JP2006222307A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board having an insulating layer made thin to have a thickness ≤100 μm and exhibiting high insulation, even if it is subjected to plating treatment. <P>SOLUTION: This wiring board is composed of an insulating board comprising a plurality of laminated insulating layers and formed with a wiring layer at least on the surface of the insulating board, and the surface of the insulating board is composed of a glass ceramic sintered substance with a thickness of ≤100 μm containing glass and a crystal phase. The areal occupation rate of voids at the cross section of the insulating board is ≤3%, and the weight reduction thereof upon one minute immersion in a 1 mass% HF aqueous solution is ≤3 μg/mm<SP>2</SP>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wiring board used in an electrical element storage package, a hybrid integrated circuit device, or the like.

  The rapid development of information communication technology in recent years has led to higher frequencies used, and in wiring boards used for information communication applications, in order to reduce transmission loss of high-frequency signals, lower resistance and insulation of the wiring layer There is a demand for a low dielectric constant of the layer. Therefore, a wiring board having a glass ceramic sintered body that can be densified by firing at 1000 ° C. or less and can be simultaneously fired with a wiring layer mainly composed of a low-resistance metal such as gold, silver, or copper is used as an insulating layer. Proposed.

  Furthermore, these wiring boards are extremely demanded for high density, small size, and light weight, and the demand is particularly strong in wiring boards mounted on portable information communication devices represented by mobile phones. . In response to such demands for higher density and smaller size and weight, it has been proposed to reduce the thickness of the insulating layer constituting the wiring board, particularly for the demand for lower height. As a result, a problem arises in that the insulating properties are lowered due to the thin insulating layer.

Therefore, the thickness of each insulating layer is reduced to 100 μm or less, and at the same time, the maximum crystallite diameter is controlled to 5 μm or less, the void area ratio of the insulating layer is controlled to 3% or less, and the maximum void diameter is controlled to 5 μm or less. It is disclosed that the insulating property is improved to 10 ¹¹ Ω · cm or more by using glass ceramics (see, for example, Patent Document 1).
JP 2004-235347 A

  However, the insulating layer described in Patent Document 1 forms a plating film on the surface wiring layer after co-firing with a wiring layer made of a low-resistance metal. Since the plating solution penetrates and the metal as the plating component is deposited inside the insulating layer, there is a problem that the insulation between the wiring layers sandwiching the insulating layer on the surface is lowered, and a short circuit or the like occurs.

  Accordingly, an object of the present invention is to provide a wiring board that exhibits high insulation even when the thickness of the insulating layer is reduced to 100 μm or less and plating is performed.

The wiring board of the present invention comprises an insulating substrate formed by laminating a plurality of insulating layers, and has a wiring layer on at least the surface of the insulating substrate, and the insulating substrate disposed on the surface of the insulating substrate. When the layer is made of a glass ceramic sintered body containing glass and a crystalline phase and having a thickness of 100 μm or less, the void area occupancy in the cross section of the insulating substrate is 3% or less, and when immersed in a 1% by mass HF aqueous solution for 1 minute The weight loss is 3 μg / mm ² or less.

  In particular, among the voids, the area occupied by the substantially spherical voids is preferably 75% or more of the whole. Thereby, there exists an advantage that the osmosis | permeation of plating solution can be suppressed more effectively.

  Among the voids, it is preferable that the occupied area of the voids present in isolation is 75% or more of the whole. Thereby, it is possible to more effectively suppress the penetration of the plating solution.

  It is preferable that the glass ceramic sintered body does not substantially contain an alkali metal oxide. Thereby, there exists an advantage that the insulation of an insulating layer can be improved.

The electrical resistance in the thickness direction of the insulating layer disposed on the surface is preferably 10 ⁹ Ω / mm ² or more. Thereby, there exists an advantage that the insulation of the thickness direction of an insulating layer can be ensured.

  The wiring layer preferably contains at least one of gold, silver and copper as a main component. This has an advantage that a low-resistance wiring can be formed.

