JPH11126979A - Multi-layer substrate and its base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high adhesion to an insulating layer of organic high polymer and to prevent the insulating layer from blistering or peeling by specifying a surface roughness of the surface of a ceramics substrate. SOLUTION: With a surface roughness of a ceramics substrate 2 equal to 0.25 μmRa or above, the rough of a surface is appropriately coarse, thus adhesion to an insulating layer 3 of organic high polymer is raised. So, at manufacturing, the organic high polymer layer 3 is prevented from 'blistering' or 'peeling'. Further, when a multiple multi-layer substrates 1 are cut out of a base material, the organic high polymer layer is hard to peel off, preventing occurrence of a defective article. Although the adhesion is higher when a surface roughness is higher than a specified value, which is preferable, such new issue arises as variation in resistance value becomes larger if the surface roughness exceeds 1.0 μmRa. Therefore, the substrate with roughness 1.0 μmRa or less appropriate as variation in resistance value is small. Here, Ra is center line average roughness specified by JIS.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer substrate formed by laminating an insulating layer made of an organic polymer such as polyimide on the surface of a ceramic substrate and used for, for example, an IC substrate and a base material thereof.

[0002]

2. Description of the Related Art Hitherto, as a substrate such as an integrated circuit substrate (IC substrate), there has been known a multilayer substrate formed by laminating an insulating layer made of an organic polymer such as polyimide on the surface of a ceramic substrate.

As a technique relating to this multi-layer substrate, for example, Japanese Patent Application Laid-Open No. 63-148659 discloses that, when polyimide is used as an interlayer insulating layer, the surface of an electrode or wiring metal under the polyimide is excellent in adhesion to the polyimide. Techniques for covering with materials are described. Japanese Utility Model Laid-Open Publication No. 1-11387 discloses a technique of covering an end of a lower polyimide insulating layer until it reaches the upper surface of a ceramic substrate.

[0004]

However, the above-mentioned technique is not always sufficient because the adhesion between the organic polymer layer and the ceramic substrate cannot be directly increased. In other words, conventionally, when an organic polymer layer made of polyimide or the like is laminated on the surface of a ceramic substrate, the adhesion strength is insufficient, and the organic polymer layer is distorted and swelled during manufacturing or the like. However, there was a problem that "peeling" was caused to peel off from the ceramic substrate.

In the case of manufacturing a multi-layer substrate in which a plurality of organic polymer layers are laminated on a ceramic substrate, in order to manufacture many multi-layer substrates at once, a base material of the multi-layer substrate larger than a target size is required. Manufacture and cut it to cut out a large number of multi-layer boards of desired dimensions.
Peeling occurs between the ceramic substrate and the organic polymer layer,
There was a problem that defective products frequently occurred.

Further, when polyimide is used as an organic polymer, a low expansion polyimide may be used for a layer in contact with the ceramic substrate in order to reduce the warpage of the ceramic substrate. However, there is also a problem that the adhesion strength is further reduced because of being rigid and linear.

Accordingly, an object of the present invention is to provide a multilayer substrate having excellent adhesion between a ceramic and an organic polymer and a base material thereof.

[0008]

Means for Solving the Problems According to the first aspect of the present invention, there is provided a multi-layer substrate comprising a ceramic substrate and a plurality of insulating layers made of an organic polymer laminated on a surface of the ceramic substrate. The surface roughness of the surface of the ceramic substrate
The gist of the present invention is a multi-layer substrate characterized by being at least 0.25 μmRa and at most 1.0 μmRa.

That is, the surface roughness of the ceramic substrate is set to 0.2.
When it is 5 μmRa or more, the surface irregularities are appropriately roughened, and the adhesion to an insulating layer made of an organic polymer (hereinafter also referred to as an organic polymer layer) is enhanced. Thereby, "swelling" and "peeling" of the organic polymer layer at the time of manufacturing or the like can be prevented. Also, when many multi-layer substrates are cut from the base material and cut out, the organic polymer layer is hardly peeled off, and the occurrence of defective products can be prevented.

As described above, it is preferable that the surface roughness is higher than a predetermined value because the adhesion is high and the surface roughness is preferably 1.0 μm.
When it exceeds Ra, another problem that the variation of the resistance value becomes large arises. Therefore, those having a resistance of 1.0 μm Ra or less have a small variation in the resistance value and are suitable.

