JPH1065297A - Ceramic board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a discoloration, which is generated in electroless Au-plated layers or an electroless Au-plated layer, when an IC chip is bonded to a ceramic board at about 450 deg.C, in the ceramic board, which has lower electroless Ni- plated layers, upper electroless Ni-plated layers and the electroless Au-plated layers in the order of the low electroless Ni-plated layers, or in the ceramic board, which has an electroless Ni-plated layer and the electroless Au-plated layer on a connection member. SOLUTION: In the case where this board 10 has metallized layers 2 and 3 formed on the surface of the board 10, lower electroless Ni-plated layers 2a and 3a, which are respectively formed on the layers 2 and 3, upper electroless Ni-plated layers 2b and 3b, which are respectively formed on the layers 2a and 3a, and electroless Au- plated layers 2c and 3c, which are respectively formed on the layers 2b and 3b, in this order of the layers 2 and 3, the layers 2a and 3a, the layers 2b and 3b and the layers 2c and 3c, the layers 2b and 3b are crystallized. Or an electroless Ni-plated layer 5b and an electroless Au-plated layer 5c are provided in this order of the layer 5b and the layer 5c on a connection member 5, formed on the surface of this board 10 and the layer 5b is crystallized. As a method of crystallizing the layers 2b and 3b or the layer 5b, it is preferable to heat the layers 2b and 3b or the layer 5b at 500 to 750 deg.C in a reducing atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic substrate having an electroless Ni plating layer and an electroless Au plating layer, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A metallized layer formed of a high melting point metal such as tungsten or molybdenum provided on the surface of a ceramic substrate is used to directly bond (die attach) an IC (integrated circuit) chip or wire bond an Au wire or an Al wire. It is difficult. Therefore, electroless Ni plating such as Ni-Co plating or electroless Ni such as Ni-B or Ni-P plating.
Plating, and further, by electrolytic or electroless plating,
u-plated.

Meanwhile, electrolytic plating has advantages such as good plating quality, high plating formation speed, and easy management of plating solution. However, since it is necessary to apply a potential to the metallized layer on which plating is to be applied, it is necessary to take measures such as forming a tie bar for electrolytic plating on the substrate surface or in the substrate. On the other hand, electroless plating does not require the above-mentioned tie bars and the like, so it is possible to easily perform plating on a fine metallized layer and the like, and to perform plating on a substrate having an electrically independent metallized layer. Used.

[0004] In a ceramic substrate of a type in which external connection terminals such as pins and leads made of 42Ni-Fe alloy or Kovar are fixed on a metallized layer with a brazing material such as silver solder, a metallized layer made of tungsten or the like is used. It is difficult to directly braze the external connection terminals with a brazing material. Therefore, first, electrolytic or electroless Ni plating is applied to the metallized layer, and then external connection terminals are brazed. Further, Au plating is performed after Ni plating is performed on the solder and the external connection terminals. Accordingly, the metallized layer has a three-layer structure in which two Ni plating layers (hereinafter, also referred to as a lower Ni plating layer and an upper Ni plating layer, respectively) and an Au plating layer are formed. On the other hand, the external connection terminal has a two-layer structure including one Ni plating layer and Au plating layer.

[0005]

However, for example, an upper electroless Ni-P plating layer and an electroless Au plating layer are formed on a lower Ni plating layer formed on a metallized layer of a substrate to form a die pad or a wire bonding pad. age,
Thereafter, the IC chip is heated to about 450 ° C. and the IC chip is Au-S
i-Soldering to the die pad of the substrate, Au-S
The Au plating layer of an external connection terminal such as a die pad, a wire bonding pad, and a pin that was not covered with the i-wax may be discolored to brown, resulting in poor appearance.
In addition, the bonding strength of the discolored bonding pad portion may be insufficient at the time of wire bonding of an Al wire or the like. In addition, this discoloration occurs not only in the plating layer on the metallized layer but also in a connecting member that is plated after being connected to a substrate such as an external connection terminal, a seal ring, and a heat sink. This is because the Ni component in the electroless Ni-P plating layer diffused into the Au plating layer due to heating during bonding.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a ceramic substrate having a plating layer which does not cause discoloration even when heat is applied at the time of bonding an IC chip, and a method of manufacturing the same. is there.

