JP6738690B2 - Ceramic wiring board manufacturing method - Google Patents

Description

The present invention relates to a method of manufacturing a ceramic wiring board that can efficiently perform signal transmission in a high frequency band, for example.

Conventionally, low resistance Au, Ag, and Cu are used for the conductor of the ceramics wiring board capable of efficiently transmitting a signal in a high frequency band according to the purpose.
Here, Ag may cause migration and electrical failure (such as a short circuit) when an electric field is applied in a high humidity state. Considering high reliability, Ag is suitable for use. Has room for consideration.

Further, from the viewpoint of applicability, with respect to Cu, when a resistor that can be fired in the air is provided, for example, in a firing atmosphere, characteristic loss occurs due to oxidation, and therefore there is room for consideration for its use.

Therefore, it is considered that the use of the Au conductor is suitable for the requirements of high reliability and applicability (for example, firing in the atmosphere). The Au conductor is formed by Au metallization made of Au or containing Au as a main component, for example.

Further, there is a solder mounting method as an example of the assembly process of the ceramic wiring board. When the conventional solder mounting method is used for the ceramic wiring board using Au metallization, the Au metallization is alloyed and absorbed by the solder. (So-called solder metallization of Au metallization) may occur, and the Au conductor pattern may disappear.

As a countermeasure against this, as shown in FIG. 6, a first coating (P3) made of Ni or a Ni-based alloy is provided on the surface of the Au metallization (P2) on the ceramic substrate (P1), and the first coating (P3) is provided. There is known a technique of providing a second coating (P4) made of Au or an Au-based alloy on the surface of the.

Note that there are cases where components such as Bi are contained in the Au metallization depending on the application.
Further, Patent Document 1 below discloses a technique related to the above-described technique, in which a Ni-based alloy coating film is formed on Au metallization by electroless plating.

JP-A-8-306816

However, when the Ni-based alloy coating film is formed on the Au metallization by electroless plating according to the above-described conventional technique, components such as Bi function as catalyst poisons during Ni plating. It is not easy to form a Ni-based alloy coating on the substrate.

Another method of manufacturing a ceramic wiring board, which is different from this, is a method of plating the surface of a metal layer formed by a sputtering method. However, Ti, which is generally used as a metal layer formed by sputtering, is a magnetic material and may cause a problem of large eddy current loss in a high frequency band, and is not always preferable.

The present invention has been made in view of such a background, and provides a method for manufacturing a ceramics wiring board capable of suitably forming a coating film of Ni or a Ni-based alloy on the surface of a conductor layer made of Au metallization.

(1) According to a first aspect of the present invention, in the method for manufacturing a ceramic wiring substrate in which wiring is formed on a ceramic substrate, at least one of Bi, Pb, Cu, Sn, Zn, and W is used as the step of forming the wiring. Conductor layer forming step of forming a conductor layer containing one kind or a compound thereof and having Au as a main component on the ceramic substrate, and Ni or Ni alloy by electrolytic plating so as to cover the surface of the conductor layer. A first surface layer forming step of forming a first surface layer made of, and a second surface layer forming step of forming a second surface layer made of Au or Au alloy so as to cover the surface of the first surface layer. Have.

In the first aspect, in the conductor layer forming step, a conductor layer containing at least one of Bi, Pb, Cu, Sn, Zn, and W or a compound thereof and containing Au as a main component (that is, Au metallization). ) Is formed on the ceramic substrate.

In addition, in the first surface layer forming step, a first surface layer (for example, a coating) made of Ni or a Ni alloy is formed by electrolytic plating so as to cover the surface of the conductor layer.
Further, in the second surface layer forming step, a second surface layer made of Au or an Au alloy is formed so as to cover the surface of the first surface layer.