  It is preferable that a plating layer is deposited on the surface of the wiring layer disposed on the surface of the insulating substrate. Thereby, there is an advantage that solder wettability and oxidation resistance of the wiring layer can be ensured.

  Since the present invention performs a surface treatment using an acid as a pretreatment for the plating treatment, the glass component is eluted from the insulating glass ceramics constituting the insulating layer immersed in the acid solution, and the solution penetrates into the insulating layer. It was made based on the novel knowledge that a fine space is formed, the plating solution penetrates into the insulating layer from the space, and the metal is deposited inside the insulating layer, resulting in a decrease in insulation. In addition, by using insulating glass ceramics with high acid resistance, a high insulating property is realized even when a wiring substrate having a thickness of an insulating layer disposed on the surface of 100 μm or less is plated.

That is, when the insulating layer is thick, even if the plating solution penetrates into the insulating layer and the metal is deposited, there is a sufficient insulation distance from the internal electrode, so there is no short circuit, but the insulating layer is 100 μm. Hereinafter, particularly when the thickness is reduced to 50 μm or less, and further to 30 μm or less, the insulation distance is shortened and short-circuited. This is because the insulating glass ceramic is eluted by chemical treatment performed as a pretreatment for plating. And found that the void area occupancy of the insulating layer is 3% or less, and the weight loss when immersed in a 1% by mass HF aqueous solution for 1 minute is 3 μg / mm ² or less, thereby maintaining high insulation. can do.

  Hereinafter, a wiring board of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of a hybrid integrated circuit device using the wiring board of the present invention.

  In FIG. 1, a wiring board A is composed of an insulating substrate 1 formed by laminating a plurality of insulating layers 1a to 1e, and the surface and interface of each insulating layer are low in the main component of gold, silver or copper. A wiring layer 2 made of a resistance metal is formed. A via-hole conductor 3 for electrically connecting the wiring layer 2 is formed so as to penetrate the insulating layers 1a to 1e, and the via-hole conductor 3 is any one of gold, silver, copper, and the like. It consists of a low resistance metal whose main component is. Furthermore, a plurality of connection electrodes 4A are arranged on the lower surface of the wiring board A, and the connection electrodes 4A are connected to the connection electrodes 4B of the external circuit board B such as a printed circuit board by solder 9 or the like. .

  Various electronic components 5 such as semiconductor elements such as Si and GaAs, SAW devices and capacitors are bonded and fixed to the surface of the wiring board A via an adhesive 10 such as glass or an underfill agent or solder 8. The surface of 5 is sealed with a sealing resin 6 made of a potting agent or the like. In addition, the electronic component 5 is electrically connected to the wiring layer 2 via the wire bonding 7, solder 8, and the like.

  The wiring board of the present invention is characterized in that the insulating layer 1a disposed on the surface is made of a glass ceramic sintered body having a thickness of 100 μm or less, including glass and a crystal phase. In order to further reduce the height of the insulating layer 1a, it is preferably 50 μm or less, particularly preferably 30 μm or less.

  According to the present invention, in order to improve the insulation of a thin insulating layer having a thickness of 100 μm or less, the void area occupation ratio (hereinafter simply referred to as void ratio) in the cross section of the insulating substrate is 3% or less. Is important, and is preferably 2.5% or less, more preferably 2% or less.

  When the void ratio exceeds 3%, the voids are easily connected to each other. When such a connected void is present on the surface, the acid enters the inside of the void, and the void further expands to the inside. Since the plating film is formed inside the insulating layer, the insulating property of the insulating layer may be lowered.

  In addition, since a similar phenomenon occurs even when a large void exists on the surface, it is important to remove the large void by proceeding with densification to reduce the void ratio to 3% or less. In particular, it is preferable that the average diameter of the voids is 5 μm or less, further 3 μm or less, and more preferably 2 μm or less.

  In addition, the average diameter of the void in the present invention is calculated by converting the cross-sectional area of the void into a circle and using the diameter as the average diameter.

