JP2005064436A - Glass ceramics wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide glass ceramics composed of SiO<SB>2</SB>-Al<SB>2</SB>O<SB>3</SB>-MgO-CaO based glass and Al<SB>2</SB>O<SB>3</SB>, and glass ceramics wiring board whose adhesion strength with a wiring conductor is high. <P>SOLUTION: The glass ceramics wiring board is constituted by laminating a plurality of insulating layers which contains SiO<SB>2</SB>-Al<SB>2</SB>O<SB>3</SB>-MgO-CaO based glass and Al<SB>2</SB>O<SB>3.</SB>In the glass ceramics wiring board wherein the wiring conductors whose principal component is silver are formed on surfaces of the insulating layers and between the layers, the wiring conductor contains glass containing SrO. As a result, wettability of interface between the wiring conductor and the glass ceramics composed of SiO<SB>2</SB>-Al<SB>2</SB>O<SB>3</SB>-MgO-CaO based glass and Al<SB>2</SB>O<SB>3</SB>is improved, and adhesion strength of the wiring conductor is improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a glass ceramic wiring board on which electronic components such as semiconductor integrated circuit elements such as IC and LSI and chip parts are mounted and wiring conductors for interconnecting them are formed.

  In recent years, semiconductor integrated circuit elements such as IC and LSI, chip parts, and the like have been reduced in size and weight, and a wiring board on which these are mounted is also desired to be reduced in size and weight. In response to these demands, multilayer ceramic substrates with internal electrodes formed in an insulating substrate can provide the required high-density wiring and can be thinned. Has been. As this multilayer ceramic substrate, a substrate made of an alumina sintered body and having a wiring conductor made of a refractory metal such as tungsten or molybdenum formed on the surface or inside thereof has been widely used.

  In addition, with the recent advanced information age, the frequency band used in semiconductor integrated circuit elements and the like is increasingly shifting to the high frequency band. In a high-frequency wiring board that transmits such a high-frequency signal, the electrical resistance of the conductor forming the wiring conductor is required to be small in order to transmit the high-frequency signal at high speed, and the insulating substrate also has a lower dielectric constant. Required.

  However, conventional refractory metals such as tungsten and molybdenum have a large conductor resistance and a large loss of electrical signals flowing in the wiring conductor (so-called conductor loss). It is also difficult to propagate the signal. Therefore, it is necessary to use a low-resistance metal such as copper, silver, or gold instead of a metal such as tungsten or molybdenum. However, since these low-resistance metals have a low melting point, it is necessary to fire at a low temperature of about 800 to 1000 ° C. when co-firing with an insulating substrate. It was not possible to co-fire with the alumina sintered body that needed to be fired. In addition, a multilayer ceramic substrate made of an alumina sintered body has a high dielectric constant, and is not suitable for a high-frequency circuit substrate.

  For this reason, recently, attention has been focused on using glass ceramics obtained by firing a mixture of glass and ceramics (inorganic filler) as an insulating substrate. In other words, glass ceramics are suitable as high-frequency insulating substrates because of their low dielectric constant, and glass ceramics can be fired at a low temperature of about 800 to 1000 ° C., so low resistance metals such as copper, silver, and gold Can be used as a wiring layer. When these low-resistance metals are used as wiring conductors, it is common to add glass to the wiring conductors in order to increase the adhesion strength between the wiring conductors and the glass ceramics.

  Among low-resistance metals such as copper, silver, and gold, silver has a low conductor resistance, and unlike copper, it can be fired in an oxidizing atmosphere, so the simultaneous firing technology with glass ceramics has already been studied and developed. As a result, the electrical characteristics of the multilayer ceramic substrate were greatly improved.

  However, multilayer ceramic substrates are increasingly being used in applications that require an electric signal of a large current of about 5 A or more, such as wiring substrates for ECUs (Electronic Control Units). In order to flow a large current through the mounted electronic component, it is necessary to make the diameter of the bonding wire connecting the wiring conductor and the electronic component very large, such as 100 μm or more. When such a bonding wire having a large diameter is to be connected to the wiring conductor by an ultrasonic bonder, it is necessary to generate a large friction energy between the bonding wire and the wiring conductor.

