JP7107591B2 - bonded substrate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a bonded substrate in which a copper material is bonded to the surface of a ceramic substrate.

A bonded substrate in which a copper material is bonded to the surface of a ceramic substrate is generally bonded with an active metal brazing material containing silver (see Patent Document 1).

Japanese Patent No. 3211856

However, while active metal brazing filler metals containing silver can be joined with sufficient strength, they are expensive as brazing filler metals because they contain silver. There is a problem that it is easy for migration to occur. Therefore, in joining a copper material to a ceramic substrate, there has been a demand for another joining method capable of achieving sufficient strength without using silver.

The present invention was made to solve the above problems, and its object is to provide a technique for realizing sufficient strength without using silver when bonding a copper material to a ceramic substrate. be.

In order to solve the above problems, the first aspect is a bonded substrate in which a copper material is bonded to the surface of a ceramic substrate made of a material containing nitrogen (N), the first layer containing titanium (Ti) as a main component. , a second layer mainly composed of copper (Cu) contained in the copper material, and a third layer composed of a compound of a part of the components contained in the ceramic substrate and titanium (Ti), the ceramic substrate , the first layer to the third layer are laminated in this order toward the copper material.

Further, the above aspect may be changed to a second aspect described below.

In the second aspect, the second layer has a maximum thickness of 0.1 μm or more.

Further, each of the above aspects may be changed to the third aspect shown below.

In the third aspect, when the thickness of the first layer is t1, the maximum thickness of the second layer is t2, and the thickness of the third layer is t3, the bonding layer has the thickness of the third layer and It is formed such that the ratio (t3/(t1+t2)) to the other layers is less than 7.

Further, each of the above aspects may be changed to a fourth aspect shown below.

In the fourth aspect, the bonding layer is bonded to the ceramic substrate at 5 N/mm or more.

Further, each of the above aspects may be changed to the fifth aspect shown below.

In the fifth aspect, the ceramic substrate is a substrate made of silicon nitride _{( Si3N4} ).

This aspect may be like the sixth aspect shown below.

In the sixth aspect, in the third layer, a compound of silicon (Si) and titanium (Ti) accounts for 50% by weight or more of the whole.

Further, each of the above aspects may be changed to a seventh aspect shown below.

In the seventh aspect, the joining layer has an elastic modulus of Young's modulus of 200 GPa or more.

With the bonded substrate of these aspects, as will be described later, the copper material can be bonded with sufficient strength to the surface of the ceramic substrate without using silver. Therefore, with this bonded substrate, an increase in cost due to silver is suppressed, and migration due to chemical reaction between silver and other substances present in the surroundings does not occur.

In order to solve the above problems, an eighth aspect is a bonding method for bonding a copper material to a surface of a ceramic substrate made of a material containing nitrogen (N), wherein the ceramic substrate and the plate-shaped copper material are bonded together. The titanium ( a first layer mainly composed of Ti), a second layer mainly composed of copper (Cu) contained in the copper material, and a compound of some components contained in the ceramic substrate and titanium (Ti) is laminated in order from the first layer to the third layer from the ceramic substrate toward the copper material.

This aspect may be like the ninth aspect shown below.

In the ninth aspect, the material in which the titanium material is sandwiched between the ceramic substrate and the plate-shaped copper material is fired under pressure in a temperature environment of 875° C. or higher for 3 hours or longer.

Also, the eighth and ninth aspects may be changed to the tenth aspect shown below.

In the tenth aspect, the titanium material used has a thickness of 1 μm or more.

This aspect may be like the eleventh aspect shown below.

In the eleventh aspect, the titanium material used has a thickness of 3 μm or more.

These 8th to 11th aspects are suitable for manufacturing the bonded substrates of the 1st to 7th aspects.

FIG. 2 is a perspective view showing a bonding substrate in the present invention; 1 is a front view showing a bonded substrate according to the present invention; FIG. FIG. 2 is a cross-sectional view of a cross section of the bonded substrate of the present invention, which intersects the direction in which it spreads, observed with an electron microscope (SEM). Front view showing a structure in which a titanium material is sandwiched between a ceramic substrate and a copper material Front view showing a jig and a furnace for manufacturing a bonded substrate

Embodiments of the present invention will be described below with reference to the drawings.
(1) Overall Configuration As shown in FIGS. 1 and 2, the bonded substrate 1 is formed by bonding a copper material 200 to the surface of a ceramic substrate 100 made of a material containing nitrogen (N). A bonding layer 300 is formed between 100 and copper material 200 to bond them together. In this embodiment, the ceramic substrate 100 is mainly composed of silicon nitride (Si ₃ N ₄ ).

