JPH05218662A - Ceramic board and machining method therefor - Google Patents

Abstract

PURPOSE:To obtain a ceramic board in which its surface can be accurately flattened and finer wiring can be formed by laying substances having different elastic moduli on a center and a periphery of a clamping jig of the board and machining the board in a protruding or recess shape. CONSTITUTION:A ceramic thick film multilayer board 3 is formed with a circuit of metal conductors 1 in ceramics. At the time of machining, the board 3 is fixed by a clamping jig 13 by vacuum suction, wax fixing, etc. In the case of machining, a cup-shaped super-abrasive grindstone 12 is rotated, the board 3 is rotated while supplying machining solution 17 to be machined. In this case, a compression residual stress is generated on the surface of the board 3. When the board 3 is removed from the jig 13, it is opened to become a protruding shape. Then, elastic substances having different elastic moduli are laid on an outer periphery and a center of the jig 13, or piezoelectric elements 15 are contained in the jig 13. The conduction is controlled to form a protrusion or a recess, thereby obtaining an accuracy of zero warpage when the board 3 is removed from the jig 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramics module substrate in a large-sized computer and its manufacturing method,
In particular, a process for forming a thin film on a thick film substrate made of ceramics with improved packaging density by plating, CVD, spin coating, etc., and flattening the ceramics substrate surface with high precision when manufacturing a thick film / thin film hybrid substrate. Concerning the law.

[0002]

2. Description of the Related Art Conventionally, a ceramic thick film multilayer substrate has been used as a module substrate of a large-scale computer, but the surface should not be processed as described in Nikkei Electronics (1990, 12, 10). Instead, it was used as it was baked, and an LSI chip was connected thereto via a small chip carrier.

[0003]

Along with the speeding up of arithmetic processing of large-scale computers, the packaging density has also improved significantly.
In a thick film substrate, it is difficult to make fine wiring, and the wiring length becomes long, the substrate area becomes large, and the calculation speed is delayed.
Therefore, a thick film substrate is also used in the form of being laminated in multiple layers, but if the number of layers in the thick film increases, the wiring distance becomes longer and the processing speed becomes slower, so that it is necessary to make part of the film thinner.

The process at this time is as follows. Figure 2
Shows the whole structure.

A large number of ceramic thick films 2 each having a metal conductor 1 patterned therein are stacked and fired to form a ceramic thick film multilayer substrate 3.

Next, a plating base film 4 is formed on the surface of the ceramic thick film multilayer substrate 3, and a plating resist 5 is formed.
After patterning the resist, copper 6 is electroplated, the resist 5 is peeled off, the plating base film 4 is removed, and then a polyimide insulating film 7 is formed and the surface is flattened to form a matching layer 8.

Next, a wiring made of copper and a via stud 9 are formed on the matching layer 8 by the same procedure, and a polyimide insulating film 7 is formed to flatten the surface. This is repeated for the required number of layers to form a thick film / thin film hybrid substrate.

The ceramic thick-film multilayer substrate 3 fired here has a large warp in a size of 200 mm square, and the warp amount of the substrate increases each time the layers are stacked in a thin film process which is a post process, so the warp amount is as small as possible. Is desired.
Further, the amount of warpage of the substrate surface must be consistently within the depth of focus of the exposure apparatus from the beginning to the end of the process. The allowable depth of focus for forming a copper-polyimide thin film multilayer substrate having a wiring thickness of 20 μm and a total of 15 wiring layers is 3
It is 0 μm. Therefore, as a target specification of the warp amount of the surface of the ceramic thick film substrate, it is necessary to set the total warp to 2 μm or less. Since ceramics cannot be processed with ordinary tools, the surface is flattened by grinding with a diamond grindstone, but there is a problem that a large area substrate of 200 mm square tends to warp even when processed, and wiring inside The metal surface is the same as the ceramic surface because a step difference between the ceramic and the metal occurs because of the inclusion of a metal conductor. There was a problem that it had to be lower than that.

