JP4571853B2 - Wiring board - Google Patents

Description

  The present invention relates to a wiring board in which conductor pins are brazed to a Cu metallized layer formed on at least one of a front surface and a back surface of a substrate body made of glass-ceramic.

A wiring board including a low-dielectric loss glass-ceramic substrate body and a low-resistance Cu metallization layer formed on at least one of the front and back surfaces of the substrate body is mounted on an electronic component used in a high-frequency region. Suitable for use. Furthermore, by brazing a conductor pin to the Cu metallized layer, it can be widely used for mounting an MPU, for example, an optical communication field in which an optical communication element is mounted.
By the way, when the conductor pin is brazed to the Cu metallized layer formed on the back surface of the substrate body made of, for example, glass-ceramic via a Sn—Sb brazing material having a low melting point (about 220 ° C.), the substrate At the time of reflow when mounting an electronic component on the surface of the main body via an Sn-Ag alloy having a melting point higher than that of the brazing material, there is a problem that the brazing material softens or melts and the conductor pin falls down. .
Moreover, since the adhesion between the glass-ceramic of the substrate main body and the Cu metallized layer is low, the conductivity between the internal wiring of the substrate main body and the metallized layer is reduced, or the metallized layer is peeled off to form a conductor pin. There was also a problem that was accidentally removed.

On the other hand, above the thin film pad made of Ti / Mo / Ni ₃ Mo or the like located on the surface of the glass ceramic substrate, it is made of 42 alloy through the brazing material of Ag—Cu eutectic alloy or Ag—Sn alloy. A multilayer wiring board in which input / output pins are brazed has been proposed (see, for example, Patent Document 1).
In addition, an Ag—Sn or Ag—Si alloy brazing material is placed on the nail head portion through the Ni plating layer and the Au rich layer on the Cu connection pad located on the lower surface of the insulating base made of glass ceramic. There has also been proposed a ceramic package with a lead pin in which the lead pin provided in is brazed with such a brazing material (see, for example, Patent Document 2).

JP-A-8-298381 (pages 1-6, FIG. 1) JP 2003-224224 A (pages 1 to 9, FIGS. 1 and 2)

  However, when brazing the above-mentioned Cu metallized layer formed on the glass-ceramic substrate body using an Ag-Cu eutectic alloy, the brazing metal is near the melting point of the Ag-Cu eutectic alloy. The difference in coefficient of thermal expansion among the three members, the material, the glass-ceramic substrate body, and the Cu metallized layer is increased. For this reason, a crack is generated in the mounting portion of the conductor pin, and the conductor pin may fall due to a decrease in the mounting strength of the conductor pin.

  The present invention solves the problems shown in the background art, improves the adhesion between the substrate body made of glass-ceramic and the Cu metallized layer formed thereon, and the conductor pin brazed to the Cu metallized layer. It is an object of the present invention to provide a wiring board with increased attachment strength.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, the present invention provides a Cu-ceramic mixed layer between a glass-ceramic and a Cu metallized layer of a substrate body, and a brazing material having a high melting point for brazing a conductor pin to the Cu metallized layer. The idea is to apply an alloy.
That is, the wiring board of the present invention (Claim 1) comprises a substrate body made of glass-ceramic and having a front surface and a back surface, and formed on at least one of the front surface and the back surface of the substrate body, and Cu powder and ceramic powder. A Cu-ceramic mixed layer formed by mixing, a Cu metallized layer formed on the Cu-ceramic mixed layer, and a standing part above the Cu metallized layer via a brazing material having a melting point of 500 ° C. or more. And a conductor pin.