[0007]

According to another aspect of the present invention, a ceramic substrate according to the present invention comprises a lower electroless Ni plating layer on a metallized layer formed on the substrate surface. And a ceramic substrate having an upper electroless Ni plating layer and an electroless Au plating layer in this order, wherein the upper electroless Ni plating layer is crystallized.

[0008] Here, the metallized layer is a layer provided for metallizing a part of the substrate surface.
Examples thereof include those made of a high melting point metal such as W, Mo, and Mo-Mn. Note that the metallized layer may be formed simultaneously with firing of the ceramic substrate, that is, by simultaneous firing.
It may be baked after firing the ceramic substrate. The electroless Ni plating layer means not only pure Ni but also Ni-P, Ni-
It also means an electroless plating layer made of a Ni alloy containing Ni as a main component such as B. The electroless Au plating layer also includes an electroless plating layer made of an Au alloy containing Au as a main component, in addition to pure Au plating.
Further, there are a substitution type, a reduction type, and the like in the electroless Au plating, and any method is included as long as it is an electroless plating method, and both may be used in combination.

Further, the term "crystallized" in the present invention refers to a state in which most of Ni, P, B, and the like deposited by plating constitute crystals. When the plating layer is analyzed by an X-ray diffraction method (thin film X-ray diffractometer), sharp peaks of crystals of Ni, Ni ₃ P, Ni ₃ B, etc. are observed, and diffraction peaks of Ni, etc. are observed. This is a state in which the X-ray intensity at an angle sufficiently separated from the angle (hereinafter, also referred to as “baseline intensity”) and the intensity at the bottom of the valley between diffraction peaks of Ni or the like are substantially the same. In other words, when viewing the graph of the diffraction intensity, the presence of a gentle peak (bump) detected by the presence of amorphous Ni or the like is not observed, but a sharp diffraction peak indicating the presence of a crystal of Ni or the like. Only the state where it is observed.

[0010] As described above, the discoloration is caused by the Ni in the upper electroless Ni plating layer due to the heating during the bonding of the IC chip.
Is to diffuse into the Au plating layer. This is because Ni deposited by electroless plating or Ni alloy such as Ni-P is dissociated and precipitated from components such as complex salts in the plating solution due to the nature of electroless plating. Is formed. Therefore, the amorphous phase is not crystallized at the stage of simple deposition and is unstable.
Is easily diffused. However, as in the present invention,
When the upper electroless Ni plating layer is crystallized, Ni becomes a stable Ni plating layer that is difficult to diffuse, and even when heated at the time of bonding an IC chip, diffusion of Ni into the electroless Au plating layer is suppressed, A substrate that does not cause discoloration in the Au plating layer on the metallized layer can be obtained. Also, the lower electroless N
Since the crystallized upper electroless Ni plating layer is formed on the i-plating layer, the upper electroless Ni plating layer is firmly fixed to the lower electroless Ni plating layer and does not peel off.

Further, the ceramic substrate according to claim 2 is characterized in that the upper electroless Ni plating layer is a Ni-P plating layer.

[0012] The electroless Ni-P plating layer and the electroless Au plating layer have high adhesion strength, and no trouble such as blistering occurs at the interface between them. Further, an electroless Au plating layer can be easily formed on the electroless Ni-P plating layer.

Further, the ceramic substrate according to claim 3 is a ceramic substrate having an electroless Ni plating layer and an electroless Au plating layer in this order on a connecting member formed on the surface of the substrate. It is characterized in that the electroless Ni plating layer is crystallized.

