JPH1154660A - Wiring substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-cost wiring substrate, having a wiring pattern which comprises low-resistance wiring conductor sufficiently resistant to thermal and mechanical stresses and has improved adhesion strength by simultaneously sintering the low-resistance wiring conductor and ceramic insulating base, and covering the peripheral portion of the wiring pattern, comprising fine and high- density low-resistance wiring conductor, with glass component of the insulating base having high precision, without requiring printing process. SOLUTION: In a wiring substrate 1 formed by sintering a molded body containing alkali silicon glass by 20 to 80 vol.% and residue of filler containing metal oxide having a thermal expansion coefficient equal to or higher than 6 ppm/ deg.C at 40 to 400 deg.C, a peripheral portion 4 of a connection pad 3 is covered with a coating layer 6 which contains a glass component of insulating base 2, with a width of 10 to 100 μm from the periphery. Further, the distance between a top portion 7 of the coating layer 6 and the surface of exposed connection pad is set at within 5 μm.

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 device, a hybrid integrated circuit device for mounting various electronic parts such as a capacitor and a resistor in addition to the semiconductor device, and more particularly to a hybrid integrated circuit device. The present invention relates to a wiring board having a fine, high-adhesion strength, low-resistance wiring conductor pattern suitable for directly connecting a surface electrode of a semiconductor element to a wiring electrode of a wiring board or surface mounting a wiring board on an external electric circuit board. It is.

[0002]

2. Description of the Related Art Conventionally, as an insulating base for various wiring substrates such as a package for accommodating a semiconductor element such as an IC or an LSI or a hybrid integrated circuit device having various electronic components mounted thereon in addition to the semiconductor element. Alumina ceramics have been widely used because of their excellent properties such as electrical insulation and chemical stability.

However, in recent years, a wiring board on which a semiconductor element such as an IC or an LSI which has been operated at a higher frequency and a higher density is mounted has a lower dielectric constant and a lower wiring resistance than the insulating base made of alumina ceramics. Glass insulators are required as such insulating substrates, and low-resistance conductors that can be co-fired with the glass ceramics and have low firing temperatures include, for example, copper (Cu), gold (Au), and silver (Ag). ) Is attracting attention.

An insulating substrate made of the above glass ceramic has been developed as a glass ceramic wiring board combined with a low-resistance conductor for a wiring board used in a communication field where the frequency and density are increasing. Wiring using copper as a resistance conductor has been eagerly developed.

[0005] Such a glass ceramic wiring board is formed, for example, by forming a slurry prepared using a glass ceramic raw material powder, an organic binder and a solvent by a sheet forming method such as a doctor blade method, and then forming a via hole in the obtained glass ceramic green sheet. And the like, and a predetermined wiring pattern is printed and formed on the green sheet by using a copper paste containing a copper metallizing composition by a conventionally known thick film method such as a screen printing method. , A plurality of them are laminated under pressure, and then the laminate is heated to remove the binder, and then fired.

However, since the copper paste has a problem in wettability with glass ceramics, the adhesive strength between the formed wiring conductor and the glass ceramic porcelain is low, and high adhesive strength such as a pad portion for a pin or a ball is used. However, there has been a problem that the parts that require the above-mentioned properties are easily peeled off when a thermal or mechanical stress is applied.

Therefore, in order to improve the adhesive strength,
As shown in FIG. 3, the peripheral portion 14 of the wiring pattern 13 provided on the insulating substrate surface 12 is covered with a coating layer 15 made of a paste containing ceramic as a main component or a ceramic green sheet.
There have been proposed various wiring substrates 16 which are covered and fired and integrated (Japanese Patent Laid-Open Nos. 2-130845 and 59-2).
No. 6986).

[0008]

However, although the bonding strength can be improved with the proposed wiring board, the printing position accuracy of the screen printing method, the dimensional accuracy due to expansion and contraction of the ceramic green sheet itself, and the stacking position accuracy thereof are not sufficient. The width 1 of the covering layer at the peripheral portion 14 of the wiring pattern.
7 is required to be 100 μm or more, so that a flip-chip connecting portion requiring fine wiring processing technology,
There is a problem that it is difficult to apply to a wire bonding pattern or the like having a narrow wiring width.