  In such a case, if silver is used as the wiring conductor, the silver does not easily react with the elements forming alumina, glass, etc. in the glass ceramic because the thermal energy released at the time of alloy formation is low. A sufficient bond between the conductor and alumina or glass cannot be obtained. As a result, there is a problem in that the adhesion strength between the wiring conductor and the glass ceramic is lowered, and peeling (so-called lift-off) occurs at the interface between the wiring conductor and the wiring substrate made of the glass ceramic.

  Therefore, as a means for solving the problem that the adhesion strength between the wiring conductor and the glass ceramic substrate is low, a silver / palladium conductor obtained by adding palladium or platinum to silver or a method using a silver / platinum conductor is generally used. This is because palladium and platinum have a high thermal energy released when forming an alloy, so that it is easy to react with the elements that form alumina, glass, etc. in glass ceramics, thus effectively improving adhesion strength. Depending on what can be done.

  Silver / palladium is frequently used as post-fire metallization by a thick film method in a composition having a palladium concentration of 5 to 30% by weight and silver / platinum in a composition having a platinum concentration of 0.1 to 5% by weight. In other words, post-fire by the thick film method means that after a conductive paste is printed on a fired glass ceramic substrate to form a pattern to be a wiring conductor, the conductor paste is baked at a temperature lower than the firing temperature of the glass ceramic substrate. Say.

Examples of the technique for forming the surface layer wiring by the post-fire by the thick film method include the following examples. Patent Document 1 discloses a conductive paste in which manganese oxide, chromium oxide, and glass frit are added to silver / palladium. Thereby, the effect of improving the adhesion strength after high-temperature aging of the surface layer wiring is obtained. Patent Document 2 discloses a conductive paste in which silicon dioxide and glass frit are added to silver. Thereby, the effect of improving the adhesion strength of the surface layer wiring is obtained.
JP-A-4-88067 Japanese Patent Publication No. 6-50705

  However, since the surface layer wirings in Patent Documents 1 and 2 are both based on post-fire by the thick film method, compared with simultaneous firing in which a ceramic sheet printed with a conductive paste serving as a wiring conductor is laminated and fired simultaneously. After the conductive paste is printed on the fired glass-ceramic substrate to form a pattern to be a wiring conductor, the process of baking the conductor paste at a temperature lower than the firing temperature of the glass-ceramic substrate is increased. There is a problem that defects such as adhesion of foreign matter are likely to occur, and the manufacturing cost is further increased.

  Further, since silver / palladium has a high conductor resistance, there is a problem that the conductor loss of the electric signal in the surface layer wiring is larger than that of the wiring conductor using silver as a conductor metal.

  The present invention has been completed in order to solve the above-mentioned problems of the prior art, and its purpose is to provide adhesion strength to glass ceramics even when a wiring conductor using silver as a conductive metal is used for the surface wiring. It is an object to provide an inexpensive glass-ceramic wiring board that is high, excellent in high-frequency characteristics, and has high wire bonding properties.

The glass-ceramic wiring board of the present invention is formed by laminating a plurality of insulating layers containing SiO ₂ —Al ₂ O ₃ —MgO—CaO-based glass and Al ₂ O ₃ , and mainly contains silver between the surface and the interlayer of the insulating layer. In the glass ceramic wiring board on which the wiring conductor as a component is formed, the wiring conductor contains glass containing SrO.

  The glass-ceramic wiring board of the present invention is preferably characterized in that the wiring conductor contains 0.5 to 15 parts by weight of the glass when silver is 100 parts by weight.

  The glass ceramic wiring board of the present invention is preferably characterized in that the maximum length of the glass phase contained in the wiring conductor is 1 to 10 μm.

In the glass ceramic wiring board of the present invention, the SrO in the glass contained in the wiring conductor is an interface contact between the wiring conductor and a glass ceramic composed of SiO ₂ —Al ₂ O ₃ —MgO—CaO glass and Al ₂ O _3. Since the corners are reduced and the wettability is improved, the work of adhesion of the wiring conductor, the glass ceramic composed of SiO ₂ —Al ₂ O ₃ —MgO—CaO glass and Al ₂ O ₃ , that is, the bonding force increases, As a result, the adhesion strength can be improved.