That is, when the first surface layer is formed by electroless plating as in the prior art, Bi, Pb, Cu, Sn, Zn, W and the compounds contained in the conductor layer and their compounds are catalyst poisons for electroless Ni plating. Therefore, it is not easy to form the first surface layer. On the other hand, in the present first aspect, since the first surface layer is formed by electrolytic plating, even when the conductor layer contains Bi, Pb, Cu, Sn, Zn, W or a compound thereof, the first surface layer is preferably formed. One surface layer can be formed.

Further, even if Bi, Pb, Cu, Sn, Zn, W or a compound thereof is added to the conductor layer, it is unlikely to adversely affect the formation of the first surface layer. It can be effective. For example, by adding Bi, the bondability between the conductor layer and the ceramic substrate can be improved.

Furthermore, in the first aspect, the metal layer made of Ti is not formed by the sputtering method, but the first surface layer is formed by electrolytic plating on the conductor layer containing Au as a main component. There is an advantage that a problem (that is, a problem of large eddy current loss in a high frequency band) is unlikely to occur.

In addition, when Au is used as a main component, a case of Au alone is also included.
(2) In the second aspect of the present invention, in the step of forming the second surface layer, the second surface layer is formed by any one method of electrolytic plating, electroless plating, sputtering, vapor deposition, and thermal spraying.

The second aspect exemplifies a preferred method of forming the second surface layer.
(3) According to a third aspect of the present invention, between the conductor layer forming step and the first surface layer forming step, the first main surface side surface of the ceramic substrate on which the conductor layer is formed and the first surface are formed. A base metal layer forming step of forming a conductive base metal layer so as to cover the main surface and a surface of the second main surface opposite to the main surface; and the base of the first main surface and the second main surface. A resist forming step of forming a plating resist so as to cover the surface of the metal layer, a resist removing step of removing the plating resist on the first main surface side, and an etching of the underlying metal layer on the first main surface side And an etching step of removing by.

The third aspect exemplifies a suitable treatment performed between the conductor layer forming step and the first surface layer forming step.
Thereby, the first surface layer can be preferably formed after forming the conductor layer.

Note that the following configurations can be adopted in the present invention.
The ceramics substrate is a substrate whose main component is ceramics, and the conductor layer is a conductive layer whose main component is Au. Here, the main component means that the component is contained in the largest amount in mass %.

The wiring, the conductor layer, the first surface layer, and the second surface layer have conductivity.
When the surface of the conductor layer is covered with the first surface layer, the entire surface is covered with the first surface layer so that the surface is not exposed. When the surface of the first surface layer is covered with the second surface layer, the entire surface is covered with the second surface layer so that the surface is not exposed.

As a material for forming the ceramic substrate, for example, various ceramics such as alumina and various glass ceramics can be adopted.
As the compound of Bi, Pb, Cu, Sn, Zn and W, for example, various oxides (for example, bismuth oxide, zinc oxide, etc.) can be adopted.

As the Ni alloy of the first surface layer, for example, Ni-Co, Fe-Ni, Fe-Cr-Ni, or the like can be adopted. Examples of the Au alloy of the second surface layer include Au-Cu, Au-Ag, Au-Co, Au-Ni, Au-Cu-Ag, Au-Cu-Cd, Au-Cu-Cd-Ag, and the like. Can be adopted.

The plating resist has a masking structure (so-called resist mask) that prevents a coating film from being formed by plating. As the plating resist, for example, a photosensitive resin or the like can be adopted.

As the base metal layer, for example, Ti, Cu, Mo, W, Mo-Mn, or the like can be adopted.

It is sectional drawing which shows the cross section which fractured|ruptured the ceramics wiring board of embodiment in the thickness direction. It is explanatory drawing which fractures|ruptures a ceramic wiring board in the thickness direction, and shows a part of manufacturing method of the ceramic wiring board of embodiment. It is explanatory drawing which fractures|ruptures a ceramic wiring board in the thickness direction, and shows a part of manufacturing method of the ceramic wiring board of embodiment. FIG. 3 is an explanatory view schematically showing a method of forming a resist mask in the method for manufacturing a ceramic wiring board of the embodiment. It is an explanatory view showing electrolytic plating in a manufacturing method of a ceramics wiring board of an embodiment. It is explanatory drawing of a prior art.