According to this, since the Cu-ceramic mixed layer is interposed between the glass-ceramic substrate body and the Cu metallized layer formed on at least one of the front surface and the back surface thereof, Adhesion can be reliably improved, and a difference in thermal expansion coefficient among the substrate body, the Cu metallized layer, and the brazing material can be suppressed. For this reason, it is possible to reliably prevent the conductivity between the internal wiring of the substrate body and the metallized layer from being lowered, or the metallized layer from being peeled off and the conductor pins being inadvertently detached.
Moreover, since the conductor pins are erected above the Cu metallization layer via a high melting point brazing material of 500 ° C. or higher, for example, at the time of reflow when mounting an electronic component such as an IC chip on the surface of the substrate body Further, it is possible to prevent the occurrence of cracks in the mounting portion of the conductor pin, and to reliably prevent the conductor pin from falling down.
Accordingly, the wiring board can be reliably connected to a printed board such as a mother board through the conductor pins, and the electronic component can be mounted reliably.

The glass-ceramic includes glass-alumina (Al ₂ O ₃ ), glass-silicic acid (SiO ₂ ), glass-aluminum nitride, glass-zirconium oxide, glass-mullite, and the like.
The Cu-ceramic mixed layer is made of, for example, a mixed material of Cu powder and alumina powder, and the volume ratio is, for example, about 5: 1.
Furthermore, for the brazing material having a melting point of 500 ° C. or higher, for example, a 72 wt% Ag-28 wt% Cu alloy having a melting point of about 780 ° C. is used.
In addition, so-called 42 alloy (Fe-42 wt% Ni), Kovar (Fe-29 wt% Ni-17 wt% Co), or the like is used for the conductor pin.

Further, in the present invention, a wiring layer made of glass with an opening edge covering the outer peripheral portion thereof is formed around the Cu-ceramic mixed layer and the Cu metallized layer. 2) is also included.
According to this, since the coating layer made of glass is formed so as to cover the outer peripheral portion of the Cu-ceramic mixed layer and the Cu metallized layer, these are physically strengthened closer to the glass-ceramic of the substrate body. It can be adhered. Therefore, it is possible to more reliably prevent a situation in which the conductivity between the internal wiring of the substrate body and the Cu metallized layer is reduced or the Cu metallized layer is peeled off and the conductor pin is inadvertently detached.

Further, the present invention, the glass - ceramic, glass - is alumina, the ceramic powder is alumina powder, the wiring substrate (claim 3) are also included.
In addition, after forming a Ni plating layer in advance on the surface of the Cu metallized layer, conductor pins may be brazed via the brazing material. Such a Ni plating layer makes it possible to improve the corrosion resistance of the Cu metallized layer and the wettability with the brazing material.
In addition, the Ni plating layer and the Au plating layer are formed on the surface of the conductor pin brazed above the Cu metallized layer and the surface of the brazing material near the nail head portion, thereby ensuring the corrosion resistance. It becomes possible to do.

In the following, the best mode for carrying out the present invention will be described.
FIG. 1 is a cross-sectional view showing an outline of a wiring board 1 of the present invention, and FIG. 2 is a partially enlarged view of a one-dot chain line portion A in FIG.
As shown in FIGS. 1 and 2, the substrate body 2 includes a substrate body 2 having a front surface 3 and a back surface 4, a plurality of Cu-ceramic mixed layers 20 formed on the back surface 4 of the substrate body 2, and each Cu A plurality of Cu metallized layers 22 formed on each ceramic mixed layer 20 and conductor pins 26 erected on each Cu metallized layer 22 via a brazing material 23 are included.
The substrate body 2 is formed by integrally laminating insulating layers 5 to 7 made of glass-alumina (ceramic). The Cu-ceramic mixed layer 20 is a mixture of Cu powder and alumina (ceramic) powder in a predetermined ratio. Further, the brazing material 23 is made of a 72 wt% Ag-28 wt% Cu alloy having a melting point of about 780 ° C. (500 ° C. or higher).

As shown in FIGS. 1 and 2, wiring layers 9 and 10 made of Cu are formed between the insulating layers 5 to 7 of the substrate body 2, and a plurality of connections made of Cu are formed on the surface 3 of the substrate body 2. The pads 14 are formed, and via conductors 11 to 13 made of Cu are connected between these pads and the Cu metallized layer 22 on the back surface 4.
On the back surface 4 of the substrate body 2, a coating layer 8 made of glass with an opening edge 19 of the through hole 18 covering the outer peripheral portion of the Cu-ceramic mixed layer 20 and the Cu metallized layer 22 is formed with a required thickness. Has been. The covering layer 8 is made of, for example, glass mainly containing silicic acid, and a plurality of through holes 18 are opened on the surface 8a.
For the coating layer 8 made of glass, a glass-alumina having the same component as that of the substrate body 2 and a color powder such as Cr, Mn, or Fe may be used.