As shown in FIG. 3, this bonding layer 300 is composed of three layers, namely, a first layer 10, a second layer 20 and a third layer 30, which extend from the ceramic substrate 100 toward the copper material 200. Layers 30 are laminated in order.

Among these bonding layers 300, the first layer 10 is a layer containing titanium (Ti) as a main component. In the present embodiment, the first layer 10 is a layer made of titanium (Ti) or a compound of nitrogen (N) and titanium (Ti) contained in the ceramic substrate 100, and has a thickness of 0.5 to 1.0 μm. It is formed with a thickness that averages a certain value.

The second layer 20 is a layer containing copper (Cu) contained in the copper material 200 as a main component. In this embodiment, the second layer 20 is formed as a layer having a maximum thickness of a specific value of 0.1 μm or more.

Also, the third layer 30 is a layer made of a compound of titanium (Ti) and some components contained in the ceramic substrate 100 .

Further, in the present embodiment, the third layer 30 is made of a compound of silicon (Si) and titanium (Ti) in the ceramic substrate 100, and the composition of this compound is 50% by weight of the total composition of the third layer 30. occupies more than The third layer 30 is formed with a thickness averaging a specific value in the range of 2 to 8 μm.

Further, the bonding layer 300 has a thickness of t1 for the average thickness of the first layer 10, t2 for the maximum thickness of the second layer 20, and t3 for the average thickness of the third layer 30. It is formed such that the ratio (t3/(t1+t2)) to the other layers is less than 7.

Also, the bonding layer 300 is bonded to the ceramic substrate 100 at 5 N/mm or more.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to the above embodiments, and it goes without saying that various forms can be taken as long as they fall within the technical scope of the present invention. .
(2) Manufacturing Method of Bonded Substrate 1 The bonded substrate 1 described above is manufactured by bonding a copper material 200 to the surface of a ceramic substrate 100 made of a material containing nitrogen (N).

Specifically, as shown in FIGS. 4 and 5, a sheet-like titanium material 400 is sandwiched between a ceramic substrate 100 and a plate-like copper material 200, and the structure 2 is thus sandwiched. is placed in a furnace 600 while being pressurized from above and below by a jig 500, and fired. In this way, the bonded substrate 1 in which the copper material 200 is bonded to the surface of the ceramic substrate 100 is manufactured.

Here, the ceramic substrate 100 is a substrate containing silicon nitride (Si ₃ N ₄ ) as a main component and having a thickness of 0.2 mm or more (0.25 mm or 0.32 mm in this embodiment). Moreover, the copper material 200 is a substrate having a thickness of 0.1 mm or more (0.2 mm in this embodiment). Also, the titanium material 400 is formed with a thickness that averages a specific value in the range of 3 to 10 μm.

Moreover, the firing of the structure 2 described above is performed in a temperature environment of 875° C. or higher (more specifically, 900° C.). The time required for firing is 3 hours or more (3 hours or 6 hours in this embodiment).

In the bonded substrate 1 manufactured in this manner, the first layer 10 to the third layer 30 are sequentially laminated from the ceramic substrate 100 toward the copper material 200 as the bonding layer 300 formed between the ceramic substrate 100 and the copper material 200. It becomes what was done.
(3) Evaluation of Bonded Substrate 1 The applicant of the present application prepared a plurality of samples (seven types in this embodiment) of bonded substrates manufactured using the same material under different bonding conditions. The bonding strength between the ceramic substrate 100 and the copper material 200 was measured.

First, seven types of bonded substrate samples were manufactured with different firing times (3 hours, 6 hours), firing temperatures (800°C, 900°C), and thicknesses of the titanium material 400 (3 μm, 5 μm, 10 μm). Then, the cross section of each (the cross section intersecting the direction in which the bonding substrate spreads) was observed with an electron microscope (SEM), and the thickness of each layer that became the bonding layer 300 was measured. It has been found that three layers, 1st layer 10 to 3rd layer 30, are formed.