[1. Embodiment]
[1-1. Constitution]
First, the structure of the ceramic wiring board in the present embodiment will be described.

As shown in FIG. 1, the ceramic wiring substrate 1 includes a ceramic substrate 3 which is a substrate body made of glass ceramics and wiring 5 such as an electrode pad. The composition of the glass ceramics is, for example, a mass ratio of the glass component and the ceramic component of 1:1. Further, as the ceramic substrate 3, for example, an alumina sintered body containing 96% by mass of alumina may be adopted.

The ceramic substrate 3 is formed in a plate shape and has a first main surface 7 that is a front surface and a second main surface 9 that is a back surface. Here, the first main surface 7 of the ceramic substrate 3 is a surface (upper surface in FIG. 1) on one side in the thickness direction of the ceramic substrate 3, and the second main surface 9 is the ceramic substrate 3. Is the surface on the other side in the thickness direction.

The thickness of the ceramic substrate 3 is, for example, 1 mm. Wirings 5 are provided on the first main surface 7 of the ceramic substrate 3.
Although not shown, conductive ceramic vias and internal wiring layers are provided inside the ceramics substrate 3, and the wiring 5 is electrically connected to the vias and internal wiring layers. In order to perform the electroplating described later, the Au metallized layer 11 is electrically connected to a conductive conductor layer on the second main surface 9 via a via and an internal wiring layer, though not shown. There is.

The wiring 5 has an Au metallized layer 11 which is a conductor layer, a Ni—Co plated layer 13 which is a first surface layer, and an Au plated layer 15 which is a second surface layer. Hereinafter, each of the layers 11 to 15 will be described.

The Au metallized layer 11 is provided on the first main surface 7 of the ceramic substrate 3. The Au metallized layer 11 is a metallized layer containing gold (Au) as a main component, and contains, for example, bismuth (Bi) in addition to Au. Specifically, the Au metallized layer 11 is an alloy layer having a mass ratio of Au:Bi=85:1. Note that Bi is added to improve the bondability with the ceramic substrate 3.

The Au metallized layer 11 is formed by co-firing with the ceramic substrate 3. The Au metallized layer 11 has a thickness of, for example, 5 to 20 μm.
Although the Au metallized layer 11 contains Bi in this example, it is not Bi but, for example, a compound of Bi, or lead (Pb), copper (Cu), tin (Sn), zinc (Zn), or tungsten. It may include at least one of (W) or a compound thereof.

On the surface of the Au metallized layer 11, a Ni—Co plated layer 13 is provided by electrolytic plating described later. The Ni—Co plated layer 13 is provided so as to cover the entire surface of the Au metallized layer 11, and its thickness is, for example, 0.5 to 6 μm. As the mass ratio of Ni and Co, a Co content of less than 40 mass% (including Co) can be adopted.

Further, instead of the Ni—Co plated layer 13, a plated layer made of Ni or another Ni alloy can be adopted. As the Ni alloy, an alloy such as Fe-Ni or Fe-Cr-Ni can be adopted.

An Au plating layer 15 is provided on the surface of the Ni—Co plating layer 13 by electrolytic plating described later. The Au plating layer 15 is provided so as to cover the entire surface of the Ni—Co plating layer 13, and its thickness is, for example, 0.05 to 5.0 μm.

Further, instead of the Au plating layer 15, a plating layer made of Au alloy can be adopted. As the Au alloy, alloys such as Au-Cu, Au-Ag, Au-Co, Au-Ni, Au-Cu-Ag, Au-Cu-Cd, Au-Cu-Cd-Ag can be adopted. As a method of forming the Au plated layer 15, well-known methods such as electroless plating can be adopted in addition to electrolytic plating.