Further, when the content of the glass containing SrO in the wiring conductor is 0.5 to 15 parts by weight with respect to 100 parts by weight of the wiring conductor, the wiring conductor, the SiO ₂ —Al ₂ O ₃ —MgO—CaO-based glass, and Al The adhesion strength with the glass ceramic made of ₂ O ₃ can be further improved, and the occurrence of defective plating formation due to the glass being raised on the surface of the wiring conductor during firing can be suppressed.

Further, when the maximum length of the glass phase contained in the wiring conductor is 1 to 10 μm, the wiring conductor and the glass ceramic made of SiO ₂ —Al ₂ O ₃ —MgO—CaO-based glass and Al ₂ O ₃ are adhered to each other. Strength can be further strengthened. For this reason, when conducting a wire conductor strength test using a wire with a large diameter, when the strength test is performed on the wiring conductor, there is a problem from the viewpoint of mounting reliability. Occurrence of breakage in the conductor can be prevented.

As a result, it is possible to effectively improve the adhesion strength between the wiring conductor and the glass ceramic composed of SiO ₂ —Al ₂ O ₃ —MgO—CaO-based glass and Al ₂ O _3. Sex can be obtained.

  The glass ceramic wiring board of the present invention will be described in detail below.

The glass ceramic green sheet used as the insulating substrate of the glass-ceramic wiring board of the present invention uses a glass powder and filler (ceramic powder) as a glass component and further mixed with an organic binder, plasticizer, organic solvent, etc. It is done. The glass component is SiO ₂ —Al ₂ O ₃ —MgO—CaO-based glass, which is preferably crystallized glass that crystallizes during firing. By using such a glass component, the mechanical strength of the glass ceramic can be improved by crystallizing the glass after firing. The filler is Al ₂ O ₃ .

  The mixing ratio of these glass components and fillers is preferably 40:60 to 99: 1 by mass ratio. If the glass component is less than 40% by mass, the firing temperature of the glass ceramic becomes high, and low resistance metals such as copper, silver and gold cannot be used as the wiring conductor. When the glass component exceeds 99% by mass, the filler cannot fulfill the function of maintaining the shape of the glass ceramic, and a glass ceramic having a desired shape cannot be obtained after firing.

  As the organic binder blended in the glass ceramic green sheet, those conventionally used in ceramic green sheets can be used, for example, acrylic type, and single weight of acrylic acid, methacrylic acid or esters thereof. A polymer or a copolymer, specifically, an acrylic ester copolymer, a methacrylic ester copolymer, an acrylic ester-methacrylic ester copolymer, or the like. Moreover, homopolymers or copolymers such as polyvinyl butyral, polyvinyl alcohol, acryl-styrene, polypropylene carbonate, and cellulose are listed.

  The glass ceramic green sheet is obtained by adding a predetermined amount of plasticizer and solvent (organic solvent, water, etc.) to the above glass powder, filler powder, and organic binder as necessary to obtain a slurry. It can be obtained by molding to a thickness of about 50 to 500 μm by a calender roll method, a die press method or the like.

  In order to form the pattern of the wiring conductor on the surface of the glass ceramic green sheet, for example, a method of printing a conductor paste obtained by pasting a powder of a conductor material by a screen printing method, a gravure printing method or the like can be used. As the conductor material, silver is preferable because it can be fired in the air and has a low conductor resistance. Silver may contain trace amounts of elements such as iron, cobalt, copper, platinum, and palladium.

The conductor paste contains glass containing at least SrO. Although details of the influence of SrO contained in the glass on the contact angle between the wiring conductor and the glass ceramics are not clear, SrO in the glass contained in the wiring conductor is composed of the wiring conductor and SiO ₂ —Al ₂ O ₃ —MgO. -It works to reduce the contact angle at the interface with the glass ceramics made of CaO-based glass and Al ₂ O ₃ and improve the wettability. For this reason, the work of adhesion between the wiring conductor and the glass ceramic made of SiO ₂ —Al ₂ O ₃ —MgO—CaO-based glass and Al ₂ O ₃ is increased, and as a result, the adhesion strength can be improved. It is done.