Here, the connection member refers to a member to be connected to the substrate, which is plated after the connection to the substrate, and more specifically, a member for sealing an external connection terminal and a lid. Examples include a seal ring and a heat sink for heat dissipation. The external connection terminal corresponds to a connection terminal used to connect the ceramic substrate to another ceramic substrate, a printed circuit board, or the like, and corresponds to a pin, a lead, or the like. As the material of the connection member, for example, 42Ni-Fe alloy, Kovar,
Cu-W alloy, Cu-Mo alloy and the like can be mentioned. Also,
The connecting members include those in which these materials are plated in advance with Ni and connected to a substrate.

As described above, the cause of discoloration is that Ni in the electroless Ni plating layer becomes A due to heating at the time of bonding the IC chip.
This is for diffusing into the u plating layer. This may be Ni deposited by electroless plating or Ni such as Ni-P.
The alloy is formed by dissociating and depositing Ni and the like from components such as complex salts in the plating solution due to the nature of electroless plating. Therefore, it is not crystallized at the stage of being simply adhered and has an unstable amorphous shape, and Ni is easily diffused by heating. However, according to the present invention, the electroless Ni plating layer, which is the base of the electroless Au plating layer, is crystallized and is a stable Ni plating layer that is difficult to diffuse, so that it is heated during bonding of the IC chip. Even if this is done, the diffusion of Ni into the electroless Au plating layer is suppressed, and a substrate can be obtained in which the Au plating layer does not discolor even in the connection member. In addition, since the crystallized electroless Ni plating layer is formed on the connection member, the electroless Ni plating layer is firmly fixed to the connection member and does not peel off.

The ceramic substrate according to claim 4 is characterized in that the electroless Ni plating layer is a Ni-P plating layer.

Ni- as an underlayer of the electroless Au plating layer
Since the P plating layer is crystallized, Ni in the Ni—P layer is unlikely to diffuse, and even if heated at the time of bonding the IC chip, diffusion into the electroless Au plating layer is suppressed, so that a substrate that does not cause discoloration. It can be. In addition, an electroless Au plating layer can be formed on the Ni-P layer with high adhesion strength, and no trouble such as blistering occurs at the interface between them. Further, an electroless Au plating layer can be easily formed on the Ni-P layer.

Further, in the method of manufacturing a ceramic substrate according to the present invention, a step of forming a lower electroless Ni plating layer on a metallized layer formed on the substrate;
forming an upper electroless Ni plating layer on the i-plating layer;
A step of heating at about 750 ° C. for crystallization; and a step of forming an electroless Au plating layer directly on the crystallization upper electroless Ni plating layer.

By heating at 500 to 750 ° C. for crystallization, the upper electroless Ni plating layer, which was amorphous before heating, is crystallized and stabilized. Therefore, then 4
Even if heating is performed at about 50 ° C., diffusion of Ni in the upper electroless Ni plating layer into the electroless Au plating layer is suppressed, and therefore, no discoloration occurs. Further, since heating in a reducing atmosphere was used as a crystallization method, the upper electroless N
The crystallization process is easy and reliable while preventing oxidation of the i-plated layer. In addition, the lower electroless Ni plating layer has a lower electroless Ni plating layer under the upper electroless Ni plating layer.
At a temperature of 0 ° C., the two are in close contact with each other and no peeling occurs.

Preferably, a Ni-P plating layer is formed as the upper electroless Ni plating layer.
This is because an electroless Au plating layer can be easily formed on the Ni-P layer. Further, the electroless Au plating layer can be formed on the Ni-P layer with high adhesion strength, and no trouble such as blistering occurs at the interface between the two. Prior to forming the upper electroless Ni plating layer, it is preferable to heat the lower electroless Ni plating layer to further strengthen the adhesion with the metallized layer. The heating is preferably performed at a temperature of 700 ° C. or higher, and may be replaced by the heating in the brazing step of the connecting member using a brazing material such as silver brazing.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a ceramic substrate, wherein the connecting member formed on the substrate is formed by electroless Ni.
A step of forming a plating layer, a step of heating the electroless Ni plating layer at 500 to 750 ° C. in a reducing atmosphere to crystallize, and a step of directly forming an electroless Au plating layer on the crystallized upper electroless Ni plating layer. Forming a step.