[0009]

In order to achieve the above object, a ceramic substrate processing method according to the present invention comprises a method for preferentially processing a metal conductor portion using a cup-shaped diamond grindstone, and a ceramic. The jig is used to fix the substrate while controlling the warpage that occurs during processing.

[0010]

The function of the above technical means is as follows.

In the case of processing with a diamond grindstone, when processing with an ordinary straight type grindstone, the height of the surface of the ceramic becomes lower than the set cutting height of the grindstone because the ceramic portion brittlely fractures. The conductor part projects beyond the ceramic surface. When processing with a cup-shaped diamond grindstone, the ceramic substrate comes into surface contact with the diamond and stone, and it becomes closer to the abrasive chip removal mechanism, so the soft metal conductor is preferentially processed,
As shown in FIG. 3, the surface of the metal conductor portion 1 is lower than the surface of the ceramic 3. However, when processing with a cup-shaped diamond grindstone on a normal vertical grinding machine, the contact time with the grindstone is different between the central part and the peripheral part of the substrate, the central part has a longer contact time, Therefore, the entire substrate has a concave shape with a depressed central portion. Especially, since the center is always in contact with the grindstone, a clear dent may occur. Also, since the substrate has a square shape, the contact area between the substrate and the grindstone changes instantaneously,
When the contact area is maximum, the processing force is also maximized and the load on the grindstone is large. Therefore, the relief of the grindstone at this time is also maximal and the machining amount is small. As a result, the central portion also has a concave shape.

On the other hand, when the surface of the ceramic substrate is processed with a grindstone, a compressive residual stress is generated on the processed surface, and when the substrate is removed from the fixing jig, bending deformation occurs and the shape becomes slightly convex.

The residual stress greatly depends on the processing conditions and the thickness of the substrate, and an extremely flat surface can be obtained by controlling the dent amount in advance in consideration of the warp amount due to the residual stress.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a schematic configuration diagram of a ceramic substrate processing method according to an embodiment of the present invention.

In FIG. 1, 11 is a grindstone spindle of a grinder (not shown), 12 is a superabrasive grindstone attached to the grindstone spindle 11, and this superabrasive grindstone 12 is a metal base 12b. And an abrasive grain 12c made of a hard material such as diamond on the end surface of the base metal 12b, a resin such as phenol,
It is a cup-shaped rotating body made of a metal such as copper, or an abrasive grain layer 12a integrally formed by being contained in an inorganic substance.

Reference numeral 3 is a ceramic thick film multilayer substrate to be processed, and a circuit is formed by the metal conductor 1 in ceramics. Reference numeral 13 is a jig for fixing the ceramic substrate, and the ceramic substrate 3 is fixed by vacuum suction or wax fixing. A piezoelectric element 15 is inserted inside the fixing jig 13. The fixing jig 13 is fixed to the work table 16, and the work table 16 is provided.
Rotate with.

The operation of flattening the ceramic substrate with high precision by the processing method thus constructed will be described.

When the cup-shaped superabrasive grindstone 12 is rotated and the ceramic thick film substrate 3 is also rotated while supplying the machining liquid 17, the ceramic substrate 3 and the superabrasive grindstone 12 are brought into surface contact with each other, and are polished. Since it is closer to the chip removing mechanism, the soft metal conductor portion 1 is preferentially processed, and the surface of the metal conductor portion 1 becomes lower than the surface of the ceramic 3 as shown in FIG. In order to prevent the ceramic substrate 3 from being left unprocessed, the rotation center of the ceramic substrate 3 must be within the locus of the abrasive grain layer 12a of the superabrasive grain grindstone 12, and the center portion and the outer peripheral portion of the ceramic substrate 3 need to be separated. ,
Since the contact time with the superabrasive grindstone 12 is long, the amount of processing of the outer peripheral portion where the contact time is short is small. Then, since the center of the substrate is always in contact with the grindstone, the processing amount is large and the substrate is in a depressed state.

