JP2000349200A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board which is burned at a temperature of 800 to 1000 deg.C, low in dielectric constant and low in dielectric loss in a high-frequency region, high in mechanical strength, similar to a printed board in thermal expansion coefficient, and high in mounting reliability. SOLUTION: A mixture of 50 to 95 wt.% glass powder which is capable of separating out diopside oxide crystal phase (DI) which contains SiO2, Al2O3, MgO and CaO, and 5 to 50 wt.% in a total weight of quartz powder and/or amorphous silica powder is molded and burned into a porcelain board which contains diopside oxide crystal phase (DI) and SiO2 crystal phase (Si), has a thermal expansion coefficient of 8.5 ppm/ deg.C or above in a temperature range from a room temperature to 400 deg.C, and is made to serve as the insulating board for a wiring board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board applied to a package for accommodating a semiconductor element, a multi-layer wiring board, and the like. The present invention relates to a wiring board which can be mounted on an external circuit board made of an organic resin with high reliability.

[0002]

2. Description of the Related Art Heretofore, as a ceramic multilayer wiring board, a wiring board made of a refractory metal such as tungsten or molybdenum formed on the surface or inside of an insulating substrate made of an alumina sintered body has been most widely used. I have.

Further, recently, with the era of advanced information, the frequency band to be used is shifting to higher and higher frequencies. In such a high-frequency wiring board that requires transmission of a high-frequency signal, in order to transmit a high-frequency signal without loss, the resistance of the conductor forming the wiring layer is small, and the dielectric of the insulating substrate in the high-frequency region is low. Low loss is required.

However, conventional tungsten (W),
Refractory metals such as molybdenum (Mo) have high conductor resistance
Signal propagation speed is slow, and high frequency
Since it is difficult to propagate signals in the wave region, W, Mo, etc.
Use low-resistance metals such as copper, silver, and gold instead of metals
It is necessary. Because of such low resistance metal
The wiring layer has a low melting point and should be co-fired with alumina.
Is impossible, because recently, glass, or glass
So-called glass made of composite material of ceramic and ceramic
Wiring board using ceramics as insulating substrate was developed.
It is getting. For example, JP-A-60-240135
In the case of zinc borosilicate glass, _TwoO_Three, Zirconi
A, low-resistance gold with fillers such as mullite
Multilayer wiring board co-fired with metal
As in No. 19, mullite and cordierite are used as crystalline phases.
Glass ceramic materials deposited by
You.

Further, when mounting a wiring board such as a multilayer wiring board or a package for housing a semiconductor element on a printed board containing an organic resin such as a mother board, a difference in thermal expansion between an insulating board and a chip component or a printed board is caused. It is desired that the thermal expansion coefficient of the insulating substrate is similar to that of the chip component or the printed circuit board from the viewpoint of preventing the mounting portion from peeling or cracking due to the generated stress.

Therefore, the present applicant has previously disclosed in Japanese Patent Laid-Open No. 9-17 / 1997.
As disclosed in Japanese Patent No. 904, it has been proposed that the use of crystallizable lithium silicate glass can increase the thermal expansion coefficient of an insulating substrate.

[0007]

However, the conventional glass ceramic has a thermal expansion coefficient of 3 to 5 even if it can be co-fired with a low-resistance metal such as copper, silver or gold.
ppm / ° C, the printed circuit board (coefficient of thermal expansion 12
-15 ppm / ° C.), the reliability of the mounting was low and was not satisfactory in practice.

In the method using a glass containing an alkali metal as disclosed in Japanese Patent Application Laid-Open No. Hei 9-17904, when exposed to a high-temperature and high-humidity atmosphere for a long time, the alkali metal reacts with the moisture in the atmosphere to produce a surface. In some cases, a silicate crystal phase is precipitated and the surface is deteriorated.

Conventional glass ceramics have not been specifically studied as insulating substrates for wiring boards using high-frequency signals such as millimeter waves, and most of them have high dielectric loss and have satisfactory high-frequency characteristics. Was not.