In addition, when coating with the paste, the paste is prepared by mixing the raw material powder with a binder, a solvent and a dispersant, and then printed at a predetermined position on a green sheet by a screen printing method. There is also a problem that the number of steps increases due to the necessity of application, which contributes to an increase in manufacturing cost.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to enable simultaneous firing of a low-resistance wiring conductor and a ceramic insulating substrate, and to separately perform a printing step by a screen printing method or the like. It is possible to cover the peripheral portion of a wiring pattern requiring high adhesive strength, such as a connection pad portion made of a fine and high-density low-resistance wiring conductor, with high precision with the composition component of the ceramic insulating base without the need for It is an object of the present invention to provide a low-cost wiring board having a wiring pattern made of a low-resistance wiring conductor that can improve the adhesive strength of a wiring pattern made of a resistance wiring conductor and sufficiently withstand thermal and mechanical stress.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, have controlled the composition of the ceramic sintered body constituting the insulating substrate and the firing conditions such as the firing temperature, firing time, and firing atmosphere. By doing, among the constituent components of the insulating base, the glass component permeates between the low-resistance wiring conductor particles,
It has been found that the periphery of the wiring pattern can be covered with good reproducibility and high accuracy by oozing onto the surface of the wiring pattern made of the low-resistance wiring conductor.

That is, the wiring board of the present invention contains 20 to 80% by volume of alkali silicate glass and 80 to 20% by volume of a filler containing a metal oxide having a thermal expansion coefficient of 6 ppm / ° C. or more at 40 to 400 ° C. And a wiring pattern made of a low-resistance wiring conductor are simultaneously fired at a temperature of 850 to 1080 ° C. in a non-oxidizing atmosphere to form an insulating base made of a ceramic sintered body. By integrally forming a wiring pattern composed of a low-resistance wiring conductor, the peripheral portions of the input / output connection pad portions forming the wiring pattern adhered to the surface of the insulating base are each 10 to 100 μm from the peripheral edge. The height difference between the top of the coating layer and the exposed surface of the connection pad portion is at most 5 μm, which is covered with a coating layer made of a glass component that has oozed out of the insulating substrate at a width. It is characterized by being.

[0013]

According to the present invention, the composition and the sintering conditions of the ceramic sintered body constituting the insulating base are set in the wiring board obtained by integrally sintering the wiring pattern composed of the low-resistance wiring conductor. The viscosity of the glass component in the ceramic sintered body is reduced to be in a softened and fluidized state, and penetrates between the low-resistance conductor particles constituting the low-resistance wiring conductor, or the softened glass component oozes out on the surface of the wiring pattern. As a result, the peripheral portion of the wiring pattern is covered with a constant width, and it is possible to adjust the coverage of the peripheral portion of the wiring pattern by controlling the composition of the ceramic sintered body and the firing conditions. In addition, the adhesive strength between the wiring pattern made of the low-resistance wiring conductor and the insulating base can be secured.

[0014]

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

FIG. 1 shows a state in which the periphery of an input / output connection pad portion made of a low-resistance wiring conductor provided on a wiring board of the present invention is covered with a coating layer made of a glass component that has oozed from an insulating base. FIG. 2 is a partial sectional view, and FIG. 2 is a plan view of a main part shown in FIG.

In FIGS. 1 and 2, reference numeral 1 denotes a wiring board comprising a connection pad portion 3 provided on the surface of an insulating base 2 and a coating layer 6 covering a peripheral portion 4 of the connection pad portion.

In the wiring board 1, the coating layer 6 made of a glass component constituting the insulating base 2 has a width 5 of 10 to 100 μm from the periphery of the peripheral portion 4 of the connection pad portion.
And the height difference 8 between the top portion 7 of the coating layer and the exposed surface of the connection pad portion is within 5 μm.

In the wiring board according to the present invention, the sintered body constituting the insulating base contains 20 to 80% by volume of alkali silicate glass and a thermal expansion coefficient at 40 to 400 ° C. of 6 ppm /
80 to 20% by volume of a filler containing a metal oxide having a temperature of at least
Of a molded body containing the above-mentioned composition at a ratio of 2.

If the content of the alkali silicate glass component is less than 20% by volume, in other words, if the content of the filler component is more than 80% by volume, liquid phase sintering cannot be performed, and firing at a high temperature must be performed. The low-resistance wiring conductor melts and cannot be fired simultaneously.

If the content of the alkali silicate glass component is more than 80% by volume, in other words, if the filler component is less than 20% by volume, the properties of the sintered body greatly depend on the properties of the alkali silicate glass, and Control becomes difficult and the sintering start temperature becomes too low, so that simultaneous sintering cannot be performed as described above, and also the cost of raw materials increases.

The alkali silicate glass is not particularly limited, but may be a low-resistance wiring conductor, especially C
The lithium-based crystallized glass is desirable in that the thermal expansion difference with u can be reduced, and the bonding strength with the insulating substrate is improved, and Li ₂ O is preferably 5 to 30% by weight, particularly 5 to 30% by weight.
Lithium silicate glass containing 20% by weight is preferable because lithium silicate having a high coefficient of thermal expansion can be precipitated during the firing process.

