JP2005243733A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board with low electric resistance that is superior in connection reliability by preventing a metallized wiring layer from peeling off from an insulating substrate effectively, when the metallize wiring layer formed of copper or alloy made mainly of copper is electrically connected with an external electric circuit by means of a low-melting-point soldering material. <P>SOLUTION: The wiring board 9 is provided with an insulating substrate 1 formed of a glass ceramic sintered body and a metallized wiring layer 2 that is formed on the surface of the insulating substrate 1 and is formed of copper or alloy made mainly of copper, and the metallized wiring layer 2 is electrically connected with an external electric circuit by means of a low-melting-point soldering material. The metallized wiring layer 2 includes 0.5-10 parts by weight of forsterite to 100 parts by weight of copper in the region connected with the external electric circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, a metallized wiring layer of copper or a copper-based alloy is formed on the surface of an insulating base made of a glass ceramic sintered body, and this metallized wiring layer is connected to an external electric circuit via a low melting point brazing material. The present invention relates to a printed wiring board.

  Semiconductor integrated circuit elements such as IC and LSI, LD (semiconductor laser), LED (light emitting diode), PD (photodiode), CCD, line sensor, optical semiconductor element such as image sensor, piezoelectric vibrator, crystal vibrator, etc. As a wiring board on which a vibrator and other various electronic components are mounted, an insulating substrate made of a glass ceramic sintered body and a metallized wiring layer made of copper or an alloy containing copper as a main component and formed on the surface of the insulating substrate The thing of the structure which comprises is known.

  In such a wiring board, since the metallized wiring layer is made of copper having a low electrical resistance or an alloy containing copper as a main component, the metallized wiring layer can have a low electrical resistance, and an electronic component to be mounted can be externally connected. It can be electrically connected to the electric circuit with low resistance.

  An electronic component is mounted on the upper surface of the insulating base, and the electrodes of the electronic component are electrically connected to the metallized wiring layer via bonding wires, metal bumps, or the like to form an electronic device. Further, a part of the metallized wiring layer that is not connected to the electrode of the electronic component is electrically and mechanically connected to the external electric circuit via a low melting point brazing material such as tin-lead solder.

Such a wiring board is manufactured as follows, for example. First, a raw material powder in which a suitable glass powder is mixed with a ceramic powder is formed into a sheet shape together with an organic solvent and a binder to produce a ceramic green sheet (green sheet), and then copper or a copper-based metal A metal paste is prepared by adding an organic solvent and a binder to the powder and kneading the metal paste onto a green sheet by a screen printing method to a predetermined metallized wiring layer pattern. Accordingly, a plurality of layers are stacked one above the other and then fired at a temperature of about 1000 ° C. During firing, the glass component of the green sheet melts and enters between the copper powder of the metal paste, and the metal paste is sintered integrally with the green sheet through this glass component (liquid phase sintering). The metallized wiring layer is bonded to the surface of the insulating substrate.
JP 2003-212646 A JP 2003-201170 A

  However, when a metallized wiring layer of copper or an alloy containing copper as a main component is formed on the surface of an insulating base made of a glass ceramic sintered body, the melting point of copper is relatively low (about 1083 ° C.). Since the components are easily melted, it is difficult to sinter the glass components sufficiently between the copper powders, and the bonding strength of the metallized wiring layer to the insulating substrate tends to be low.

In addition, the coefficient of thermal expansion (about 12 to 16 × 10 ⁻⁶ / ° C.) of an external electric circuit board (printed wiring board or the like) having an external electric circuit formed on the surface and the coefficient of thermal expansion (6 to 12) of the insulating substrate. A large thermal stress is generated due to the difference from about 10 × ^{6 −6} / ° C., and this thermal stress acts on the low melting point brazing material and the connection pad.

  Therefore, when the metallized wiring layer is connected to an external electric circuit via a low melting point brazing material, there is a problem that the metallized wiring layer is peeled off from the insulating substrate due to the stress such as the thermal stress.

  In particular, as a low melting point brazing filler metal, a so-called lead-free solder such as a tin-silver type has come to be used instead of a tin-lead solder generally used conventionally. -Compared with lead solder, the soldering temperature of lead-free solder is higher, so the thermal stress when electrically connecting the metallized wiring layer to an external electric circuit also becomes larger, causing problems such as peeling of the metallized wiring layer. It tends to be easier.