Therefore, the present invention can be fired at 800 to 1000 ° C., which can be multilayered using gold, silver and copper as wiring conductors, and has a thermal expansion coefficient close to that of a printed circuit board. It is another object of the present invention to provide a wiring board using a porcelain having a low dielectric constant and a low dielectric loss even in a high frequency region as an insulating substrate.

[0011]

Means for Solving the Problems As a result of diligent studies on the above-mentioned problems, the present inventors have found that glass powder containing SiO ₂ , Al ₂ O ₃ , MgO and CaO and capable of precipitating a diopside oxide crystal phase. On the other hand, a composition in which quartz powder and / or amorphous silica powder were blended at a specific ratio was used, and after molding, the composition was fired at a temperature of 800 to 1000 ° C. to form a diopside oxide crystal phase mainly. By precipitating as a crystal phase, it has a low dielectric constant and a thermal expansion coefficient close to the thermal expansion coefficient of a printed circuit board.
Finding that a porcelain suitable for an insulating substrate of a wiring board having low dielectric loss can be obtained even in a high frequency region of z or more,
The present invention has been reached.

That is, the wiring board of the present invention is made of SiO ₂ , A
l ₂ O _3, the glass powder can be precipitated diopside-type oxide crystal phase containing MgO and CaO 50 to 95 wt%
And a mixture containing quartz powder and / or amorphous silica powder in a total amount of 5 to 50% by weight, followed by firing to deposit a diopside oxide crystal phase as a main crystal phase. Is an insulating substrate, and is provided with a ball-shaped terminal attached to the bottom surface of the insulating substrate.

Here, the glass powder is SiO ₂ 45
And 55 wt%, and Al ₂ O ₃ 3 to 10 wt%, MgO1
Desirably, it is composed of 3 to 24% by weight and 20 to 30% by weight of CaO.

The insulating substrate may further comprise SiO ₂
It contains a crystalline phase, has a thermal expansion coefficient of 8.5 ppm / ° C. or more from room temperature to 400 ° C., a dielectric constant of 7 or less, and 60 to 60 ° C.
It is desirable to use a porcelain having a dielectric loss of 15 × 10 ⁻⁴ or less at 77 GHz.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The porcelain composition used as an insulating substrate in the wiring board of the present invention is SiO ₂ , Al ₂ O ₃ , M
A glass powder containing gO and CaO and capable of precipitating a diopside-type oxide crystal phase in a proportion of 50 to 95% by weight and a total of 5 to 50% by weight of quartz powder and / or amorphous silica powder. Things.

The reason for limiting each component composition to the above range is as follows.
If the glass powder is less than 50% by weight, 1000
It is difficult to densify the porcelain by firing at a temperature of not more than 95 ° C., and if it is more than 95% by weight, crystallization of the glass becomes insufficient and a glass phase having a large dielectric loss remains,
This is because dielectric loss at high frequencies of the porcelain increases. A particularly desirable range for the glass powder is 60-85% by weight.

Here, the glass powder desirably has a glass softening point of 500 to 800 ° C., and its composition is 45 to 55% by weight of SiO ₂ , _{3 to} 10% by weight of Al ₂ O ₃ , and 13 to 24% of MgO. Wt%, CaO 20-30 wt%
Is desirable.

Generally, the glass phase containing Al ₂ O ₃ or SiO ₂ has a low thermal expansion coefficient of 4 to 5 ppm / ° C. On the other hand, since the diopside oxide crystal phase of MgCaSi ₂ O ₆ has a high thermal expansion characteristic of about 8 to 9 ppm / ° C., the diopside oxide crystal phase is precipitated from the glass powder having the above composition. Together with 13-20 ppm
By adding a specific amount of quartz having a high thermal expansion coefficient of / ° C, the thermal expansion coefficient can be increased to 8.5 ppm / ° C or more.