By heating at 500 to 750 ° C. for crystallization, the amorphous electroless Ni—P plating layer, which was amorphous before heating, is crystallized and stabilized. Therefore, then 4
When the heating is performed at about 50 ° C., the diffusion of Ni in the electroless Ni plating layer into the electroless Au plating layer is suppressed, and therefore, the discoloration of the Au plating layer does not occur. In addition, since heating in a reducing atmosphere was used as a crystallization method,
Crystallization can be easily and reliably performed while preventing oxidation of the electroless Ni plating layer.

It is more preferable to form an Ni-P plating layer as the electroless Ni plating layer. Ni
This is because an electroless Au plating layer can be easily formed on the -P layer. Further, the electroless Au plating layer can be formed on the Ni-P layer with high adhesion strength, and no trouble such as blistering occurs at the interface between the two.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a ceramic substrate 10.
FIG. The ceramic substrate 10 has a substantially square shape in a plan view, has a concave portion 1 having a stepped cross section substantially in the center, and a bottom portion forms a die pad 2 for joining an IC chip (not shown). In addition, bonding pads 3 for connecting to an IC chip by wires are arranged in rows above the surrounding stairs, extending from wirings (not shown) inside the substrate with their tips facing the die pad 2 side. .
Further, a connection pad 4 for connecting a terminal is formed on the upper surface 10a of the substrate 10, and the connection pad 4 is connected to a wiring inside the substrate by a via V extending upward from the inside of the substrate in the drawing.

Here, the ceramic substrate 10 is formed by a well-known ceramic green sheet forming technique, a thick film printing technique, and a co-firing technique. That is, a ceramic green sheet mainly composed of alumina formed by a known method is punched into a predetermined size, and a via hole is formed. Thereafter, the via holes are filled with a refractory metal paste containing tungsten or molybdenum as a main component, and the refractory metal paste is printed on the sheet surface in a predetermined pattern. The sheets were laminated and pressed in a predetermined order, and were simultaneously fired at about 1600 ° C. in a humid hydrogen atmosphere to form a ceramic substrate 10. Therefore, each of the die pad 2, the bonding pad 3, and the connection pad 4 is a metallized layer made of a refractory metal.

The die pad 2 of the ceramic substrate 10
Pd nucleation was performed on the bonding pad 3 and the connection pad 4. For Pd nucleation, Pd-
By washing the substrate after immersing the substrate in the five liquids, P serving as a nucleus of electroless plating is formed only on each metallized layer.
d remained. After that, using an electroless Ni-P plating solution (Uemura Kogyo Co., Ltd. Nimden 78S, medium phosphorus type)
As shown in the enlarged cross-sectional view of FIG. 2A, the lower Ni layer having a thickness of 0.5 to 2.0 μm is immersed in the plating solution and formed on each metallized layer (die pad 2, bonding pad 3, connection pad 4). -P layers 2a ', 3a', and 4a 'were formed, respectively.

Next, a nail head type pin-shaped terminal 5 as an external connection terminal is brazed to the connection pad 4 of the ceramic substrate 10 via a lower Ni-P layer 4a 'by a silver brazing material 6 (FIG. 2 ( B)). Where the lower Ni
The -P layer 4a 'is provided for covering the metallized layer made of a high melting point metal which is hardly wetted by the brazing material so as to enable brazing. In addition, since it is heated to about 800 ° C. by brazing, each of the lower Ni—P layers 2a ′, 3a ′,
a ′ is crystallized and stabilized to form crystallized lower Ni—P layers 2a, 3a, and 4a, respectively. Further, the crystallized lower Ni-P layers 2a, 3a, 4a are firmly adhered to the metallized layers 2, 3, 4.