  The present invention has been devised in view of the above-described conventional problems, and an object thereof is to electrically connect a metallized wiring layer made of copper or a copper-based alloy to an external electric circuit via a low melting point brazing material. An object of the present invention is to provide a wiring board having excellent connection reliability and low electrical resistance, which effectively prevents the problem that the metallized wiring layer is peeled off from the insulating substrate when connected electrically.

  The wiring board of the present invention comprises an insulating base made of a glass ceramic sintered body, and a metallized wiring layer of copper or an alloy containing copper as a main component formed on the surface of the insulating base. In the wiring board in which the wiring layer is electrically connected to the external electric circuit through the low melting point brazing material, the metallized wiring layer is formed of forsterite with respect to 100 parts by mass of copper at the portion connected to the external electric circuit. It contains 0.5 to 10 parts by mass.

The wiring board of the present invention is preferably characterized in that the glass ceramic sintered body has a thermal expansion coefficient of 11 × 10 ^{−6 to} 13 × 10 ⁻⁶ / ° C.

  The wiring board of the present invention is preferably characterized in that the glass-ceramic sintered body contains 15 to 20% by mass of barium oxide and 2 to 7% by mass of boron oxide.

  According to the wiring board of the present invention, the metallized wiring layer contains 0.5 to 10 parts by mass of forsterite with respect to 100 parts by mass of copper in the portion connected to the external electric circuit, so that the wetness with respect to the glassy material is achieved. The forsterite material with good properties is entangled with the vitreous material of the sintered glass ceramic, and the metallized wiring layer is firmly bonded to the insulating substrate by the anchor effect of this forsterite, so it consists of copper or an alloy containing copper as a main component. Even when the metallized wiring layer is electrically connected to an external electric circuit via a low melting point brazing filler metal, it is possible to effectively prevent the problem that the metallized wiring layer is peeled off from the insulating substrate, and the connection reliability can be effectively prevented. In addition, it is possible to provide a wiring board having excellent electrical properties and low electrical resistance.

In the wiring board of the present invention, preferably, the glass ceramic sintered body has a thermal expansion coefficient of 11 × 10 ^{−6 to} 13 × 10 ⁻⁶ / ° C. It is possible to provide a wiring board that is close to the thermal expansion coefficient of the board and that is further excellent in connection reliability.

In the wiring board of the present invention, preferably, the glass ceramic sintered body contains 15 to 20% by mass of barium oxide and 2 to 7% by mass of boron oxide. A glass ceramic sintered body of ^{−6 to} 13 × 10 ⁻⁶ / ° C. can be produced more easily and reliably.

  Next, the wiring board of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a sectional view showing an example of an embodiment of a wiring board according to the present invention.

  In these drawings, 1 is an insulating substrate and 2 is a metallized wiring layer. The insulating substrate 1 and the metallized wiring layer 2 mainly constitute a wiring board 9.

  The insulating substrate 1 is formed of a glass ceramic sintered body such as silica or alumina.

  If the insulating substrate 1 is made of, for example, a silica-based glass ceramic sintered body, a raw material powder made of glass powder such as barium oxide and ceramic powder such as silica is formed into a sheet shape together with an organic solvent and a binder. It is manufactured by obtaining a sheet of green sheets, subjecting them to appropriate drilling, laminating them up and down, and firing them at about 1000 ° C.

  The insulating substrate 1 is a semiconductor integrated circuit element such as an IC or LSI, an LD (semiconductor laser), an LED (light emitting diode), a PD (photodiode), a CCD, a line sensor, an optical semiconductor element such as an image sensor, a piezoelectric vibrator, It functions as a base for mounting and supporting a vibrator such as a crystal vibrator and other various electronic components, and the electronic components are mounted on the main surface (the upper surface in this example) and side surfaces.

  A metallized wiring layer 2 is formed on the surface of the insulating substrate 1.

  The metallized wiring layer 2 is formed, for example, from the main surface on which the electronic component of the insulating base 1 is mounted to another main surface or side surface, and is an electrode of an electronic component (not shown) mounted on the wiring substrate 9. Is led out and electrically connected to an external electric circuit (not shown). The metallized wiring layer 2 may also be formed inside the insulating substrate 1.

  The metallized wiring layer 2 is formed of copper or an alloy containing copper as a main component. As an alloy mainly composed of copper, an alloy such as copper and tungsten or copper and molybdenum is used.

  The metallized wiring layer 2 is formed, for example, by printing and applying a metal paste of copper or an alloy (mixture) containing copper as a main component on the surface of the green sheet.