It should be noted that electronic parts such as semiconductor chips, metal fittings, another substrate, etc. (not shown) are mounted on the above-described ceramic wiring board 1 by a solder mounting method, a wire bonding method, or the like.
[1-2. Production method]
Next, a method of manufacturing the ceramic wiring board 1 will be described.

<Conductor layer forming step>
First, as shown in FIG. 2A, the ceramic substrate 3 and the Au metallized layer 11 are formed by simultaneous firing.

Specifically, a ceramic green sheet made of a mixture of glass and alumina is manufactured by a known method (for example, doctor blade method).
A metal paste made of Au is applied to the surface of the ceramic green sheet by screen printing or the like. A metal via conductor (not shown) made of Au is also formed on the ceramic green sheet.

And the laminated body which laminated|stacked these ceramic green sheets is produced.
Then, the laminated body (that is, a plurality of ceramic green sheets), the metal paste, and the via conductor are simultaneously fired at a firing temperature of 900 to 1400°C.

Thereby, the ceramic substrate 3 and the Au metallized layer 11 are formed. That is, the Au metallized layer 11, which is a conductor layer, is formed on the first main surface 7 of the ceramic substrate 3.
Note that the Au metallized layer 11 and the conductor layer on the second main surface 9 are electrically connected via a via (that is, a via obtained by firing the via conductor formed in each ceramic green sheet) or the like. ..

<Base metal layer forming step>
Next, as shown in FIG. 2B, the entire surface of the ceramic substrate 3 having the Au metallized layer 11 on the first main surface 7 side and the entire surface of the second main surface 9 side are respectively covered. The underlying metal layers 21 and 23 having conductivity are formed.

Specifically, first, Ti layers 21a and 23a made of Ti are formed over the entire surface on both sides of the first main surface 7 side and the second main surface 9 side by sputtering. The thickness of each of the Ti layers 21a and 23a is, for example, 0.2 μm.

Next, Cu layers 21b and 23b made of Cu are formed on the entire surfaces of the Ti layers 21a and 23a by sputtering. The thickness of each of the Cu layers 21b and 23b is, for example, 0.5 μm.

The base metal layers 21 and 23 are formed to ensure electrical continuity between the Au metallization layer 11 and the power supply and perform electrolytic plating.
<Resist forming process>
Next, as shown in FIG. 4, a photosensitive resist solution 33 is applied to each of the first main surface 7 side and the second main surface 9 side of the ceramic substrate 3 on which the base metal layers 21 and 23 are formed. Apply over the entire surface.

Specifically, the photosensitive resist liquid 33 is dripped from the liquid supply device 31 onto the roll coater 39, and the roll coater 39 is rotated in the direction of arrow A to adhere the photosensitive resist liquid 33 to the surface of the roll coater 39.

Further, the ceramic substrate 3 is arranged at a predetermined position of the plate 37 made of metal, the plate 37 is placed on the belt conveyor 35, and the roll coater 39 is brought into contact with the plate 37, and the belt conveyor 35 is driven to drive the plate 37. To move in the direction of travel.

Through this process, the roll coater 39 applies the photosensitive resist liquid 33 onto the ceramic substrate 3. It should be noted that this coating step is similarly performed on the first main surface 7 side and the second main surface 9 side.

After that, as shown in FIG. 2C, the photosensitive resist solution 33 is dried, and the plating resist (resist mask) 25 is formed so as to cover the underlying metal layers 21 and 23 (specifically, the Cu layers 21b and 23b). , 27 are formed.

<Resist removal process>
Next, as shown in FIG. 2D, the first main surface 7 side of the ceramic substrate 3 is exposed. Note that the exposure is performed on the portion where the resist mask 25 is desired to be removed, but here, the entire surface is exposed on the first main surface 7 side.