As shown in FIG. 2, a conductor pin 26 made of, for example, 42 alloy is erected via a brazing material 23 above each Cu metallized layer 22 (downward in the drawing). The nail head portion 28 of the conductor pin 26 faces the Cu metallized layer 22 with a gap 24 interposed therebetween. The plurality of conductor pins 26 are used to connect the wiring board 1 itself to a relay board (not shown) or a surface electrode of a mother board.
The surfaces of the conductor pins 26 and the brazing material 23 are covered with a Ni plating layer and an Au plating layer (not shown) with a predetermined thickness. Further, the surface of the Cu metallized layer 22 may be covered with a Ni plating layer.

Incidentally, the size of the substrate body 2 is 51 mm × 51 mm × thickness 2 mm, the thickness of the coating layer 8 made of glass is about 20 μm, the diameter of the conductor pin 26 is 0.3 mm, and the diameter of the nail head portion 28 is 0. .65 mm.
As shown in FIG. 1, on the plurality of connection pads 14 located on the surface 3 of the substrate body 2, an alloy having a low melting point of about 230 ° C. (for example, 96.5 wt% Sn-3.5 wt% Sb) is used. The external chip 17 provided on the bottom surface of the IC chip (electronic component) 16 is connected via the brazing material 15 to be mounted on the IC chip 16.

  According to the wiring substrate 1, the Cu-ceramic mixed layer 20 is interposed between the glass-ceramic of the substrate body 2 and the Cu metallized layer 22 formed on the back surface 4. And the difference in thermal expansion coefficient among the substrate body 2, the Cu metallized layer 22, and the brazing material 23 can be suppressed. For this reason, the conduction between the wiring layers 9 and 10 and the metallized layer 22 can be surely taken via the via conductors 11 to 13, and it is possible to reliably prevent the metallized layer 22 from peeling off and the conductor pins 26 from being inadvertently detached. . Moreover, since the conductor pins 26 are erected above the Cu metallized layer 22 via a high melting point brazing material 23 having a melting point of 500 ° C. or higher, during reflow when the IC chip 30 is mounted on the surface 3 of the substrate body 2. Cracks are not generated in the covering layer 8 at the portion where the conductor pin 26 is attached, and the conductor pin 26 can be reliably prevented from falling. Furthermore, since the coating layer 8 made of glass is formed so as to cover the outer peripheral portions of the Cu-ceramic mixed layer 20 and the Cu metallized layer 22, they are physically strengthened on the glass-ceramic side of the substrate body 2. It is closely attached to. Therefore, electrical connection with a printed board such as a mother board can be ensured through the conductor pins 26, and the IC chip 16 can be mounted on the surface 3 with certainty.

Below, the manufacturing method of the said wiring board 1 is demonstrated.
A plurality of glass-ceramic green sheets are prepared in advance. Such a green sheet is made of a mixture of glass powder, ceramic powder as a filler, an organic binder, a plasticizer, an organic solvent, and the like.
Examples of the glass component of the glass powder include SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —MO system (where M is Ca, Sr, Mg, Ba or Zr), PB glass, Bi glass or the like.
Examples of the ceramic powder include composite oxides of Al ₂ O ₃ —SiO ₂ —ZrO ₂ and alkali rare earth metal oxides, composite oxides of TiO ₂ and alkali rare earth metal oxides, Al ₂ O ₃ and Examples include composite oxides containing at least one selected from SiO ₂ such as spinel and mullite cordierite.
The glass powder and ceramic powder are mixed at a weight ratio of 40:60 to 99: 1.