  Here, the work of adhesion is the energy per unit area required to peel off the interface on which the dissimilar material is adhered, the work of adhesion is W, the surface energy of silver is γ, and the interface between the silver and glass ceramics. When the contact angle is θ, the relationship W = γ (1 + cos θ) is established.

In the present invention, the wiring conductor preferably contains 0.5 to 15 parts by weight of glass when silver is 100 parts by weight. In this case, the wiring conductor and SiO ₂ —Al ₂ O ₃ —MgO reinforce the adhesion strength between the glass ceramic consisting -CaO based glass and Al ₂ O _3, and it is possible to suppress the relief defective plating film formation by on the wiring conductor surface of the glass during firing.

When the content of the glass containing SrO is less than 0.5 parts by weight with respect to 100 parts by weight of silver, SrO in the glass is composed of the wiring conductor, the SiO ₂ —Al ₂ O ₃ —MgO—CaO-based glass, and Al ₂ O _3. The effect of reducing the contact angle at the interface with the resulting glass ceramic is not expressed, and the adhesion strength between the wiring conductor and the glass ceramic made of SiO ₂ —Al ₂ O ₃ —MgO—CaO glass and Al ₂ O ₃ is improved. I can't. In addition, when the content of the glass containing SrO exceeds 15 parts by weight with respect to 100 parts by weight of silver, defective plating formation occurs due to the glass being raised on the surface of the wiring conductor during firing, resulting in poor aluminum wire bonding. cause.

In the present invention, the maximum length of the glass phase contained in the wiring conductor is preferably 1 to 10 μm. In this case, the wiring conductor, the SiO ₂ —Al ₂ O ₃ —MgO—CaO-based glass, and Al _{2 are used.} The adhesion strength with the glass ceramic made of O ₃ can be further strengthened. For this reason, when conducting a wire conductor strength test using a wire with a large diameter, when the strength test is performed on the wiring conductor, there is a problem from the viewpoint of mounting reliability. Occurrence of breakage in the conductor can be prevented.

  When the maximum length of the glass phase contained in the wiring conductor is larger than 10 μm, it is difficult to uniformly disperse the glass phase in the wiring conductor, which is effective in improving the strength of the wiring conductor-glass ceramics interface. The anchor effect of glass does not appear stably, and it is difficult to further improve the strength.

  Further, when the maximum length of the glass phase is less than 1 μm, the glass phase length existing at the wiring conductor-glass ceramics interface is reduced, so that the anchor effect of the glass at the wiring conductor-glass ceramics interface is reduced, It is difficult to further improve the strength.

  As a method of setting the maximum length of the glass phase contained in the wiring conductor to 1 to 10 μm, there is a method of setting the content of glass contained in the wiring conductor to 0.5 to 15 parts by weight with respect to 100 parts by weight of silver. . When the content of the glass contained in the wiring conductor is 0.5 to 15 parts by weight with respect to 100 parts by weight of silver, the glass component contained in the wiring conductor is appropriately sintered between the glass components when the glass ceramic substrate is fired. The maximum length is 1 to 10 μm. When the glass content is less than 0.5 parts by weight with respect to 100 parts by weight of silver, since the glass components are less likely to be sintered, the maximum length of the glass phase contained in the wiring conductor is smaller than 1 μm. . Conversely, when the glass content exceeds 15 parts by weight with respect to 100 parts by weight of silver, the maximum length of the glass phase contained in the wiring conductor is larger than 10 μm because the sintering of the glass components proceeds excessively. Become.

  Further, the wiring conductor includes a portion where a through conductor such as a via hole or a through hole for connecting the wiring conductors between the upper and lower glass ceramic layers is exposed on the surface. These through conductors are formed by means such as embedding by printing a conductive paste obtained by pasting a conductive material powder into a through hole formed in a glass ceramic green sheet by punching or the like.

  For the lamination of glass ceramic green sheets, heat and pressure are applied to the stacked glass ceramic green sheets by thermocompression bonding, or an adhesive consisting of organic binder, plasticizer, solvent, etc. is applied between the glass ceramic green sheets. A method such as thermocompression bonding can be employed.