  According to the present invention, among the voids included in the insulating substrate, the area occupied by the substantially spherical voids is preferably 75% or more, particularly 80% or more, and more preferably 85% or more. If the shape of the void is substantially spherical, a plurality of voids are difficult to combine three-dimensionally. By setting the occupied area of such a spherical void in the above range, the plating solution penetrates into the insulating layer. Can be more effectively suppressed and high insulation can be maintained.

  In addition, among the voids included in the insulating substrate, it is preferable that the occupied area of the isolated voids is 75% or more, particularly 80% or more, and more preferably 85% or more. If voids exist in isolation, even if the plating solution enters the inside of the void, the depth is almost the same as the diameter of the void, which suppresses plating solution penetration more effectively and maintains high insulation. it can.

Further, according to the present invention, it is also important that the weight loss when immersed in a 1% by mass aqueous HF solution for 1 minute is 3 μg / mm ² or less, particularly 2.5 μg / mm ² or less, and further 2 μm / mm. It is preferable that it is ² or less. Reducing the weight loss when immersed in a 1% by mass HF aqueous solution for 1 minute means that the elution of the glass component from the glass ceramic sintered body constituting the insulating layer is suppressed. It is possible to more effectively suppress the penetration of the plating solution into the insulating layer and maintain high insulation.

On the other hand, when the weight loss is larger than 3 μg / mm ² , the glass component is eluted from the glass ceramic sintered body constituting the insulating layer, and a fine space into which the solution permeates is formed inside the insulating layer. The plating solution also penetrates into the insulating layer from the space, and as a result of the metal depositing inside the insulating layer, there is a possibility that the insulating property is greatly impaired.

HF is a chemical generally used in a glass etching process for removing glass existing on the wiring layer before the plating process, and has a function of dissolving glass containing SiO ₂ .

According to the present invention, the electrical resistance in the thickness direction of the insulating layer disposed on the surface of the wiring board is 10 ⁹ Ω / mm ² or more, particularly 10 ¹⁰ Ω / mm ² or more, more preferably 10 ¹¹ Ω / mm ² or more. It is preferable that This makes it easy to ensure insulation in the thickness direction of the insulating layer after plating. Specifically, the electrical resistance in the thickness direction of the insulating layer after plating is set to 10 ⁹ Ω / mm ² or more. Can do.

  The glass ceramic sintered body used in the present invention contains glass and a crystalline phase. Acid resistance can be improved by containing a crystal phase and increasing the amount thereof.

The glass contained in the glass ceramic sintered body contains at least SiO ₂ , a tetravalent metal oxide such as ZrO ₂ , TiO ₂ , SnO ₂ , Al ₂ O ₃ , B ₂ O ₃ , Y ₂ O ₃ , It is preferable to include at least one of trivalent metal oxides such as La ₂ O ₃ , alkaline earth oxides (hereinafter referred to as MO), divalent metal oxides such as ZnO and PbO, and transition metal oxides. By adjusting these combinations, high insulating properties can be maintained even when acid treatment is performed.

For example, borosilicate glass or Bi glass such as SiO ₂ —B ₂ O ₃ glass, SiO ₂ —B ₂ O ₃ —MO glass, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —MO glass, etc. Etc. can be illustrated.

Among these, it is preferable to employ SiO ₂ —B ₂ O ₃ —MO-based glass because it is easy to control softening characteristics suitable for firing at low temperature, and more excellent acid resistance. In view of the above, it is desirable to further contain Al ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ or the like, and it is particularly desirable to contain Al ₂ O ₃ .

In consideration of environmental harmony, it is desirable that the glass does not substantially contain harmful substances such as PbO, As ₂ O ₃ , CdO, and Hg. “Substantially not contained” means not intentionally contained, and a trace amount of inevitable impurities is not limited to this.