The Li ₂ O has a content of 5% by weight.
If it is less than 3, the amount of lithium silicic acid crystal generated during firing is small and high thermal expansion cannot be expected. If it exceeds 30% by weight, the dielectric loss tangent tends to exceed 100 × 10 ⁻⁴ .

The yield point of the lithium silicate glass is preferably from 400 to 800 ° C., particularly preferably from 400 to 650 ° C. in consideration of simultaneous sintering with a low-resistance wiring conductor such as Cu and removal of an organic binder. .

Further, the crystalline glass has a coefficient of thermal expansion at 40 to 400 ° C. of 6 to 18 ppm / ° C., especially 7 to 13 p.
When the thermal expansion coefficient is pm / ° C., the sintered body strength can be maintained high without causing a difference in thermal expansion with the filler, and when the thermal expansion coefficient of the filler is less than 6 ppm / ° C., it is difficult to increase the thermal expansion of the sintered body. Becomes

Therefore, as a crystalline glass satisfying this property, for example, SiO ₂ —Li ₂ O—Al ₂ O ₃ SiO ₂ —Li ₂ O—Al ₂ O ₃ —MgO—TiO ₂ SiO ₂ —Li _{2 O-Al 2 O 3 -MgO-} Na 2 O-
F SiO ₂ —Li ₂ O—Al ₂ O ₃ —K ₂ O—Na ₂ O—
ZnO SiO ₂ —Li ₂ O—Al ₂ O ₃ —K ₂ O—P ₂ O ₅ SiO ₂ —Li ₂ O—Al ₂ O ₃ —K ₂ O—P ₂ O ₅ —
A composition such as ZnO—Na ₂ O SiO ₂ —Li ₂ O—MgO SiO ₂ —Li ₂ O—ZnO is mentioned. The SiO ₂ is an essential component for forming lithium silicic acid, and 60% of the total amount of glass. ~
85% by weight, and the total amount of SiO ₂ and Li ₂ O is 65 to 95% by weight in the total amount of glass.
It is desirable in that lithium silicate crystals are precipitated.

The lithium silicate glass contains B ₂
O ₃ is desirably 1% by weight or less.

On the other hand, as filler components containing a metal oxide having a thermal expansion coefficient of 6 ppm / ° C. or more at 40 to 400 ° C. combined with the lithium silicate glass, cristobalite (SiO ₂ ), quartz (SiO ₂ ), tridymite ( SiO ₂ ), forsterite (2MgOS
iO _2), spinel _{(MgO · Al 2 O 3)} , wollastonite (CaO · SiO _2), Monty Sera Knight _{(CaO · MgO · SiO 2)} , nepheline (Na ₂ O
・ Al ₂ O ₃ .SiO ₂ ), lithium silicate (Li
₂ O.SiO ₂ ), diopside (CaO.MgO.2)
SiO ₂ ), melvinite (3CaO.MgO.2Si)
O ₂ ), Akermite (2CaO.MgO.2Si)
O ₂ ), magnesia (MgO), alumina (Al
₂ O _3), Kanegiaito _{(Na 2 O · Al 2 O} 3 · 2
SiO ₂ ), enstatite (MgO.SiO ₂ ), magnesium borate (2MgO.B ₂ O ₃ ), celsian (BaO.Al ₂ O ₃ .2SiO ₂ ), B ₂ O ₃ .2M
gO.2SiO ₂ , garnite (ZnO.Al
₂ O ₃ ) and petalite (LiAlSi ₄ O ₁₀ ).

In particular, even in the above case, the coefficient of thermal expansion is 8 ppm / ° C.
Those containing the above metal oxides are preferable, and the filler has a thermal expansion coefficient of 18 due to its addition.
It may exceed ppm / ° C., in which case it is necessary to appropriately control the coefficient of thermal expansion by mixing other fillers having a small coefficient of thermal expansion.

The mixture of the alkali silicate glass and the filler is added with a known organic binder for molding,
The sheet is shaped into an arbitrary shape by a desired forming means, for example, by a doctor blade method, a rolling method, a die press or the like, and then fired.

Next, as the low-resistance wiring conductor, Au,
In addition to Ag and Cu, good electrical conductive metals such as aluminum (Al) and nickel (Ni) or compounds thereof can be suitably used, and they can be used in combination. Cu is optimal from the viewpoint of simultaneous sintering with the substrate.

The low-resistance wiring conductor is preferably a spherical or near-spherical powder having an average particle size of 1 to 10 μm from the viewpoint of printing accuracy and sharpness of a wiring pattern by a screen printing method. Is more preferably 3 to 6 μm.