  The metallized wiring layer 2 is preferably covered with the plating layer 3 on the surface.

  If the surface of the metallized wiring layer 2 is covered with the plating layer 3, the metallized wiring layer 2 is more effectively prevented from being oxidized by contact with the outside air, and the bonding property of the bonding wire and the low melting point brazing material It is possible to improve the wettability and the like.

  As such a plating layer 3, a nickel alloy such as nickel or nickel-cobalt, a plating layer such as gold, copper, palladium, or platinum can be deposited.

  In this case, since the plating layer 3 is an anti-oxidation protective layer, it is preferable that the gold plating layer is located at least on the outermost surface. In particular, the bonding strength between the metallized wiring layer 2 and the plating layer 3 can be ensured. In order to reliably coat the metallized wiring layer 2 with the plating layer 3 and prevent oxidation more effectively, the metallized wiring layer 2 is composed of a nickel or copper plating layer and a gold plating layer sequentially deposited from the surface of the metallized wiring layer 2. More preferably.

  For example, in the case of a gold plating layer, the plating layer 3 contains the insulating substrate 1 to which the metallized wiring layer 2 is deposited, a cyan gold compound as a gold source, a pH adjuster, a complexing agent, and the like. Is formed on the surface of the metallized wiring layer 2 by applying a predetermined current to the exposed surface of the metallized wiring layer 2 through a plating jig or the like. Is done. In addition, as a pretreatment for plating, the metallized wiring layer 2 is subjected to an alkaline degreasing treatment or an acid treatment with an acid (such as dilute hydrochloric acid).

  The electronic component is mounted on the upper surface of the insulating base 1 and the electrode of the electronic component is electrically connected to a predetermined portion of the metallized wiring layer 2 through a conductive connecting material such as a bonding wire or solder, and metallized. A part of the wiring layer 2 that is not connected to the electrode of the electronic component is electrically and mechanically connected to an external electric circuit via a low-melting point brazing material (not shown), thereby the metallized wiring layer 2. The electronic component is electrically connected to the external electric circuit via the.

  Low melting point brazing materials include tin-lead (eutectic) solder, tin-silver, tin-silver-copper, tin-silver-copper-bismuth, tin-silver-copper-zinc solder, etc. Is used.

  According to the wiring board 9 of the present invention, the metallized wiring layer 2 contains 0.5 to 10 parts by mass of forsterite with respect to 100 parts by mass of copper in the portion connected to the external electric circuit. Forsterite, which has good wettability against glass, is entangled with the vitreous material of the sintered glass ceramic, and the metallized wiring layer 2 is firmly bonded to the insulating substrate 1 by the anchor effect of this forsterite. Even when the metallized wiring layer 2 made of an alloy is electrically connected to an external electric circuit via a low melting point brazing material, it is possible to effectively prevent the metallized wiring layer 2 from being peeled off from the insulating substrate 1. Therefore, it is possible to provide the wiring board 9 having excellent connection reliability and low electrical resistance.

  In this case, if the forsterite is less than 0.5 parts by mass with respect to 100 parts by mass of copper in the portion connected to the external electric circuit, the metallized wiring layer 2 is sintered with only copper at the time of sintering and insulated from copper. Adhesive strength with the substrate 1 (green sheet) cannot be sufficiently obtained, so that the bonding of the metallized wiring layer 2 to the insulating substrate 1 cannot be made sufficiently strong. A large amount of glass is present on the surface of the sintered body of the layer 2 and copper is not sufficiently sintered. On the contrary, the bonding of the metallized wiring layer 2 to the insulating substrate 1 is weakened. Further, when the conductive resistance of the metallized wiring layer 2 is increased or the plating layer 3 is deposited, the deposition strength of the plating layer 3 is deteriorated.

  In order to include 0.5 to 10 parts by mass of forsterite with respect to 100 parts by mass of copper in the part connected to the external electric circuit for the metallized wiring layer 2, in the metal paste that becomes the metallized wiring layer 2, Means such as adding forsterite to 0.5 to 10 parts by mass with respect to 100 parts by mass of the metal powder can be used.

  Similarly, the metallized wiring layer 2 may contain 0.5 to 10 parts by mass of forsterite in parts other than the part connected to the external electric circuit.