Moreover, since diopside and quartz have small dielectric loss in the millimeter wave band, the dielectric loss of the porcelain can be reduced.

The diopside-type oxide crystal phase of MgCaSi ₂ O ₆ has a dielectric constant of 6 to 8, which is added to quartz powder having a dielectric constant of 4 to 4.5 and / or a dielectric constant of 3 to 3. The dielectric constant can be reduced to 5.9 or less by adding a specific amount of amorphous silica powder of 0.8 to 4.2.

In order to increase the precipitation ratio of the diopside oxide crystal phase from the above glass, it is desirable that the total amount of CaO and MgO in the glass is 35 to 50% by weight.

When the total amount of the quartz powder and / or the amorphous silica powder is less than 5% by weight, the residual ratio of the glass increases, and the dielectric loss increases. Conversely, 50
If the content exceeds 10% by weight, sintering becomes difficult, and densification cannot be performed at a firing temperature of 1000 ° C. or less. A desirable range of the total amount of quartz and / or amorphous silica is:
15 to 40% by weight.

The added quartz may undergo a phase transformation to cristobalite, tridymite, etc. in addition to quartz by calcination. Desirably, it remains as quartz in terms of dielectric properties.

[0024] The porcelain composition of the above embodiment has a composition of 800 to 10
By sintering in a temperature range of 00 ° C., the density can be reduced to a relative density of 97% or more, and the overall composition of the porcelain formed thereby is calculated based on oxides of metal elements of Si, Al, Mg and Ca. when the total amount is 100 wt%, a SiO ₂ 55 to 75 wt%, the Al ₂ O ₃ 3 to 5
%, MgO 10-14% by weight, CaO 15-21
Desirably, it consists of a percentage by weight.

As shown in the schematic diagram of the porcelain structure in FIG. 1, the porcelain has a diopside oxide crystal phase MgCaSi ₂ containing at least MgO, CaO and SiO ₂ precipitated from glass as a crystal phase. In addition to O ₆ (DI),
It contains a SiO ₂ crystal phase (Si), and also contains Ca ₂ MgSi ₂ O ₇ (akermanit).
e), CaMgSiO ₄ (monticellit)
e), similar phases with high thermal expansion, such as Ca ₃ MgSi ₂ O ₈ (merwinite), may precipitate.

The porcelain for an insulating substrate in the wiring board of the present invention contains a diopside-type oxide crystal phase containing at least Mg, Ca and Si, and a SiO ₂ crystal phase, and has a heat resistance from room temperature to 400 ° C. Expansion coefficient is 8.5 ppm /
° C or higher, particularly 9 ppm / ° C or higher, dielectric constant of 7 or lower, particularly 6.5 or lower, and a dielectric loss of 15 × 1 at 60 to 77 GHz.
It is important that it is ^0-4 or less.

Therefore, the porcelain composition in the wiring board of the present invention is a porcelain suitable for forming an insulating layer of a high-frequency wiring board of 1 GHz or more, especially 20 GHz or more, further 50 GHz or more, or even 70 GHz or more. is there. According to the present invention, this porcelain is used as an insulating substrate of a wiring board. However, in order to reduce the influence on the transmission characteristics of high-frequency signals, it is desirable that the dielectric constant be as low as 7 or less, particularly 6 or less.

It is desirable that the coefficient of thermal expansion of the porcelain from room temperature to 400 ° C. is appropriately adjusted so as to approximate the coefficient of thermal expansion of the printed circuit board to be mounted. This is because if the thermal expansion coefficient of the porcelain is different from that of the printed board on which it is mounted, the difference in thermal expansion between the printed board and the package due to repeated temperature cycles during solder mounting or when the operation of the semiconductor element is stopped. This causes a stress due to the above, and cracks or the like are generated in the mounting portion, which impairs the reliability of the mounting structure.