Furthermore, the organic binder blended in the green sheet includes, for example, acrylic, polyvinyl butyral, polyvinyl alcohol, acrylic-styrene, polypropylene carbonate, or cellulose homopolymers or copolymers.
In addition to the glass powder, the ceramic powder, and the organic binder, the green sheet further includes a necessary amount of plasticizer and solvent (organic solvent or water) to form a slurry, and the slurry is subjected to a doctor blade method, rolling It can be obtained by molding into a sheet having a thickness of several tens to several hundreds of micrometers by a method, a calender roll method, a die press method, or the like.

Then, a conductive paste containing Cu powder is printed and formed in a predetermined pattern on at least one of the front and back surfaces of the obtained plurality of glass-ceramic green sheets by screen printing or the like, and the green sheet The conductive paste is also filled in the via hole penetrating through.
As a result, as illustrated in FIG. 3, a green sheet s 7 having the insulating layer 7 later and having the internal wiring layer 10 and the via conductor 13 is obtained.
Next, as shown in FIG. 4 in which the one-dot chain line portion B in FIG. 3 is enlarged, from a mixed material in which Cu powder and alumina powder are blended at a volume ratio of 5: 1 at a predetermined position on the back surface 4 of the green sheet s7. And a Cu-ceramic mixed layer 20 having a thickness of about 20 μm is formed by screen printing or the like.

Further, as shown in FIG. 5, a Cu metallized layer 22 having a thickness of about 15 μm is formed on the surface (upper) of each Cu-ceramic mixed layer 20 by screen printing. Since the Cu metallized layer 22 is formed on the back surface 4 of the green sheet s7 including the end surface of the via conductor 13 via the Cu-ceramic mixed layer 20, the Cu metallized layer 22 is stronger than the case where it is directly formed on the back surface 4. Be joined.
Subsequently, after applying a predetermined masking (not shown) so as to surround the outer periphery of the Cu-ceramic mixed layer 20 and the Cu metallized layer 22, as shown in FIG. The soft glass coating layer 8 made of the glass component is formed by coating or the like. When the coating layer 8 is solidified, as shown in FIG. 6, the opening edge 19 of the through-hole 18 opening on the surface 8 a of the coating layer 8 made of glass covers the outer peripheral portion of the Cu-ceramic mixed layer 20 and the Cu metallized layer 22. It becomes a covering shape.

In this state, the green sheet s7 including the coating layer 8 and the green sheet to be the insulating layers 5 and 6 are stacked, and the obtained stacked body is heated to a temperature range of, for example, 100 to 800 ° C. Organic components such as a binder are removed, and further heated to a temperature range of about 800 to 1000 ° C. and fired.
As a result, as shown in FIG. 7, the substrate body 2 is composed of glass-ceramic insulating layers 5 to 7, and has internal wiring layers 9 and 10, via conductors 11 to 13, and connection pads 14 on the surface 3, The coating layer 8 formed on the back surface 4 is obtained.
Next, as shown in FIG. 8 in which the one-dot chain line portion C in FIG. 7 is enlarged, the surface of the Cu metallized layer 22 is covered with a Ni plating layer 21 having a thickness of 2 to 5 μm.

Further, as indicated by an arrow in FIG. 8, in the coating layer 8 made of glass, for example 42 in the surface of the Cu metallized layer 22 exposed on the bottom surface or in the through hole 18 where the Ni plating layer 21 is exposed on the bottom surface. The conductor pin 26 made of alloy is inserted so that the nail head portion 28 is opposed. A brazing material 25 made of a 72 wt% Ag-28 wt% Cu alloy having a melting point of about 780 ° C. (500 ° C. or higher) is formed in a substantially hemispherical shape on the upper surface of the nail head portion 28 in advance.
With the brazing material 25 in contact with the Cu metallized layer 22 or the Ni plating layer 21 and with the axis of the conductor pin 26 kept at a right angle to the back surface 4 of the substrate body 2, the brazing material 25 is melted at its melting point. Heat (sinter) near the temperature just above.