The reason why the resistance value deteriorates is that when the surface roughness increases, the dimensional variation of the electrode layer formed on the surface of the ceramic substrate and the dimensional variation of the resistance layer increase, and the sheet resistance (the ceramic substrate) increases. It is considered that the variation of the resistance value in the resistance layer becomes large as a whole because the resistance of the resistance layer also varies.

Here, Ra is a center line average roughness defined by JIS. Further, as the material of the ceramic substrate, alumina, aluminum nitride, mullite, magnesium, silicon nitride, sintered ceramics such as spinel,
Low-temperature fired materials such as crystallized glass and glass-ceramic composites are exemplified.

According to a second aspect of the present invention, there is provided a multilayer substrate as set forth in the first aspect, wherein the surface roughness of the surface of the ceramic substrate is 0.4 μm Ra or more. In particular, when the surface roughness is 0.4 μm Ra or more, the adhesion is even higher,
This is preferable because the effect obtained by the invention of claim 1 becomes more remarkable.

According to a third aspect of the present invention, there is provided a multilayer substrate according to the first or second aspect, wherein the organic polymer is polyimide. That is, in the present invention, polyimide, which is an organic polymer, can be adopted as the material of the insulating layer.

According to a fourth aspect of the present invention, the insulating layer has an interface polyimide layer made of a normal polyimide having a normal coefficient of thermal expansion in contact with the surface of the ceramic substrate, and a lower thermal expansion laminated on the interface polyimide layer. The multi-layer substrate according to claim 3, further comprising an upper polyimide layer made of a low expansion polyimide having a coefficient.

That is, in the present invention, contrary to the prior art, the interface polyimide layer is formed using normal polyimide having a large coefficient of thermal expansion, and the upper polyimide layer is formed using low expansion polyimide having a small coefficient of thermal expansion. doing. This ordinary polyimide has higher adhesion to the ceramic substrate because the molecular chain is relatively flexible and not linear, as compared with the low expansion polyimide. In addition, the low expansion polyimide has a high resistance to substrate warpage because the molecular chain is rigid and linear.

Therefore, according to the present invention, the adhesion is usually increased by the polyimide, and the warpage is prevented by the low expansion polyimide, so that both the adhesion and the warpage can be realized with high performance. Here, the usual polyimide is
A polyimide having a coefficient of thermal expansion of 30 × 10 ⁻⁶ / ° C. or more, while a low-expansion polyimide usually has a coefficient of thermal expansion smaller than that of polyimide, preferably 20 × 10 ⁻⁶ / ° C. or less. For example, as a normal polyimide, a PIQ (trade name) manufactured by Hitachi Chemical Co., Ltd. having a thermal expansion coefficient of 58 [× 10 ⁻⁶ / ° C.] can be adopted.
PIX-L110SX (trade name) manufactured by Hitachi Chemical Co., Ltd. having a coefficient of thermal expansion of 10 [× 10 ⁻⁶ / ° C.], or having a coefficient of thermal expansion of 2
0 [× 10 ^-6 / ° C] UR-5100FX manufactured by Toray
(Product name) or the like can be adopted.

According to a fifth aspect of the invention, there is provided a multi-layer substrate according to the fourth aspect, wherein the thickness of the interface polyimide layer is 0.1 μm or more and 25 μm or less. That is, when the thickness of the interface polyimide is 0.1 μm or more, there is an advantage that the adhesion between the ceramic and the polyimide layer can be ensured, and when it is 25 μm or less, there is an advantage that the warpage of the substrate can be suppressed small. Therefore, this range is preferable.

According to a sixth aspect of the present invention, there is provided a multilayer substrate as set forth in the fifth aspect, wherein the thickness of the interface polyimide layer is 1 μm or more and 10 μm or less. That is,
If the thickness of the polyimide at the interface is 1 μm or more and 10 μm or less, the advantage described in claim 5 becomes even greater, so this range is more preferable.

According to a seventh aspect of the present invention, there is provided a base material from which a multilayer substrate is cut out, wherein the base material has a configuration similar to that of the multilayer substrate according to any one of the first to sixth aspects. Is the gist. That is, in the present invention, the base material itself is shown, not the multilayer substrate cut out from the base material. Since the base material has a similar configuration to the above-described multilayer substrate, although the dimensions are different, similar effects such as high adhesion and small variation in resistance are exhibited.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples (embodiments) of a multilayer substrate and a base material thereof according to the present invention will be described with reference to the drawings. a) A part of the multilayer substrate 1 according to the present embodiment is cut away and shown in FIG. 1. The multilayer substrate 1 is a substrate on which an integrated circuit (IC) is mounted. Insulating layer 3 composed of layers is laminated.