  The crystalline phases contained in the sintered glass ceramic include alumina, zirconia, quartz, cristobalite, cordierite, mullite, spinel, garnite, enstatite, forsterite, anorsite, slausonite, serdian, diopside, and montcelite. , Akermanite, willemite, silicon nitride, aluminum nitride, silicon carbide, boron carbide and its solid solutions, substituted derivatives, and the like.

  Of these crystal phases, it is preferable to employ alumina, zirconia, forsterite, enstatite, spinel, anorthite, slusonite, and serdian, particularly alumina, zirconia, and forsterite in terms of improving the bending strength. . In terms of improving acid resistance, alumina, zirconia, forsterite, enstatite, spinel, anorthite, slausonite, serdian, cordierite are preferable, and alumina and zirconia are particularly preferable.

  Furthermore, forsterite, enstatite, quartz, cristobalite, cordierite, and mullite are preferred to lower the dielectric constant and reduce transmission loss of high-frequency signals, and in particular, forsterite, quartz, and cordierite are preferred. preferable. Furthermore, in order to improve thermal conductivity, alumina, silicon nitride, aluminum nitride, and silicon carbide are preferable, and aluminum nitride is particularly preferable.

  By appropriately combining these glasses and crystalline phases, it is possible to control the ceramic properties, thermal properties, dielectric properties and other porcelain properties of the glass ceramic sintered body according to the application.

  Further, it is desirable for the glass ceramic sintered body to contain substantially no alkali metal oxide, particularly lithium oxide, in order to ensure high insulation. This is a component in which the alkali metal oxide may lower the insulating property of the glass phase as a conductive carrier, and in particular, by excluding lithium oxide, it becomes easy to maintain the insulating property of the insulating layer. .

  “Substantially not contained” means not intentionally contained, and a trace amount of inevitable impurities is not limited to this.

  In order to reduce the transmission loss of the high frequency signal, it is desirable that the wiring layer 2 formed on the surface of the wiring board is mainly composed of at least one of gold, silver and copper low resistance metals.

  Furthermore, in order to ensure the solder wettability and oxidation resistance of the surface wiring layer, a plating layer of Ni, Au, Cu or the like is deposited on the surface of the wiring layer disposed on the surface of the wiring substrate. It is desirable that

  By adopting such a configuration of the wiring board of the present invention, even if the thickness of the insulating layer 1a disposed on the surface is reduced to 100 μm or less, high insulation can be ensured after the plating process.

  Next, a method for manufacturing the wiring board shown in FIG. 1 will be described.

  First, glass powder and optionally ceramic powder are prepared as raw powder.

  As the glass powder, the glass described above is preferably used. At this time, either an amorphous glass that does not crystallize during firing or a crystallized glass that crystallizes during firing may be used. However, in order to develop a high bending strength and a low dielectric loss, a crystal can be used. It is desirable to use a vitrified glass.

  On the other hand, as the ceramic powder, those having the above-mentioned crystal phase are preferably used, but in addition to this, amorphous powder such as quartz glass can be used.

  As for the particle size of these raw material powders, in order to achieve a low void ratio, the average particle size (D50) is 5.0 μm or less, particularly 3.5 μm or less, further 2.5 μm or less, and optimally 2. It is desirable that it is 0 μm or less.

  Further, in order to make the shape of the void substantially spherical and to isolate each void, the difference in the particle size distribution between the glass powder and the ceramic powder is reduced, that is, the difference in the average particle size (D50) is ± 1 μm or less. In particular, it is effective to make it as small as ± 0.5 μm or less.

  Further, in order to ensure high insulation, the alkali metal oxide is substantially contained in the glass powder and the ceramic powder so as not to substantially contain the alkali metal oxide in the glass ceramic sintered body. It is desirable not to contain it.

  A molding slurry is prepared by using a mixed powder obtained by appropriately mixing glass powder and ceramic powder in a certain quantitative ratio as described above, and using this molding slurry, for example, a ceramic green sheet having a thickness of 25 to 500 μm ( Sheets for insulating layers 1a to 1e) are formed.