Next, when a wiring paste is prepared using the low-resistance wiring conductor, the binder in the organic vehicle added to the low-resistance wiring conductor powder has excellent thermal decomposability in a nitrogen atmosphere. The acrylic binder, specifically, it is desirable to use an acrylic resin having a molecular weight of 500,000 or less, dibutyl phthalate as the solvent of the vehicle,
Dioctyl phthalate, terpineol, butyl carbitol and the like are suitable, and the amount of the binder is preferably 1.0 to 10.0% by weight.

From the viewpoint of adjusting the shrinkage behavior when simultaneously firing the low-resistance wiring conductor and the insulating base and improving the adhesive strength between the two, glass having a high softening point or Al ₂ O ₃ , M
It is also possible to add a metal oxide such as gO or SiO ₂ .

Next, prior to firing, the organic binder is decomposed and removed in a nitrogen atmosphere at a temperature in the range of 100 to 700 ° C. At this time, the compact is shrunk due to the ease of decomposition and removal of the organic binder. The starting temperature is desirably about 700 to 850 ° C., and it is important to control the properties of the glass component in the molded body, particularly the sagging point as described above.

On the other hand, the sintering is required to be carried out in a non-oxidizing atmosphere, particularly in a nitrogen atmosphere in which the components are adjusted for simplicity, since it is necessary to densify the final insulating substrate to a relative density of 90% or more. Is less than 850 ° C.,
When the temperature exceeds 080 ° C., the low-resistance wiring conductor is melted by the co-firing, and a wiring pattern cannot be formed.

The width of the peripheral portion of the connection pad portion is 10
When the thickness is less than μm, the effect of improving the adhesive strength of the connection pad portion is poor. When the thickness exceeds 100 μm, it is not possible to cope with a fine wiring pattern such as flip-chip connection, so the width is limited to 10 to 100 μm.

Next, if the height difference between the top of the coating layer and the exposed surface of the connection pad portion is 5 μm or more, there is a possibility that the warpage and coplanarity of the wiring board may be affected.
Not desirable.

The wiring pattern of the obtained wiring board has N.sub.2 on the surface to prevent oxidation and improve solder wettability.
i plating is 1-2μm in thickness, Au plating is 0.1μ in thickness
It is desirable to apply about m.

The wiring portion other than the connection pad portion formed on the surface of the wiring board may be covered with the coating layer made of the glass component as long as it is not necessary to directly connect to an external electric circuit. No problem.

[0040]

EXAMPLES The wiring board of the present invention was evaluated based on one example shown below.

First, as the glass ceramic main component of the insulating substrate, a mixture of an alkali silicate glass and a filler component in the kind and ratio shown in Table 1 was used.
A slurry was prepared by adding 100,000 acrylic binders, a plasticizer, a dispersant, and a solvent, and the slurry was formed into a green sheet having an average thickness of 200 μm by a doctor blade method, and then a plurality of through holes were punched out. .

On the other hand, the low-resistance wiring conductor has a softening point of 7 with respect to 100 parts by weight of near-spherical copper powder having an average particle size of 5 μm.
2 parts by weight of borosilicate glass at 50 ° C., 4 parts by weight of an acrylic binder having a molecular weight of 300,000, 3 parts by weight of terpineol, 3 parts by weight of dibutyl phthalate, and 3 parts by weight of butyl carbitol are kneaded. A copper paste for printing was prepared.

Next, the obtained copper paste was filled into the through-holes of the green sheet, and the average of 2
A circular pattern having a thickness of 0 μm and a diameter of 0.5 mm, and a pattern of 2 mm long and 2 mm wide on a green sheet other than the through holes.
A square pattern having a thickness of about 15 mm was formed by printing and forming a square pattern having a thickness of about 15 mm using the green sheet as the uppermost layer and stacking a plurality of other green sheets.

Thereafter, in nitrogen gas whose atmosphere has been adjusted, 1
The binder was removed at a temperature of 00 to 700 ° C., and then fired for 1 hour at a firing temperature shown in Table 1 in a nitrogen atmosphere adjusted in the same manner.

In addition, comparative examples include those using borosilicate glass as the main component of the glass ceramic of the insulating substrate and those using cordierite, anorthite and mullite as the filler component.

[0046]

[Table 1]

The types of the alkali silicate glass and the filler in Table 1 are as shown in Table 2.

[0048]

[Table 2]

With respect to the wiring board for evaluation thus obtained, the width of each coating layer covering the periphery of the circular pattern was measured at four positions in a cross shape using a microscope equipped with a micrometer having a magnification of 200 times. Then, the average value was obtained.