The ceramic substrate 2 is made of alumina and has a length and width of 20 mm and a thickness of 1.0 mm. On the other hand, the insulating layer 3 includes a 3 μm-thick interface polyimide layer 4 that is directly bonded to the surface of the ceramic substrate 2, and four upper polyimide layers 5 stacked on the interface polyimide layer 4, that is, the interface polyimide layer 4. From the side of the polyimide layer 4, the first polyimide layer 6 having a thickness of 22 μm, the second polyimide layer 7 having a thickness of 25 μm,
It comprises an upper third polyimide layer 8 having a thickness of 25 μm and an upper fourth polyimide layer 9 having a thickness of 25 μm.

Of these, the interface polyimide layer 4 is made of ordinary polyimide having a relatively large coefficient of thermal expansion.
For example, it is composed of a PIQ (trade name) manufactured by Hitachi Chemical Co., Ltd. having a thermal expansion coefficient of 58 [× 10 ⁻⁶ / ° C.]. Also,
Each of the four upper polyimide layers 5 is made of a low-expansion polyimide having a small coefficient of thermal expansion.
[× 10 ⁻⁶ / ° C.] PIX-L11 manufactured by Hitachi Chemical Co., Ltd.
0SX (trade name) or a coefficient of thermal expansion of 20 [× 10 ^-6 /
C]] of UR-5100FX (trade name) manufactured by Toray Industries, Inc.

The surface wiring layer 11 made of, for example, Cr-Ti-Cu-Ni-Au or the Cr-Ti-Cu -Internal wiring layer 1 made of Au
1 ′ is provided, and a via 12 in which holes are filled with, for example, Cu is provided to connect the respective wiring layers 11, 11 ′ in the thickness direction of the substrate.

Therefore, the interface polyimide layer 4 covers the ceramic portion of the surface of the ceramic substrate 2 where the surface wiring layer 11 is not provided, and also covers the surface wiring layer 1.
1 also covers the surface. b) Next, a method for manufacturing the multilayer substrate 1 of the present embodiment will be described.
A description will be given based on FIG.

FIG. 2 schematically shows the manufacturing process of the multilayer substrate 1 (particularly, the vertical direction is larger than the horizontal direction). Here, in order to clarify the configuration of this embodiment. A conventional example (comparative example) will also be described. First, a green sheet is formed by a doctor blade method using a ceramic material such as Al ₂ O ₃ , SiO ₂ , CaO and an organic molding aid.
By firing at a temperature of 0 to 1550 ° C., a ceramic plate 21 which is a plate before cutting the ceramic substrate 2 is manufactured.

The ceramic plate 21 is 110 m in length and width.
It is a plate material made of alumina ceramic having a mx 1.0 mm thickness. As will be described later, a multi-layer substrate base material (base material) 22 is cut into five rows and five rows each to obtain 5 x 5 = 25 total multilayers. The substrate 1 is cut out. Polishing Step Next, the surface of the ceramic plate 21 is polished using a polishing material having a predetermined roughness so as to have a surface roughness within a predetermined range (that is, 0.25 μmRa or more and 1 μmRa or less). Here, the surface roughness was set to 0.27 μmRa by polishing.
Incidentally, in the conventional example, it is 0.02 μmRa.

Step of Forming Interface Polyimide Layer Next, the wiring layer 11 is formed by plating using a photoresist technique on a required portion of the surface of the ceramic plate 21, and then the surface of the ceramic plate 21 and the surface of the wiring layer 11 are formed. Apply the above-mentioned usual polyimide, then dry it,
An interface polyimide layer 4 is formed. In FIG. 2, the wiring layers 11, 11 'and the vias 12 shown in FIG. 1 are omitted.

Next, the above-mentioned low expansion polyimide is applied to the surface of the interface polyimide layer 4 and then dried to form the upper first polyimide layer 6. Thereafter, through holes (not shown) which become vias 12 are formed by photolithography or the like at necessary portions of the interface portion polyimide layer 4 and the upper first polyimide layer 6, that is, portions which can be in contact with the wiring layer 11 on the ceramic plate 21. ).