  A through hole is formed at a predetermined position of the green sheet, and a conductor paste mainly composed of a low resistance metal such as copper, silver, or gold is filled in the through hole, thereby forming a via hole conductor 3. Further, the surface of the green sheet corresponding to the insulating layer on which the wiring layer 2 is formed on the surface or the interface is wired using the above-described conductor paste by a known printing method such as a screen printing method or a gravure printing method. A wiring pattern is printed and applied so that the thickness of the layer 2 is 2 to 30 μm.

  Then, the plurality of green sheets prepared as described above were aligned and laminated and pressure-bonded, and then subjected to binder removal treatment at a temperature of 450 to 750 ° C. in the atmosphere or in a nitrogen atmosphere containing water vapor. Then, the insulating substrate 1 provided with the wiring layer 2 and the via-hole conductor 3 is manufactured by firing in the air at 1000 ° C. or lower or in a nitrogen atmosphere.

  Note that the binder removal atmosphere and firing atmosphere are appropriately determined according to the type of low-resistance metal used. For example, when copper is used as the wiring conductor, it is oxidized by firing in the air. Binder removal or firing is performed.

  An electronic component 5 such as a semiconductor element is mounted on the surface of the insulating layer 1 formed as described above, and is connected to the wiring layer 2 so that signals can be transmitted. As described above, the electronic component 5 can be directly mounted on the wiring layer 2 and can be connected by solder 8 or the like. Alternatively, the wire bonding 7 can be used to connect the electronic component 5 and the surface of the insulating layer 1. The wiring layer 2 can also be connected. It is also possible to connect the two by flip chip connection or the like.

  Furthermore, the sealing resin 6 is applied to the surface of the insulating layer 1 on which the electronic component 5 is mounted and cured, or the insulating material of the same type as the insulating layer 1, other insulating materials, or a metal with good heat dissipation, etc. The electronic component 5 can be hermetically sealed by bonding the lid made of the above with an adhesive such as glass, resin, or brazing material, whereby the wiring board A can be manufactured. Further, if necessary, various heat sinks can be attached to the wiring board A via a brazing material or an adhesive.

The wiring board of the present invention thus produced is an insulating board formed by laminating a plurality of insulating layers, and has a wiring layer on at least the surface of the insulating board, and the surface of the insulating board The insulating layer disposed on the substrate is made of a glass ceramic sintered body having a glass and a crystal phase and a thickness of 100 μm or less, and the void area occupancy in the cross-section of the insulating substrate is 3% or less. By setting the weight loss when immersed for 1 minute to 3 μg / mm ² or less, high insulation can be ensured even after the plating treatment.

First, glass powder having the composition shown in Table 1 is prepared, glass powder and ceramic powder having different particle diameters (D50) are weighed and mixed according to Table 2, and a binder made of an acrylic resin, a plasticizer, and toluene are mixed into this mixture. Was added to prepare a slurry, and a sheet-like molded body was prepared using the slurry by a doctor blade method so that the thickness after firing was 15 to 100 μm.

  Next, after forming a via hole at a predetermined position of the sheet-like molded body and filling a conductor paste mainly composed of copper, the sheet-like molded body is formed using the conductor paste mainly composed of copper by a screen printing method. A wiring pattern having a thickness of 5 μm after firing was formed on the surface.

  Then, while aligning the sheet-like molded body on which the wiring pattern was formed, a plurality of sheets were laminated and thermocompression bonded to produce a raw insulating substrate before firing. At this time, a sheet-like molded body having a thickness shown in Table 3 was disposed on the surface of the raw insulating substrate.

During this raw laminated _{N 2} / _H 2 O atmosphere, after binder removal treatment at 700 ° C., the temperature was raised at 200 ° C. / _time, in N ₂ / _H 2 O atmosphere, copper and calcined 1 hour at 900 ° C. A wiring substrate made of an insulating substrate having a wiring layer as a main component was produced, and Ni-Au plating including HF aqueous solution treatment was applied as a pretreatment. The plating thickness at this time was set to Ni: 3 μm and Au: 0.5 μm.