As a result, as shown in FIG. 9, when the brazing material 25 is melted, it has a substantially conical shape solidified so as to surround the nail head portion 28 of the conductor pin 26 including the gap 24 with the plated layer 21. The brazing material 23 is obtained. For this reason, the conductor pin 26 can be erected above the back surface 4 of the substrate body 2 through the brazing material 23.
Then, Ni plating and Au plating are applied to the surfaces of the conductor pins 26 and the brazing material 23. As a result, as illustrated in the enlarged partial surface in FIG. 9, a portion of the dotted line C in FIG. Layer 29b is coated. The Au plating layer 29b ensures the corrosion resistance of the conductor pin 26 and the brazing material 23.
The wiring substrate 1 shown in FIG. 1 is obtained through the above steps.

Further, in order to mount the IC chip 16 above the surface 3 of the substrate body 2, the IC chip is disposed on the plurality of connection pads 14 located on the surface 3 via the brazing material 15 made of the Sn—Sb alloy having a low melting point. In the state where the external electrode 17 provided on the bottom surface of 16 is placed, the brazing material 15 is heated (reflowed) near its melting point. Even during such reflow, since it is in a temperature range of about 230 ° C., the high melting point Ag—Cu alloy brazing material 23 brazing the conductor pin 26 on the back surface 4 side of the substrate body 2 is softened. do not do. For this reason, in the wiring board 1, it becomes possible to prevent pin collapse reliably.
The step of coating the Ni plating layer 21 on the surface of the Cu metallized layer 22 can be omitted.

The present invention is not limited to the form described above.
For example, the volume ratio of Cu and ceramic in the Cu-ceramic mixed layer 20 can be appropriately selected within a range of 10: 1 to 2: 1.
It is also possible to form the Cu-ceramic mixed layer 20 or the Cu metallized layer 22 only on the surface 3 of the substrate body 2 and to erect the conductor pins 26 on the surface 3 side through the brazing material 23. Alternatively, the conductor pins 26 can be erected on both the front surface 3 and the back surface 4 of the substrate body 2.
Further, the substrate main body 2 may be configured to have a cavity opened on the surface 3, and in such a configuration, electronic components such as the IC chip 16 are mounted in the cavity.
The brazing material 25 may be made of an Ag—Cu alloy or other alloy other than the above composition as long as the melting point is 500 ° C. or higher.
In addition, the material of the conductor pin 26 is not limited to 42 alloy, and may be Kovar or a Cu-based alloy (for example, Cu-2.3 wt% Fe-0.03 wt% P).

Sectional drawing which shows the outline of the wiring board of this invention. The elements on larger scale of the dashed-dotted line part A in FIG. Schematic which shows the manufacturing process for obtaining the said wiring board. FIG. 4 is a partially enlarged view of a one-dot chain line portion B in the manufacturing process subsequent to FIG. 3. Schematic which shows the manufacturing process following FIG. Schematic which shows the manufacturing process following FIG. Schematic which shows the manufacturing process following FIG. Schematic which shows the manufacturing process following FIG. Schematic which shows the manufacturing process following FIG. 8, and the one part enlarged view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wiring board 2 ... Board | substrate body 3 ... Front surface 4 ... Back surface 8 ... Coating layer which consists of glass 20 ... Cu-ceramics mixed layer 22 ... Cu metallization layer 23 ... Brazing material 26 ... Conductor pin

Claims (3)

A substrate body made of glass-ceramic and having a front surface and a back surface;
A Cu-ceramic mixed layer formed on at least one of the front surface and the back surface of the substrate body and formed by mixing Cu powder and ceramic powder;
A Cu metallization layer formed on the Cu-ceramic mixed layer;
A conductor pin standing above the Cu metallization layer via a brazing material having a melting point of 500 ° C. or higher,
A wiring board characterized by that. Around the Cu-ceramic mixed layer and the Cu metallized layer, a coating layer made of glass with an opening edge covering these outer peripheral portions is formed.
The wiring board according to claim 1. The glass-ceramic is glass-alumina, and the ceramic powder is alumina powder .
The wiring board according to claim 1 or 2, wherein

Images