Next, a wiring layer 11 is formed by plating using a photoresist technique at a necessary portion of the surface of the upper first polyimide layer 6, and a C layer is formed in the through hole.
Fill with u paste. Similarly, the upper second to upper fourth polyimide layers 7 to 9 are formed in the same manner, and the wiring layers 11 and the vias 12 are formed in the respective layers.
To manufacture.

Cutting Step Next, the multi-layer substrate base material 22 is cut into five rows and five columns using a cutter (not shown), and a total of 25 multi-layer substrates 1 are cut.
Cut out. Thus, in this embodiment, the surface roughness of the surface of the ceramic substrate 2 is set to 0.25 μm, such as 0.27 μm Ra.
Since it is at least μmRa, the adhesion strength between the ceramic substrate 2 and the interface polyimide layer 4 is large. Therefore, it is possible to prevent blistering of the insulating layer 3 and, as shown in FIG. 3, to prevent the insulating layer 3 from peeling (as in the comparative example) when cutting the multilayer substrate base material 22.

Further, in this embodiment, since the ordinary polyimide which is not so rigid is used for the interface portion polyimide layer 4, the adhesiveness to the ceramic substrate 2 is excellent also from that point. Further, in the present embodiment, since the rigid low expansion polyimide is used for the upper polyimide layer 5 occupying most of the insulating layer 3, there is an effect that the warpage of the multilayer substrate 1 can be prevented. <Experimental Example> Next, an experimental example performed to confirm the effect of the multilayer substrate of the present embodiment will be described.

Here, the surface roughness (surface roughness) of the surface of the ceramic substrate was changed, and the kind of polyimide constituting the interface polyimide layer and the upper polyimide layer was changed. Then, as shown below, cutter knife evaluation,
Peeling during cutting, the amount of substrate warpage, and resistance variation were measured. The results are shown in Table 1 below.

Evaluation of Cutter Knife A cutter knife was inserted between the ceramic substrate and the polyimide layer at the interface, and it was examined whether or not it was easily peeled. In Table 1, it is shown that the larger the numerical value among 1, 2, 3, 4, and 5, the easier it is to peel off.

Peeling at the time of cutting In the case where 100 multilayer substrates were manufactured by cutting, the number of polyimide layers in which the interface portion polyimide layer was peeled off from the ceramic substrate was shown. The amount of warpage of the substrate The amount of warpage as shown in FIG.

Resistance Variation As shown in FIGS. 4B and 4C, an electrode layer (300 μm × 300 μm × 5 μm in thickness) is formed on a ceramic substrate, and Ta ₃ N is formed between the electrode layers. Length and width 200μ
A resistance layer having a dimension of m was formed, and the resistance value was measured. Then, the degree of variation with respect to the target resistance value (50Ω) was examined.

In the following table, the column of total evaluation indicates that the evaluation becomes higher in the order of ×, Δ, ○, ◎.

[0038]

[Table 1]

Further, a plurality of multilayer substrates were manufactured by changing the thickness of the interface portion polyimide layer, and the adhesion to the ceramic substrate and the amount of warpage of the substrate were confirmed. Table 2 shows the results.

[0040]

[Table 2]

The types A, B and C of the polyimides in Tables 1 and 2 are shown in Table 3 below.

[0042]

[Table 3]

I) As is clear from Table 1, when the surface roughness is 0.25 μm Ra or more, it is preferable that the peeling is small. The resistance variation is smaller as the surface roughness is smaller. In particular, when the surface roughness is 1.0 μmRa or less,
This is preferable because it is within ± 10%.

Therefore, considering the peeling and the resistance variation, it is preferable that the surface roughness is in the range of 0.25 μmRa or more and 1 μmRa or less. When the surface roughness is 0.4 μm Ra or more, the peeling is further reduced, which is more preferable.

Ii) Further, with respect to the warpage of the multilayer substrate, the polyimide layer at the interface and the upper polyimide layer are made of low expansion polyimide A-low expansion polyimide A, low expansion polyimide A-low expansion polyimide A, and usually polyimide C-low. The case of the expanded polyimide A is preferable, but the adhesiveness indicated by the experimental results of the evaluation of the cutter knife and the peeling at the time of cutting is high when the interface portion polyimide layer is usually formed of polyimide.

