 × 10 ⁻⁶ / ° C. for the outermost insulating layer and 30 to 100 × 10 ⁻⁶ / ° C. for the inner insulating layer. The multilayer wiring board according to any one of claims 1 to 3. 5. The multilayer wiring board according to any one of claims 1 to 4, wherein a semiconductor element is mounted on an upper surface of the outermost insulating layer.