Specifically, in order to achieve matching with the printed board, the difference in thermal expansion coefficient between the printed board and the printed board is 2 ppm / ° C.
It is desirable that:

Next, a method of manufacturing a porcelain serving as an insulating substrate using the above-described porcelain composition will be described. First, as a starting material, 50 to 95% by weight of a crystallized glass powder containing SiO ₂ , Al ₂ O ₃ , MgO, and CaO and capable of precipitating a diopside crystal phase, and a total amount of quartz and / or amorphous silica of 5% Weigh and mix at a rate of ５０50% by weight.

Then, using the mixed powder, a molded article having a predetermined shape is produced by a doctor blade method, a calender roll method, a rolling method, or a well-known molding method such as a press molding method. By baking in an oxidizing atmosphere or an inert atmosphere.

In order to manufacture a wiring board having a wiring layer, a slurry is prepared by mixing the mixed powder with an appropriate organic solvent and a solvent, and the slurry is prepared by a conventional doctor blade method or calender roll. It is formed into a sheet by a rolling method or a press forming method. Then, after a through-hole is formed in this sheet-like molded body as desired, the through-hole is filled with a metal paste containing at least one of copper, gold, and silver. Then, on the surface of the sheet-like molded body, the thickness of the wiring layer is reduced to 5 to 3 by a screen printing method, a gravure printing method, or the like using the metal paste in a high-frequency line pattern or the like capable of transmitting a high-frequency signal.
Print and apply so that the thickness becomes 0 μm.

Thereafter, a plurality of sheet-like molded bodies are aligned and laminated and pressed, and fired in a non-oxidizing atmosphere such as a nitrogen gas or a nitrogen-oxygen mixed gas at 800 to 1000 ° C. to produce a wiring substrate. be able to. A chip component such as a semiconductor element is appropriately mounted on the surface of the wiring board, and is connected to the wiring layer so that signals can be transmitted. As a connection method, the chip component is directly mounted on the wiring layer and connected, or a chip component is insulated by a resin of about 50 μm, a resin such as Ag-epoxy, Ag-glass, Au-Si, or an adhesive such as metal or ceramic. The wiring layer is fixed to the substrate surface, and the wiring layer and the semiconductor element are connected by wire bonding, TAB tape, or the like.

As the semiconductor element, a chip component such as a Si-based or GaAs-based component can be used, but it is most effective for mounting a GaAs-based chip component in terms of the similarity of the thermal expansion coefficient.

Further, a cap made of an insulating material of the same kind as the insulating substrate, another insulating material, or a metal having a good heat radiation property and having an electromagnetic wave shielding property is provided on the surface of the wiring board on which the semiconductor element is mounted, with a glass, The semiconductor element may be hermetically sealed by bonding with an adhesive such as a resin or a brazing material.

FIG. 2 shows a specific structure of the wiring board of the present invention in which the above-mentioned ceramic composition can be suitably used and a mounting structure thereof.
It is explained based on. FIG. 2 shows a semiconductor storage package,
In particular, it is a schematic cross-sectional view of a ball grid array (BGA) type package in which connection terminals include ball terminals.

According to FIG. 2, the package A has a cavity 3 formed by an insulating substrate 1 made of an insulating material and a lid 2, in which a chip component 4 such as GaAs is bonded. Implemented by agent.

Further, on the surface and inside of the insulating substrate 1,
A wiring layer 5 electrically connected to the chip component 4 is formed. The wiring layer 5 is desirably made of a low-resistance metal such as copper, silver, or gold in order to minimize conductor loss when transmitting a high-frequency signal. When transmitting a high-frequency signal of 1 GHz or more to the wiring layer 5, it is necessary to transmit the high-frequency signal without loss. Therefore, the wiring layer 5 includes a known strip line, microstrip line, coplanar line, It is composed of at least one of dielectric waveguide lines.

In the package A of FIG. 2, a connection electrode layer 6 is formed on the bottom surface of the insulating substrate 1 and is connected to the wiring layer 5 in the package A. A ball-shaped terminal 8 is formed on the connection electrode layer 6 with a brazing material 7 such as solder.