Then, the resist mask 25 on the first main surface 7 side is immersed in a developing solution to remove the resist mask 25 on the first main surface 7.
<Etching process>
Next, as shown in FIG. 3A, the underlying metal layer 21 on the first major surface 7 side is removed by etching.

That is, the base metal layer 21 is removed by performing an etching process using a well-known etching solution (for example, an inorganic acid or an organic acid).
<First surface layer forming step>
Next, as shown in FIG. 3B, a Ni—Co plated layer 13 is formed by electrolytic plating so as to cover the surface of the Au metallized layer 11.

Electrolytic plating is performed using the apparatus shown in FIG.
Specifically, the Ni electrode 45 is connected to the anode 43 of the DC power supply 41, and the object to be plated (here, the ceramic substrate 3 obtained by the etching step) HM is connected to the cathode 47. In the plated object HM, an electrically conductive portion (eg, via, internal wiring layer, underlying metal layer 23) is configured so that the cathode 47 and the Au metallized layer 11 are electrically connected. ..

Then, the Ni electrode 45 and the object to be plated HM are placed in a plating solution 49, and a voltage is applied by a DC power supply 41 to perform well-known electrolytic plating. As the plating solution 49, a plating solution containing Ni ions and Co ions, for example, a plating solution having a Co content of less than 40 mass% (including Co) as a mass ratio of Ni and Co is used.

As the plating conditions, for example, an applied voltage of 0.20 to 1.00 A/dm ² , a plating time of 60 min, a plating solution temperature of 40 to 50° C., and the like can be adopted.
<Second surface layer forming step>
Next, as shown in FIG. 3C, an Au plating layer 15 is formed by electrolytic plating so as to cover the surface of the Ni—Co plating layer 13.

Electrolytic plating is performed using the same apparatus as that shown in FIG. 5, and will be described with reference to FIG.
Specifically, the Pt electrode 46 is connected to the anode 43 of the DC power supply 41, and the object to be plated (here, the ceramic substrate 3 obtained up to the first surface layer forming step) HM is connected to the cathode 47.

Then, the Pt electrode 45 and the object to be plated HM are placed in a plating solution 49, and a voltage is applied by a DC power supply 41 to perform well-known electrolytic plating. As the plating solution 49, a plating solution containing Au ions is used.

As the plating conditions, for example, an applied voltage of 0.10 to 0.50 A/dm ² , a plating time of 90 sec, a plating solution temperature of 60 to 70° C., and the like can be adopted.
As a result, the wiring 5 is formed on the first main surface 7 of the ceramic substrate 3.

<Post process>
Next, as shown in FIG. 3D, the ceramic substrate 3 on which the wiring 5 is formed is immersed in acetone to remove the resist mask 27 on the second main surface 9 side.

After that, as shown in FIG. 3E, the underlying metal layer 23 is removed by using an etching solution such as an inorganic acid or an organic acid to complete the ceramic wiring board 1.
[1-3. effect]
Next, effects of the method for manufacturing the ceramic wiring board 1 of the present embodiment will be described.

According to the method for manufacturing the ceramic wiring board 1 of the present embodiment, the Au metallized layer 11, which is a conductor layer containing Bi and containing Au as a main component, is formed on the ceramic substrate 3 in the conductor layer forming step.

Further, in the first surface layer forming step, the Ni—Co plated layer 13 as the first surface layer is formed by electrolytic plating so as to cover the entire surface of the Au metallized layer 11.
Further, in the second surface layer forming step, the Au plating layer 15 as the second surface layer is formed by electrolytic plating so as to cover the entire surface of the Ni—Co plating layer 13.

That is, in this embodiment, since the Ni—Co plating layer 13 is formed on the Au metallization layer 11 by electrolytic plating, the Au metallization layer 11 is a catalyst poison (that is, a catalyst poison in electroless Ni plating). Even if Bi is contained, the Ni—Co plated layer 13 can be preferably formed.