Looking at the contact area with the grindstone 12, the maximum is when the corner of the ceramic substrate 3 enters the locus of the abrasive grain layer 12a, and at this time, the processing force is also maximal, so the grindstone 12
There is a lot of relief and the amount of processing is small, and the corner portion is high and the center is low. FIG. 4 shows a sectional shape of the ceramic thick film multilayer substrate 3 at this time. It has a concave shape as a whole and has a local dent 18 at its center. The overall depression amount h is expressed as a function of time.

On the other hand, when the ceramic thick film multilayer substrate 3 is ground, a compressive residual stress is generated on the substrate surface, and when the ceramic thick film multilayer substrate 3 is removed from the fixing jig 13, it is released to form a convex shape. I will end up. The shape at this time is y =
It can be approximated as −ax ² + b, and the value of the warp amount b largely depends on the plate thickness and the cutting speed.

Since the thickness of the ceramic substrate 3 is constant, the warp amount b can be controlled at the cutting speed.

Now, when the piezoelectric element 15 incorporated in the fixing jig 13 is changed to be convex or concave by the difference between the concave amount h and the warp amount b, the ceramic substrate 3 is fixed to the fixing jig 13.
When it is removed from, it is possible to obtain an accuracy of warpage of 0.

FIG. 5 shows a second embodiment of the present invention. On the upper surface of the fixing jig 13, elastic members 14a and 14b having different elastic moduli at the outer peripheral portion and the central portion are laid, and the outer peripheral portion 14a. When the central portion 14b is hard and the central portion 14b is soft, the amount of processing is small because the escape of the substrate at the time of processing the central portion is large, and it is possible to obtain a surface with few dents in the central portion. When the amount of change due to the residual stress during processing is small, this makes it possible to obtain a flat surface.

By the above processing, it is possible to obtain a ceramic thick film substrate in which the metal conductor portion does not protrude from the ceramic surface and the warp is extremely small, and the next plating or thin film process can be performed.

[0026]

According to the present invention, the surface of the ceramic substrate can be flattened with high accuracy, the warp is 2 μm or less, and the surface roughness is 2.
A ceramic substrate of μm or less can be obtained, the flattening work by glazing of low melting point glass etc. is reduced, and fine wiring can be performed by plating or thin film coating on the upper surface and high performance thick film / thin film hybrid A substrate is obtained.

Further, since the level difference between the ceramic / metal conductor portion on the surface of the substrate is small and the surface of the metal conductor portion is lower by several nm, there is an effect that defects during plating can be reduced. It can also be applied to the surface treatment of materials and contributes to the improvement of economic efficiency.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a structural diagram of a thick film / thin film mixed substrate formed according to the present invention.

FIG. 3 is a cross-sectional view of a ceramic substrate when processed with a cup-shaped diamond grindstone.

FIG. 4 is an enlarged cross-sectional view of the surface of the ceramic substrate when processed with a cup-shaped diamond grindstone.

FIG. 5 is a sectional view of the second embodiment of the present invention.

[Explanation of Codes] 1 ... Metal conductor part, 3 ... Ceramic thick film multilayer substrate, 12 ...
Superabrasive grindstone, 13 ... Fixing jig, 15 ... Piezoelectric element.

Claims (4)

[Claims] 1. A method of processing a ceramic substrate, comprising:
A method for processing a ceramic substrate, characterized by cutting an object having a different elastic modulus between the center and the periphery of a fixing jig of the substrate to process the ceramic substrate into a convex or concave shape. 2. In the above processing method, a piezoelectric element is arranged instead of an object having a different elastic modulus, and the warp of the substrate is controlled.
A method of processing a ceramic substrate, which is characterized in that it is processed while being processed. 3. The processing method according to claim 1, wherein the metal conductor portion in the substrate is 0.2 μm lower than the ceramic surface, the surface roughness of the substrate surface is 2 μm or less, and the warpage is 2 μm or less. Characteristic ceramics substrate. 4. The surface of the ceramic substrate according to claim 1,
Thick film / thin film hybrid ceramic substrate characterized by forming a fine thin film circuit by plating or thin film coating