The package A is connected to an external circuit board B.
As shown in FIG. 2, a polyimide resin,
An external circuit board B having a wiring conductor 10 formed on the surface of an insulating substrate 9 made of an insulating material containing an organic resin such as an epoxy resin or a phenol resin is mounted via a brazing material. Specifically, the ball-shaped terminals 8 attached to the bottom surface of the insulating substrate 1 in the package A and the wiring conductors 10 of the external circuit board B are brought into contact with each other, and the brazing material 11 such as a solder such as Pb-Sn is used. It is mounted with brazing. Further, the ball-shaped terminal 8 itself may be melted and connected to the wiring conductor 10.

According to the present invention, the chip component 4 such as GaAs is mounted on an external circuit board such as a printed board by brazing or mounting with an adhesive or by brazing with such ball-shaped terminals 8 interposed therebetween. In such a surface mount type package, the thermal expansion difference between the external circuit board and the insulating substrate can be made smaller than that of the conventional ceramic material. As a result, the long-term reliability of the mounting structure can be improved.

[0042]

EXAMPLE A crystallized glass capable of precipitating two kinds of diopside oxide crystal phases having the following compositions was prepared. Glass A: SiO ₂ 50 wt% -Al ₂ O ₃ 5.5 wt% -MgO18.5 wt% -CaO26 wt% Glass B: SiO ₂ 52 wt% -Al ₂ O ₃ 5 wt% -MgO18 wt% -CaO25 % By weight and the average particle size is 5
Using a quartz having a particle size of μm and an amorphous silica powder having an average particle size of 2 μm, they were mixed so that the porcelain after firing had the compositions shown in Tables 1 and 2. Then, an organic binder, a plasticizer, and toluene were added to this mixture to prepare a slurry, and then a green sheet having a thickness of 300 μm was produced using the slurry by a doctor blade method. Then, 10 to 15 green sheets were laminated and thermocompression-bonded at a temperature of 50 ° C. by applying a pressure of 100 kg / cm ² . The obtained laminate was subjected to a binder removal treatment in a steam-containing / nitrogen atmosphere at 700 ° C., and then fired in dry nitrogen under the conditions shown in Tables 1 and 2 to obtain a porcelain for an insulating substrate.

The obtained ceramics were evaluated for permittivity and dielectric loss tangent by the following methods. The measurement is shape, diameter 2-7mm,
Cut out to 1.5-2.5mm thickness, 60GHz
, And a dielectric cylinder resonator method using a network analyzer and a synthesized sweeper. In the measurement, the dielectric resonator was excited by an NRD guide (non-radiative dielectric line), and the dielectric constant and the dielectric loss were calculated from the resonance characteristics of the TE ₀₂₁ and TE ₀₃₁ modes.

A thermal expansion curve from room temperature to 400 ° C. was taken to calculate a thermal expansion coefficient. Further, the crystal phase in the sintered body was identified from the X-ray diffraction chart. The results are shown in Tables 1 and 2.

For some of the samples, ZrO ₂ powder and CaZrO ₃ powder were used in place of quartz and amorphous silica as filler components, and porcelain was similarly prepared and evaluated (samples Nos. 7 to 9, 20 to 20). ~ 22). In addition, the same evaluation was performed using glass C having the following composition instead of the crystallized glasses A and B (Sample No. 2).
3, 24). Glass C: SiO ₂ 10.4 wt% -Al ₂ O ₃ 2.5 wt% -B ₂ O ₃ 45.3 wt% -CaO35.2 wt% -Na ₂ O6.6 wt%

[0046]

[Table 1]

[0047]

[Table 2]

As is clear from the results in Tables 1 and 2, Si
The glass content including O ₂ , Al ₂ O ₃ , MgO and CaO is 95
% Of the sample no. At 1, the dielectric loss is 15 × 1
Sample No. ^0-4 was exceeded and the glass content was less than 50% by weight. In Nos. 10 to 12 and 19, it was difficult to perform sintering at a low temperature, and they were not densified. Sample No. 7
-9 and 20-22 are added components to the glass,
Although ZrO ₂ and CaZrO ₃ were blended, ZrO ₂ and CaZrO ₃ were precipitated in the sintered body and dielectric loss increased. In addition, glass C containing a large amount of B ₂ O ₃ is used as the glass.
Using the sample No. In Nos. 23 and 24, a large amount of glass containing B remained and the dielectric loss tended to increase.