Further, in the present embodiment, even if Bi or a compound thereof (for example, a component that becomes a catalyst poison) is added to the material of the Au metallized layer 11, it is difficult to adversely affect the formation of the Ni—Co plated layer 13. The effect of adding these substances can be exhibited. For example, by adding Bi or a compound thereof, the bondability between the Au metallized layer 11 and the ceramic substrate 3 can be improved.

Further, in the present embodiment, since the Ni—Co plated layer 13 is formed on the Au metallized layer 11 by electrolytic plating, there is a problem when Ti is used in the conventional sputtering (that is, eddy current loss in a high frequency band). Has the advantage that it is less likely to occur).

[2. Other Embodiments]
Needless to say, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the present invention.

(1) For example, in the first surface layer forming step, the first surface layer made of an alloy such as a Ni—Co plated layer is formed by electrolytic plating. The first surface layer may be formed.

(2) When the first surface layer is formed of a Ni alloy, Ni-Co, Fe-Ni, Fe-Cr-Ni or the like can be used as the Ni alloy.
(3) In the second surface layer forming step, the second surface layer such as the Au plating layer may be formed by any one of electroless plating, sputtering, vapor deposition, and thermal spraying, in addition to electrolytic plating. Good.

(4) When the second surface layer is formed, the second surface layer may be formed of Au alloy instead of Au alone.
Examples of the Au alloy of the second surface layer include Au-Cu, Au-Ag, Au-Co, Au-Ni, Au-Cu-Ag, Au-Cu-Cd, Au-Cu-Cd-Ag, and the like. Can be adopted. Further, as the composition (mass ratio) of each Au alloy, it is possible to adopt a range in which the content of components other than Au is 10% by mass or less.

(5) In the subsequent step of the embodiment, a resist mask is formed on the first main surface side in order to protect the wiring on the first main surface side, and then the underlying metal layer on the second main surface side is removed. May be. In this case, after removing the base metal layer on the second main surface side, the ceramic substrate provided with the resist mask on the first main surface side is immersed in acetone to remove the resist mask.

(6) It is also possible to appropriately combine the constituent elements of the above-described embodiments.

DESCRIPTION OF SYMBOLS 1... Ceramic wiring board 3... Ceramic substrate 5... Wiring 7... 1st main surface 9... 2nd main surface 11... Au metallized layer (conductor layer)
13... Ni-Co plating layer (first surface layer)
15...Au plating layer (second surface layer)
21, 23... Base metal layer 25, 27... Plating resist (resist mask)

Claims (3)

In a method for manufacturing a ceramic wiring board in which wiring is formed on the ceramics board,
As the step of forming the wiring,
A conductor layer forming step of forming, on the ceramic substrate, a conductor layer containing at least one of Bi, Pb, Cu, Sn, Zn and W, or a compound thereof, and containing Au as a main component;
A first surface layer forming step of forming a first surface layer made of Ni or a Ni alloy by electrolytic plating so as to cover the surface of the conductor layer;
A second surface layer forming step of forming a second surface layer made of Au or an Au alloy so as to cover the surface of the first surface layer;
A method for manufacturing a ceramics wiring board, comprising: The ceramic according to claim 1, wherein in the second surface layer forming step, the second surface layer is formed by any one method of electrolytic plating, electroless plating, sputtering, vapor deposition, and thermal spraying. Wiring board manufacturing method. Between the conductor layer forming step and the first surface layer forming step,
An underlying metal layer having conductivity is formed so as to cover the surface of the ceramic substrate on which the conductor layer is formed on the first main surface side and the surface of the second main surface opposite to the first main surface. A base metal layer forming step,
A resist forming step of forming a plating resist so as to cover the surface of the underlying metal layer on the first main surface and the second main surface;
A resist removing step of removing the plating resist on the first main surface side,
An etching step of removing the underlying metal layer on the first main surface side by etching;
The method for manufacturing a ceramic wiring board according to claim 1 or 2, further comprising:

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