Further, in the same manner as described above, the upper Ni-P layers 2b ', 3b' and N on the crystallized lower Ni-P layers 2a, 3a and the terminals 5 and the silver brazing material 6 by electroless plating.
The i-P layers 5b 'are each formed to a thickness of 1.5 to 5.0 [mu] m (see FIG. 3A). This upper Ni-P layer and Ni
The -P layer serves as a base for the Au plating layer described later.

Next, the ceramic substrate 10 is placed in a belt furnace under a reducing atmosphere of a 75% hydrogen + nitrogen mixed gas.
The upper Ni-P layer and the Ni were heated at a maximum temperature of 500 to 750 ° C. and a maximum temperature holding time of 5 minutes.
The −P layer was crystallized into a crystallized upper Ni—P layer 2b, 3b and a crystallized Ni—P layer 5b, respectively (FIG. 3).
(B)).

Further, as shown in FIG. 4, the ceramic substrate 10 after the heat treatment is replaced with a substitution type electroless Au plating solution (N.
After immersion in Echemcat Co., Ltd., Atmex), substitutional Au plating (thickness: about 0.05 μm), and then immersion in reduced electroless Au plating solution (Kolet, Kobayashi Chemical Co., Ltd.) The crystallization upper Ni-P layer 2b,
3b and the Au layer 2 on the crystallized Ni-P layer 5b, respectively.
c, 3c, and 5c were formed to a thickness of 0.5 to 2.0 μm (total thickness).

Thus, the metallized layer (die pad,
On the bonding pads 2 and 3, the crystallized lower Ni-P layers 2a and 3a, the crystallized upper Ni-P layer 2b,
3b and Au layers 2c and 3c are formed.
A crystallized Ni-P layer 5b and an Au layer 5c
Is formed. The Ni-P layer and the Au layer were firmly adhered to each other, and there was no occurrence of blisters at the interface between them. In addition, as comparative examples, only the above-mentioned heat treatment of the Ni-P layer was not performed, and the other heat treatments were the same, and heat treatments with maximum temperatures of 300, 400, and 800 ° C. were also manufactured.

Then, assuming the conditions at the time of bonding the IC chips, a heating test was performed in an air atmosphere at a maximum temperature of 450 ° C.
° C, the maximum temperature holding time is 3 minutes, and each Au layer 2
Changes in the color tone of c, 3c and 5c were observed. The presence or absence of discoloration was judged to be discolored ants when brown color unevenness and color tone difference occurred in at least a part of the Au layer presenting a golden color. Table 1 shows the results.

[0033]

[Table 1] * When heated at 800 ° C., melting of the silver brazing material occurred.

As is clear from the results in Table 1, when no heat treatment was performed (Comparative Example 1) and when the temperature was as low as 300 ° C. or 400 ° C. even after the heat treatment (Comparative Examples 2 and 3), In all the samples, discoloration occurs in the Au layer. This is different from electrolytic plating in which the film thickness increases while growing crystals. In electroless plating, amorphous particles are deposited and the film thickness increases. Therefore, Ni of the electroless Ni—P plating layer is not stable, and is easily diffused by heat. Further, since the Au layer is also formed by electroless plating, it is easy for Ni to diffuse and enter. Therefore, when bonding the IC chip,
It is considered that Ni is diffused into the Au layer to cause discoloration when is heated or in a heating test.