The width of the covering layer was measured in the same manner for the circular pattern and the square pattern at the same time, and it was confirmed that the width was almost the same as that of the circular pattern.

On the other hand, the height difference between the top of the coating layer and the exposed circular pattern surface was determined by cutting the wiring board for evaluation and polishing the cross section passing through the circular pattern to 10% by weight after mirror polishing. Was etched with an aqueous solution of ferric chloride, and its structure was confirmed with a metallographic microscope, and then measured with a scanning electron microscope to evaluate the maximum value as a height difference.

Next, using the above-described wiring board for evaluation, the square wiring pattern was coated with Ni plating of 2 μm thickness and Au plating of 0.1 μm thickness sequentially, and the entire wiring pattern was covered. Possibility, a part that has not been adhered at all or not at all was evaluated as not being able to be plated, and a 0.8 mm diameter tin-plated lead was soldered to the wiring pattern portion, and then the lead was perpendicular to the insulating base. Bending and a tensile test were performed by an autograph, and those having a measured value of 2.0 kg / 2 mm square or less were evaluated as insufficient in adhesive strength between the low-resistance wiring conductor and the insulating base.

[0053]

[Table 3]

As is clear from the table, the adhesive strength of Sample Nos. 14, 15, 22, 23, and 24 of the comparative examples was 2 kg / kg.
Sample Nos. 1 and 25, which are less than 2 mm square, which are out of the claims of the present invention, both have a high firing temperature and melting of the wiring pattern is observed. Sintered, the wiring pattern is not covered with glass component at all, and the adhesive strength is 1.0k
g / 2 mm square and extremely low.

On the other hand, according to the present invention, the coating strength is increased to not less than 3.0 kg / 2 mm square by coating with the glass component, and the height difference between the coating layer and the wiring pattern is within 5 μm. I understand.

The present invention is not limited to the above-described embodiment.

[0057]

As described above in detail, the wiring board of the present invention is characterized in that a molded body of an insulating substrate containing an alkali silicate glass and a filler and a wiring pattern formed of a low-resistance wiring conductor are made of a non-oxidizing material. Simultaneous firing in an atmosphere to integrate, covering the periphery of the connection pad portion on the surface of the insulating substrate with a covering layer made of a glass component of the insulating substrate with a width of 10 to 100 μm from the periphery, and Since the height difference between the top and the exposed surface of the connection pad portion is 5 μm at the maximum, a fine and high-density low-resistance wiring conductor can be formed without a separate printing process such as a screen printing method. The peripheral portion of the connection pad portion can be covered with the composition component of the ceramic insulating base with high accuracy, the adhesive strength of the wiring pattern comprising the low-resistance wiring conductor can be improved, and thermal and mechanical It is possible to obtain a low-cost wiring board having a wiring pattern made of a low-resistance wiring conductor that can sufficiently withstand a mechanical stress.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part in which a peripheral portion of an input / output connection pad portion made of a low-resistance wiring conductor provided on a wiring board of the present invention is covered with a coating layer made of a glass component oozing out of an insulating base. is there.

FIG. 2 is a plan view of a main part shown in FIG.

FIG. 3 is a cross-sectional view of a main part of a conventional wiring board in which a peripheral portion of a wiring pattern provided on the surface of an insulating base is covered with a coating layer made of ceramic slurry or ceramic green sheets.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wiring board 2 Insulating base 3 Connection pad part 4 Peripheral part of connection pad part 5 Width 6 Coating layer 7 Top part of coating layer 8 Height difference from connection pad part surface

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaya Kokubu 1-4 Yamashita-cho, Kokubu-shi, Kagoshima Inside the Kyocera Research Institute (72) Inventor Ken-ichi Nagae 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Research Institute

Claims (1)

[Claims] 1. An alkali silicate glass of 20 to 80% by volume.
And the thermal expansion coefficient at 40 to 400 ° C. is 6 ppm / ° C.
A molded body of an insulating substrate containing the filler containing the metal oxide at a ratio of 80 to 20% by volume and a wiring pattern formed of a low-resistance wiring conductor formed on the molded body are formed in a non-oxidizing atmosphere. A wiring board integrated by firing simultaneously at a temperature of 850 to 1080 ° C., wherein a peripheral portion of an input / output connection pad portion made of a low-resistance wiring conductor adhered and formed on the surface of the insulating base is It is covered with a coating layer made of a glass component leached from the insulating base with a width of 10 to 100 μm from the peripheral edge, and a height difference between the top of the coating layer and the exposed surface of the connection pad portion is within 5 μm. Wiring board.