Here, the average thickness of the first layer 10 and the third layer 30 was measured, and the maximum thickness of the second layer 20 was measured. Regarding the second layer 20, the thickness is measured after mechanical polishing and ion milling are performed on the cross section to form a region suitable for measurement.

The predetermined condition is a temperature (900° C. in this evaluation) equal to or higher than the eutectic temperature (875° C.) of titanium (Ti) and copper (Cu), and a sufficient time corresponding to the thickness of the titanium material 400. Only firing is performed. In other words, if the titanium material 400 is thin, a short firing time is sufficient (specifically, three hours or more in the case of 3 μm or 5 μm). (Specifically, 6 hours or more for 10 μm).

When the bonding strength between the ceramic substrate 100 and the copper material 200 was measured for each bonding substrate sample on which the bonding layer 300 was formed in this way, all of them, including the one having 8.5 N/mm, were 5 N/mm or more. It was confirmed that the bonding strength of 5 N/mm required for power semiconductor circuit boards and the like was satisfied.

Here, the joint strength of the samples in the present invention and the conventional one is measured by a 90-degree peel test (peel test). In this test, the copper material 200 and the bonding layer 300 did not peel off before the copper material 200 peeled off from the ceramic substrate 100 for any of the samples. It can be seen that the is joined more strongly.

Furthermore, it was found that the thickness of each layer of the bonded substrate on which the bonding layer 300 is formed has a specific relationship. When the thickness of the first layer 10 is t1, the maximum thickness of the second layer 20 is t2, and the thickness of the third layer 30 is t3, the ratio ( t3/(t1+t2)) is less than seven. In other words, it can be said that the bonding layer 300 is formed and a sufficient bonding strength is achieved when the respective layers are formed in such a relationship.

Here, the elastic modulus of the bonding layer 300 was also measured for each bonding substrate sample on which the bonding layer 300 was formed, and it was confirmed that the Young's modulus was 200 GPa or more. This elastic modulus is sufficiently larger than that of the conventional sample bonded with an active metal brazing material containing silver (around 100 GPa). In addition, this modulus of elasticity is measured with an indenter of a microindentation hardness tester (nanoindentation tester; ENT-2100 manufactured by Elionix Co., Ltd.) with respect to a cross section cut in a direction intersecting the plate-like spreading direction of the bonding substrate. is the result of measurement based on the depth of plastic deformation caused by pushing into the bonding layer 300 with a predetermined load. Such a high Young's modulus has the effect of suppressing the amount of warp as a bonded substrate.
(4) Effects As described above, the bonded substrate 1 of the above-described embodiment allows the copper material 200 to be bonded with sufficient strength to the surface of the ceramic substrate 100 without using silver. Therefore, in this bonded substrate 1, an increase in cost due to silver is suppressed, and migration due to a chemical reaction between silver and other substances present in the surroundings does not occur.

DESCRIPTION OF SYMBOLS 1... Joining substrate 2... Structure 10... First layer 20... Second layer 30... Third layer 100... Ceramic substrate 200... Copper material 300... Joining layer 400... Titanium material 500... Jig, 600...Furnace.

Claims (2)

A bonded substrate in which a copper material is bonded without using silver to the surface of a ceramic substrate made of a material containing nitrogen (N),
As bonding layers formed between the ceramic substrate and the copper material, a first layer containing titanium (Ti) as a main component, a second layer containing copper (Cu) contained in the copper material as a main component, and a third layer, in which a compound of titanium (Ti) and some components contained in the ceramic substrate accounts for 50% by weight or more of the total components of the layer, is formed by removing the copper from the ceramic substrate. The first layer to the third layer are laminated in order toward the material,
The ceramic substrate is a substrate made of silicon nitride (Si ₃ N ₄ ),
In the third layer, a compound of a component made of silicon (Si) and a component made of titanium (Ti) accounts for 50% by weight or more of the whole ,
When the thickness of the first layer is t1, the maximum thickness of the second layer is t2, and the thickness of the third layer is t3, the bonding layer is the third layer and other layers. is formed so that the ratio of (t3/(t1+t2)) is less than 7,
bonding substrate. The second layer is formed with a maximum thickness of 0.1 μm or more,
The bonded substrate according to claim 1.

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