Therefore, it can be understood that the polyimide having a small warpage and high adhesiveness has a relationship between the polyimide layer at the interface portion and the polyimide layer at the upper layer, which is usually a polyimide C-low expansion polyimide A. Note that even when the interface polyimide layer and the upper polyimide layer have a relationship of low expansion polyimide A-low expansion polyimide A, low expansion polyimide A-low expansion polyimide A, the surface roughness is 0.25 μm Ra or more. 0 μm Ra
Within the following range, there is an effect that the adhesion is high to some extent.

Iii) As apparent from Table 2, the thickness of the polyimide layer at the interface is 0.1 μm or more and 25 μm or more.
In the following cases, it is preferable in that the amount of warpage of the substrate is small while ensuring the adhesion, and the effect is more remarkable particularly when the thickness of the interface polyimide layer is 1 μm or more and 10 μm or less. become.

[0048]

As described above, according to the first aspect of the present invention, the surface roughness of the surface of the ceramic substrate is set to 0.25 μmR.
Since it is not less than a and not more than 1.0 μmRa, the adhesiveness with the insulating layer made of an organic polymer is high, and “swelling” of the insulating layer
And "peeling" can be prevented. In addition, the resistance value is preferably small in variation.

According to the second aspect of the present invention, since the surface roughness of the surface of the ceramic substrate is set to 0.4 μmRa or more, it is preferable to further increase the adhesion. According to the third aspect of the present invention, since the insulating layer is made of polyimide, which is an organic polymer, the insulating layer is excellent in insulation properties and heat resistance.

According to the fourth aspect of the present invention, since the interface polyimide layer is laminated on the surface of the ceramic substrate and the upper polyimide layer is further laminated, the adhesion to the ceramic substrate is high, and the resistance to warpage of the substrate is high. Claim 5
In the invention, the thickness of the interface polyimide layer is 0.1 μm
As described above, since the thickness is 25 μm or less, the adhesion to the ceramic substrate is maintained high, and the warpage of the substrate can be suppressed to a small value.

According to the sixth aspect of the present invention, since the thickness of the interface polyimide layer is not less than 1 μm and not more than 10 μm, the above effect is further enhanced. According to the seventh aspect of the present invention, since the base material from which the multilayer substrate is cut has the same configuration as the multilayer substrate, similar effects such as high adhesion and small variation in resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a multilayer substrate according to an embodiment with a part cut away.

FIG. 2 is an explanatory view showing a method for manufacturing a multilayer substrate according to an embodiment together with a conventional example.

FIG. 3 is an explanatory diagram showing a state of the multilayer substrate after cutting.

FIG. 4 shows an experimental example, (a) is an explanatory diagram showing warpage,
(B) is a plan view showing an experimental example of resistance, and (c) is a cross-sectional view taken along the line II of (b).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Multilayer board 2 ... Ceramic substrate 3 ... Insulating layer 4 ... Interface polyimide layer 5 ... Upper polyimide layer 6 ... Upper first polyimide layer 7 ... Upper second polyimide layer 8 ... Upper third polyimide layer 9 ... Upper fourth polyimide Layer 11: Surface wiring layer 11 ': Internal wiring layer 12: Via 21: Ceramic plate 22: Multilayer substrate base material

Claims (7)

[Claims] 1. A multilayer substrate comprising a ceramic substrate and a plurality of insulating layers made of an organic polymer laminated on the surface thereof, wherein the surface of the ceramic substrate has a surface roughness of 0.25 μmR.
a multilayer substrate having a thickness of not less than a and not more than 1.0 μmRa. 2. The surface roughness of the surface of the ceramic substrate,
2. The multilayer substrate according to claim 1, wherein the thickness is 0.4 μm Ra or more. 3. The multilayer substrate according to claim 1, wherein the organic polymer is polyimide. 4. The insulating layer has an interface polyimide layer made of normal polyimide having a normal thermal expansion coefficient in contact with the surface of the ceramic substrate, and a lower thermal expansion coefficient laminated on the interface polyimide layer. The multilayer substrate according to claim 3, further comprising an upper polyimide layer made of a low-expansion polyimide. 5. The method according to claim 1, wherein the polyimide layer at the interface has a thickness of 0.1.
The multilayer substrate according to claim 4, wherein the thickness is 1 m or more and 25 m or less. 6. The method according to claim 1, wherein the thickness of the interface polyimide layer is 1 μm.
The multilayer substrate according to claim 5, wherein the thickness is not less than m and not more than 10 µm. 7. A base material from which a multilayer substrate is cut out, wherein the base material has a configuration similar to that of the multilayer substrate according to any one of claims 1 to 6.