On the other hand, in order to prevent this discoloration, it is sufficient to crystallize and stabilize amorphous particles formed by electroless plating in advance, and it is found that heating at 500 ° C. or more is sufficient. As can be seen from the above results, if heating is performed at 500 ° C. or more, no discoloration occurs,
This is in sharp contrast to the case of heating below ℃, indicating the effectiveness of heating and crystallization. Note that 7
When heating at a temperature exceeding 50 ° C. (Comparative Example 4),
In addition to the problem that the brazing material connecting the terminals is melted (melting point of eutectic silver brazing is about 780 ° C.), the cost is increased if the heating temperature is high. The maximum temperature applied to the ceramic substrate 10 at the time of IC bonding is about 450 ° C., and it is sufficient to perform the processing at a lower temperature within a range in which discoloration does not occur.

In order to confirm this, 500 ° C., 6
The samples (Examples 1, 2, and 3) heat-treated at 00 ° C. and 700 ° C., respectively, and the sample not subjected to the heat treatment (Comparative Example 1) were subjected to a state before Au plating.
The crystal structure of the upper crystallized Ni-P plating layer (Comparative Example 1 was the upper Ni-P plating layer) was investigated by the following method.
The investigation was conducted using a thin film X-ray diffractometer LAD- manufactured by Rigaku Corporation.
Using an RB, an X-ray wavelength of 1.540562 angstroms (C
u: Kα1), acceleration voltage 40 kV, current 200 mA, X
Assuming that the line incident angle is 5.0 deg, the intensity of the diffracted X-ray is
θ was measured in the range of 10 to 70 degrees. Table 2 shows the angle 2θ (theoretical value) and the peak intensity corresponding to each crystal diffraction peak.
Shown in 5 to 8 show the intensity profile of the diffraction X-ray, peak data indicating the position and intensity of the diffraction peak calculated from the profile, and the theoretical diffraction peak data of the corresponding substance, respectively. Note that the diffraction peak obtained from the profile appears slightly shifted from the theoretical diffraction peak. This is because the elements constituting the crystal such as Ni ₃ P have a theoretical mixing ratio (for Ni ₃ P, N
(i: P = 3: 1), the crystal grows from a state that is not (i: P = 3: 1), and it is considered that the components in the crystal slightly deviate from the theoretical mixing ratio. Therefore, in Table 2 below,
As the diffraction X-ray angle 2θ, the theoretical diffraction peak angle was represented as a representative.

[0037]

[Table 2]

As is clear from Table 2 and FIGS. 5 to 8, when no heating is performed (see FIG. 8), the angle is 43.6.
Although a crystal diffraction peak of Ni ₃ P is observed at 24 degrees (peak number 5) and the like, a gentle diffraction peak (bump) is observed as a whole at an angle of 35 to 55 degrees. In addition, the intensity at an angle of 44.505 degrees (peak number 6) indicating the presence of Ni crystals is small (3236 cps). These indicate that the component Ni or the like is not in a crystalline state but in an amorphous state. That is, it can be seen that although crystals such as Ni ₃ P exist partially, they are not in a crystalline state as a whole.

On the other hand, in the case of heating to 500 ° C. (FIG. 5), the crystal diffraction peak of Ni, which was almost no in the case of no heating (FIG. 8), was strongly increased to 45.505 ° (peak number 6). Appear and form a sharp diffraction peak. The diffraction peaks of Ni ₃ P are also 41.762 degrees (peak number 3), 43.624 degrees (5), and 46.6 degrees.
It appears strongly at 08 degrees (9). From this, 5
By the heat treatment at 00 ° C., the component of Ni-P plating is Ni
And Ni ₃ P crystal.

In FIG. 8, a gentle diffraction peak exists at an angle of 35 to 55 degrees. However, in FIG. 5, the angle 37 between peak numbers 1 and 2
４７40 degrees and angle 47 between peak numbers 9 and 10
The intensity around 50 degrees is, for example, almost the same value as the intensity around 20 degrees or 60 degrees (baseline intensity). In addition, between each diffraction peak (for example, around 42 degrees between the diffraction peaks of 41.762 degrees (peak number 3) and 42.821 degrees (peak number 4), 45.208 degrees (peak number 7) and 46 degrees The intensity at the bottom of the valley at 0.008 degrees (around 46 degrees between the diffraction peaks at peak number 8) is almost the same as the baseline intensity. Therefore, it is considered that a gentle diffraction peak as shown in FIG. 7 does not exist. That is, it indicates that amorphous Ni or the like does not exist (or is extremely small).