  For example, when printing a metal paste that becomes the metallized wiring layer 2 on a green sheet, it is possible to print the same green paste on the same green sheet at the same time with one printing plate making for productivity and firing. It is preferable in terms of control and control of the shrinkage rate. Therefore, it is preferable that the layer of the metallized wiring layer 2 including the portion connected to the external electric circuit includes 0.5 to 10 parts by mass of forsterite throughout the entire area.

Moreover, in the wiring board 9 of the present invention, the glass ceramic sintered body preferably has a thermal expansion coefficient of 11 × 10 ^{−6 to} 13 × 10 ⁻⁶ / ° C.

When the thermal expansion coefficient of the glass-ceramic sintered body is set to 11 × 10 ^{−6 to} 13 × 10 ⁻⁶ / ° C., the thermal expansion coefficient of the insulating substrate 1 can be brought close to the thermal expansion coefficient of the external electric circuit board. Therefore, it is possible to provide the wiring board 9 having further excellent connection reliability.

  For the glass-ceramic sintered body having such a thermal expansion coefficient, for example, a method of increasing the addition amount of a silica-based component (quartz, cristobalite, tridymite, etc.) having a large thermal expansion coefficient can be used.

  Moreover, as for the wiring board 9 of this invention, it is preferable that the glass ceramic sintered compact contains 15-20 mass% of barium oxides, and 2-7 mass% of boron oxides.

When the glass ceramic sintered body contains 15 to 20% by mass of barium oxide and 2 to 7% by mass of boron oxide, the thermal expansion coefficient is 11 × 10 ^{−6 to} 13 × 10 ⁻⁶ / ° C. The wiring board 9 can be easily and reliably controlled and obtained, and the connection reliability is further improved.

  Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the plating layer 3 that covers the metallized wiring layer 2 may be configured differently in a portion that becomes the connection pad 3 and another portion.

  A flat insulating substrate 1 having an outer dimension of 1 cm × 1 cm was formed of a glass ceramic sintered body having a silica-based composition, and a metallized wiring layer 2 was formed on the surface thereof with copper to obtain a test wiring substrate 9.

  Of the metallized wiring layer 2, the one exposed on one main surface of the insulating base 1 is a linear pattern having a width of 0.5 mm, and the one exposed on the opposite main surface is a circular shape having a diameter of 0.5 mm. The patterns were arranged in a 10 × 10 array vertically and horizontally.

  On the exposed surface of the metallized wiring layer 2, a nickel plating layer having a thickness of 2 to 5 μm and a gold plating layer having a thickness of 1.5 to 2 μm were sequentially deposited by electrolytic plating.

  Then, the circular pattern was connected to the electric circuit of the printed wiring board 9 through tin-lead (eutectic) solder, and the bonding strength was measured.

  The strength of the wiring conductor was tested by changing the amount of forsterite added to copper as shown in Table 1.

The results are shown in Table 1.

  As can be seen from Table 1, forsterite is added in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of copper, and within the scope of the present invention, bonding between the metallized wiring layer 2 and the insulating substrate 1 is performed. Was sufficiently strong and had good connection reliability.

  On the other hand, when the amount of forsterite added is less than 0.5 parts by mass with respect to 100 parts by mass of copper, sufficient adhesion strength between copper and the insulating substrate 1 cannot be obtained, and the bonding strength of the metallized wiring layer 2 is obtained. Insufficient malfunction occurred. In addition, when the amount exceeds 10 parts by mass, an increase in conduction resistance and a problem that the deposition strength of the plating layer 3 deteriorates when the plating layer 3 is deposited are observed.

It is sectional drawing which shows an example of embodiment of the wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulation base | substrate 2 ... Metallized wiring layer 3 ... Plating layer 9 ... Wiring board

Claims (3)

An insulating substrate made of a glass ceramic sintered body, and a metallized wiring layer of copper or an alloy containing copper as a main component formed on the surface of the insulating substrate, the metallized wiring layer being a low melting point brazing material In the wiring board electrically connected to the external electric circuit via the metallized wiring layer, the metallized wiring layer is 0.5 to 10 parts by mass of forsterite with respect to 100 parts by mass of copper in the part connected to the external electric circuit. A wiring board comprising the wiring board. The wiring substrate according to claim 1, wherein the glass ceramic sintered body has a thermal expansion coefficient of 11 × 10 ^{−6 to} 13 × 10 ⁻⁶ / ° C. The wiring substrate according to claim 1 or 2, wherein the glass ceramic sintered body contains 15 to 20% by mass of barium oxide and 2 to 7% by mass of boron oxide.

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