On the other hand, according to the present invention, sample no. 2-6, 13, 15
In No. 18, a quartz phase was precipitated in the porcelain,
All have a thermal expansion coefficient of 8.5 ppm / ° C. or more and 60 GH
At the measurement frequency of z, the dielectric constant is 7 or less and the dielectric loss is 15 ×
It had excellent properties of 10 ^-4 or less.

Sample No. 1 containing a specific amount of amorphous silica powder was added. In No. 13, an amorphous silica phase exists in the porcelain, and at a measurement frequency of 60 GHz,
It had excellent characteristics with a dielectric constant of 5.9 or less and a dielectric loss of 15 × 10 ⁻⁴ or less.

[0051]

As described in detail above, according to the wiring board of the present invention, since the insulating substrate can be fired at a low temperature of 1000 ° C. or less, a wiring layer of a low-resistance metal such as copper can be formed, and moreover, 1 GHz or more. In this high-frequency region, a low dielectric constant and a low dielectric loss allow a high-frequency signal to be transmitted very favorably and without loss. In addition, since this insulating substrate can be controlled to have a thermal expansion characteristic similar to that of a printed circuit board, it has excellent heat cycle resistance when mounted on a motherboard such as a printed circuit board having an insulating substrate containing an organic resin with a brazing material or the like. And a highly reliable mounting structure can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining the structure of porcelain obtained by firing a composition of the present invention.

FIG. 2 is a schematic cross-sectional view for explaining an example of a mounting structure of a package for housing a semiconductor element which is an example of a wiring board of the present invention.

[Explanation of symbols]

Si SiO ₂ crystal phase DI Diopside-type oxide crystal phase G Amorphous (glass) phase AM Amorphous silica phase A Package for storing semiconductor elements B External circuit board 1 Insulating substrate 2 Lid 3 Cavity 4 Chip component 5 Wiring layer 6 connecting electrode layer 7 brazing material 8 ball-shaped terminal 9 insulating substrate 10 wiring conductor 11 brazing material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Kumadahara 1-4 Yamashita-cho, Kokubu-shi, Kagoshima Inside the Kyocera Research Institute (72) Inventor Yasuhide Minami 1-4-Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Research Institute

Claims (3)

[Claims] 2. The method according to claim 1, wherein the first and _second layers are SiO ₂ , Al ₂ O ₃ , MgO and CaO.
After forming a mixture containing 50 to 95% by weight of a glass powder capable of precipitating a diopside type oxide crystal phase containing and 5 to 50% by weight of a quartz powder and / or an amorphous silica powder, firing is performed. A wiring board, comprising: a porcelain formed by depositing a diopside oxide crystal phase as a main crystal phase, as an insulating substrate, and ball-shaped terminals attached to the bottom surface of the insulating substrate. 2. The glass powder comprises 45 to 55% by weight of SiO ₂ , _{3 to} 10% by weight of Al ₂ O ₃ and 13 to 24% of MgO.
The wiring board according to claim 1, wherein the wiring board is composed of 20% by weight and 20 to 30% by weight of CaO. 3. The insulating substrate further contains a SiO ₂ crystal phase, has a coefficient of thermal expansion from room temperature to 400 ° C. of 8.5 ppm / ° C. or more, a dielectric constant of 7 or less, and 60 to 77 G
3. The wiring board according to claim 1, wherein the wiring board is made of a porcelain having a dielectric loss of 15 × 10 ⁻⁴ or less at Hz.