Similarly, as shown in Table 2 and FIG.
Even when heated to 00 ° C., the crystal diffraction peak of Ni strongly appears at 44.505 degrees (peak number 6). Similarly, the diffraction peak of Ni ₃ P is also 41.76.
2 degrees (peak number 3), 43.624 degrees (5), 4
6.608 degrees (9). In addition, 4
1.762 ° (peak number 3) diffraction peak at 500 ° C
It appears more strongly than in the case of. This is presumed to be because the crystal direction in which Ni ₃ P grows easily varies depending on the temperature of the heat treatment. In any case, it can be seen that the heat treatment at 700 ° C. turned the Ni-P plating components into Ni crystals and Ni ₃ P crystals.

Also, in FIG. 7, the intensity around 37 to 40 degrees and around 47 to 50 degrees have almost the same value as the baseline intensity around 20 degrees and 60 degrees. Also, as in the case of FIG. 5, the intensity of the valley bottom between the diffraction peaks is almost the same as the baseline intensity. Therefore, it is considered that a gentle diffraction peak as shown in FIG. 7 does not exist. That is, it indicates that amorphous Ni or the like does not exist (or is extremely small). The same can be read from Table 2 and FIG. 7 when heating to 600 ° C.

From these results, it was confirmed that when heat treatment was performed at 500 ° C., 600 ° C., and 700 ° C., the upper Ni—P plating layer was crystallized to become the upper crystallized Ni—P plating layer. Was done. Then, when an Au layer is provided by plating on the upper crystallized Ni—P plating layer crystallized in this way, connection of an IC chip or 450 ° C.
Since the discoloration of the Au layer does not occur in the heating test for 3 minutes, unstable Ni changes to Ni crystal or Ni ₃ P crystal and becomes stable by crystallizing the Ni—P plating layer, and Au becomes stable. It can be seen that diffusion into the layer is suppressed.

It should be noted that comparing FIGS. 5 to 7 shows that there is almost no difference, and it can be seen that a heat treatment at 500 ° C. is sufficient for crystallization, and that discoloration is also sufficiently prevented. Therefore, in consideration of variation in the degree of crystallization due to variation in the temperature and time of the heat treatment, the treatment may be performed at a temperature as low as possible, and if the treatment is performed at a low temperature, the cost of the heat treatment can be reduced. .

In the above-described embodiment, an example is shown in which the lower Ni-P layers 2a ', 3a', and 4a 'are also formed by electroless Ni-P plating. Ni or Ni-
A Co layer may be formed. Moreover, you may form by electroless Ni-B plating or Ni-BP plating. Also,
Although the example in which the upper Ni-P layer is provided directly on the crystallized lower Ni-P layer has been described, the upper Ni-P layer is formed by forming the upper Ni-P layer with an electroless Ni-B plating layer interposed. An appropriate intervening layer may be provided as a lower layer according to the material of the metallized layer. Further, in the above embodiment, an example in which the upper Ni-P layer is formed by electroless plating has been described, but instead of Ni-P, N (pure Ni), Ni-B, Ni-P-B, or other N
An upper layer made of an i-alloy may be formed. Also in this case, diffusion of Ni into the Au layer due to crystallization can be suppressed.

In the above embodiment, an example in which crystallization is performed by heat treatment using a heating furnace has been described, but the crystallization method is not limited to this. For example, irradiation of a laser beam having an appropriate energy directly
The i-P layers 2b ', 3b', and 5b 'may be heated and crystallized. In this case, since the entire substrate is not heated, it is suitable for a substrate that does not want to be heated or a substrate in which a capacitor, a resistor, or the like, whose characteristics and the like are expected to change due to heating, is built in or provided on the surface. Further, an electron beam may be similarly irradiated. However, when using an electron beam, it is necessary to put a substrate into a vacuum vessel.