  After laminating the glass ceramic green sheets, the organic components are removed and fired. The organic component is removed by heating the laminate in the temperature range of 100 to 800 ° C. to decompose and volatilize the organic component. Moreover, although a calcination temperature changes with glass ceramic compositions, it exists in the range of about 800-900 degreeC. Some general glass ceramic materials are fired at 900 ° C. or higher. However, in the present invention, the wiring conductor is fired at the same time. Therefore, the range of 800 to 900 ° C. is preferable according to the firing temperature of the wiring conductor. When fired at a temperature exceeding 900 ° C., the electrical characteristics deteriorate due to an increase in the electrical resistance value of the wiring conductor, and the mechanical strength deteriorates due to oversintering of the glass ceramic. The firing is performed in the air.

  Further, during firing, a load may be applied by placing a weight on the upper surface of the glass ceramic green sheet laminate in order to prevent warping. The load should be about 50-1 MPa. When the load is less than 50 Pa, the action of suppressing the warp of the glass ceramic green sheet laminate may not be sufficient. Further, when the load exceeds 1 MPa, the weight to be used increases, so that there is a risk that it will not enter the firing furnace, or even if it enters the firing furnace, the heat capacity will be insufficient and firing will not be possible. As the weight, for example, porous ceramics, metal, or the like is preferably used so as not to prevent the dissociation of the decomposed organic component. Further, a porous weight may be placed on the upper surface of the glass ceramic green sheet laminate, and a non-porous weight may be placed thereon.

  After firing, a glass ceramic wiring board capable of aluminum wire bond mounting can be obtained by forming a plating film of nickel, gold or the like having a thickness of about 0.1 to 10 μm on the wiring conductor.

  Examples of the glass ceramic wiring board of the present invention will be described below.

(Example 1)
First, glass ceramics composed of 70 parts by weight of SiO ₂ —Al ₂ O ₃ —MgO—CaO-based crystallized glass powder and 30 parts by weight of Al ₂ O ₃ powder was used as the glass ceramic substrate.

Next, as a wiring conductor to be formed on this glass ceramic substrate, SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —MgO—CaO—BaO—SrO-based glass (glass A) is added to 0.25 to 100 parts by weight of silver. A glass ceramic wiring board on which this wiring board was formed was prepared using 20 parts by weight.

As a comparative example, SrO-free SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —MgO—CaO—BaO-based glass (glass B) is contained in an amount of 0.25 to 20 parts by weight with respect to 100 parts by weight of silver. The glass ceramic wiring board on which this wiring board was formed was produced by the same method as in the case of glass A.

When a 4 μm thick Ni plating film and a 1 μm thick Au plating film are formed on the wiring conductor on the surface of these glass ceramic wiring boards, and then a 300 μm diameter aluminum wire is bonded on the wiring conductor Table 1 shows the results of examining the probability of lift-off (wire disconnection).

  From Table 1, in the glass containing SrO which is an example of the present invention, the lift-off rate is lower than the glass containing no SrO, and the addition amount of the glass containing SrO is 0.5 to 15 parts by weight. No lift-off occurred at all.

(Example 2)
By changing the maximum length and addition amount of the glass phase and measuring the strength per unit area of the wiring conductor of the glass ceramic substrate produced by the same method as in Example 1, the strength value and the mode of destruction It shows in Table 2.

  From Table 2, when the maximum length of the glass phase is set to 1 to 10 μm, it is considered that there is a problem in mounting reliability when wire bond mounting is performed using a wire having a large diameter. There was no breakage or breakage in the wiring conductor.

  The present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the gist of the present invention.

Claims (3)

A plurality of insulating layers including SiO ₂ —Al ₂ O ₃ —MgO—CaO-based glass and Al ₂ O ₃ were laminated, and a wiring conductor mainly composed of silver was formed on the surface and between the insulating layers. In the glass ceramic wiring board, the wiring conductor contains glass containing SrO. 2. The glass ceramic wiring board according to claim 1, wherein the wiring conductor contains 0.5 to 15 parts by weight of the glass when silver is 100 parts by weight. The glass ceramic wiring board according to claim 1, wherein the maximum length of the glass phase contained in the wiring conductor is 1 to 10 μm.