  In this way, a wiring board having a thin insulating layer having a wiring layer with Ni—Au plating on the surface layer was prepared.

  Here, the insulation resistance of the thin insulating layer having the wiring layer with the Ni—Au plating on the surface layer is used by using 30 wiring pads facing the insulating layer in the thickness direction and having a size of 1 mm □. It was measured. Table 2 shows the minimum measurement results.

  On the other hand, without forming a wiring layer and a via hole in the sheet-like molded body, lamination and thermocompression bonding were performed in the same manner as described above to produce a glass ceramic sintered body consisting only of an insulating layer.

  The obtained sintered body was mirror-polished, a scanning electron microscope (SEM) photograph was taken, and the void ratio was calculated using an image analyzer. Further, from the SEM photograph, the area of substantially spherical voids and isolated voids and the area of all voids were measured, and the area ratio of substantially spherical voids and the area of isolated voids were calculated. The results are shown in Table 2.

This glass ceramic sintered body is immersed in a 1% by mass HF aqueous solution for 1 minute, the weight change before and after that is measured, and normalized by the surface area, thereby reducing the weight when immersed in a 1% by mass HF aqueous solution for 1 minute. Was measured. The results are shown in Table 2.

Sample No. which is the wiring board of the present invention. 2 to 14, the void area occupancy in the cross section of the insulating substrate is 3% or less, and the weight loss when immersed in a 1% by mass HF aqueous solution for 1 minute is 3 μg / mm ² or less, so that even after plating. The electric resistance in the thickness direction of the insulating layer disposed on the surface of the insulating substrate showed a high insulating property of 10 ⁹ Ω / mm ² or more.

Among them, sample No. ² using C glass, having a void ratio of 2% or less and a weight loss of 2 μg / mm ² or less when immersed in a 1% by mass HF aqueous solution for 1 minute. Nos. 5 to 13 were particularly excellent in insulation with an electric resistance of 10 ¹¹ Ω / mm ² or more.

On the other hand, in the cross section of the insulating substrate, the sample area No. in which the void area ratio and the weight loss when immersed in a 1 mass% HF aqueous solution for 1 minute are larger than the range of the present invention. In No. 1, there was much penetration of the plating solution into the insulating layer, and the electric resistance in the thickness direction of the insulating layer disposed on the surface of the insulating substrate was lower than 10 ⁹ Ω / mm ² .

It is a schematic sectional drawing which shows the structure of the wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... Wiring layer 3 ... Via-hole conductor 4 ... Connection electrode 5 ... Electronic component 6 ... Sealing resin 7 ... Wire bonding 8 ... Solder 9 ... Solder 10 ... Adhesive A ... Wiring board B ... Printed circuit board

Claims (7)

A wiring board comprising a plurality of insulating layers laminated and having a wiring layer on at least a surface of the insulating board, the surface of the insulating board including glass and a crystal phase, and a thickness of 100 μm or less The void area occupancy in the cross section of the insulating substrate is 3% or less, and the weight loss when immersed in a 1% by mass HF aqueous solution for 1 minute is 3 μg / mm ² or less. Wiring board. 2. The wiring board according to claim 1, wherein an area occupied by substantially spherical voids is 75% or more of the voids. 3. The wiring board according to claim 1, wherein an occupied area of the voids isolated from the voids is 75% or more of the whole. 4. The wiring substrate according to any one of claims 1 to 4, wherein the glass ceramic sintered body does not substantially contain an alkali metal oxide. The wiring substrate according to claim 1, wherein an electrical resistance in a thickness direction of the insulating layer disposed on the surface is 10 ⁹ Ω / mm ² or more. The wiring board according to claim 1, wherein the wiring layer contains at least one of gold, silver, and copper as a main component. The wiring board according to claim 1, wherein a plating layer is deposited on the surface of the wiring layer disposed on the surface of the insulating substrate.

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