[0047]

As is clear from the above, the upper electroless N
A ceramic that does not cause discoloration of the Au layer formed on the metallized layer or the connection member in the heat treatment or the heat test at the time of IC chip bonding because the i-plated layer or the electroless Ni-plated layer is crystallized. A substrate can be provided. In particular, when the upper electroless Ni plating layer or the electroless Ni plating layer is a Ni-P plating layer, an electroless Au plating layer can be formed on the Ni-P layer with high adhesion strength, and a fringe is formed at the interface between the two. And the like can be avoided. In addition, as a method thereof, crystallization may be performed by heating to 500 to 750 ° C. in a reducing atmosphere after electroless Ni plating, and a ceramic substrate can be supplied reliably, easily and inexpensively.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state before plating of a ceramic substrate and brazing of terminals.

FIG. 2 is a partially enlarged cross-sectional view showing Ni-P plating and brazing of pin-shaped terminals on various portions of a ceramic substrate.

FIG. 3 is a partially enlarged cross-sectional view showing a step of performing Ni-P plating and heat treatment on various portions of a ceramic substrate.

FIG. 4 is a partially enlarged cross-sectional view showing a step of applying Au plating to various portions of a ceramic substrate.

FIG. 5 is a graph showing X-ray diffraction analysis data of a sample at a heat treatment temperature of 500 ° C.

FIG. 6 is a graph showing X-ray diffraction analysis data of a sample at a heat treatment temperature of 600 ° C.

FIG. 7 is a graph showing X-ray diffraction analysis data of a sample at a heat treatment temperature of 700 ° C.

FIG. 8 is a graph showing X-ray diffraction analysis data of a sample without heat treatment (Comparative Example).

BRIEF DESCRIPTION OF THE REFERENCE NUMERALS 10: ceramic substrate 1: concave portion 2: die pad 3: bonding pad 4: connection pad 5: terminal 6: silver brazing material 2a, 3a, 4a: crystallized lower Ni-P layer 2b, 3b: Crystallized upper Ni-P layer 5b: crystallized Ni-P layer 2c, 3c, 5c: Au layer

Claims (6)

[Claims] 1. A metallized layer formed on a substrate surface,
A ceramic substrate having a lower electroless Ni plating layer, an upper electroless Ni plating layer, and an electroless Au plating layer in this order, wherein the upper electroless Ni plating layer is crystallized. Ceramic substrate. 2. The method according to claim 1, wherein the upper electroless Ni plating layer is made of Ni-P.
The ceramic substrate according to claim 1, wherein the ceramic substrate is a plating layer. 3. A ceramic substrate having an electroless Ni plating layer and an electroless Au plating layer in this order on a connecting member formed on the substrate surface, wherein the electroless Ni plating layer is crystallized. A ceramic substrate. 4. The ceramic substrate according to claim 3, wherein said electroless Ni plating layer is a Ni—P plating layer. 5. A step of forming a lower electroless Ni plating layer on a metallized layer formed on a substrate; a step of forming an upper electroless Ni plating layer on the lower electroless nickel plating layer; Electrolytic Ni plating layer in reducing atmosphere
A method of manufacturing a ceramic substrate, comprising: a step of heating at 50 ° C. for crystallization; and a step of forming an electroless Au plating layer directly on the crystallization upper electroless Ni plating layer. 6. An electroless Ni on a connecting member formed on a substrate.
Forming a plating layer; and forming the electroless Ni plating layer in a reducing atmosphere at 500 to 750.
A method of manufacturing a ceramic substrate, comprising: a step of crystallization by heating at a temperature of ° C .; and a step of forming an electroless Au plating layer directly on the crystallization upper electroless Ni plating layer.