JP2005186211A - Method for cutting substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting method capable of reducing the breaking occurring at the machining end part while suppressing a grinding wheel abrasion amount during cutting when a substrate made of an aluminum nitride sintered body is cut with a cutting grinding wheel. <P>SOLUTION: When the substrate made of the aluminum nitride sintered body is cut by a rotating grinding wheel, the substrate is cut by the rotating grinding wheel using diamond abrasive grains having an average grain size (X;μm) satisfying the range expressed by formula (1): 2d≤x≤150/d to the average crystal grain size (d;μm) of the aluminum nitride sintered body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel method for cutting a substrate made of an aluminum nitride sintered body.

  Ceramic materials represented by aluminum nitride, alumina, boron nitride and the like are widely used because they have excellent characteristics such as electrical characteristics, optical characteristics, and thermal characteristics. Among these ceramic materials, aluminum nitride, in particular, has not only thermal conductivity, but also has excellent properties in terms of insulation, dielectric properties, and thermal expansion characteristics, so it has rapidly spread as a highly functional heat dissipation substrate for semiconductor mounting. It's getting on. Such a heat dissipation substrate is usually manufactured by the following method.

  The substrate made of the aluminum nitride sintered body is finished to a certain surface roughness by grinding or polishing the surface of the sintered substrate, and Ti, Cr, Ni—Cr, TaN, Al, Mo, W, W are formed on the surface. , Zr, etc., a second thin film layer, such as Ni, Pt, and a third thin film layer, such as Co, Cu, Au, Ag, and Pd, are generally formed in this order. After the metal thin film layer is formed on the surface in this way, it is patterned as necessary, then cut and divided to finish the size and shape of the final product, and an electronic device (for example, a laser diode) is formed on the metal thin film layer. Mounted using thin film solder.

  In the cutting of the substrate, as the electronic elements are miniaturized and densified, the processing accuracy has been required to be significantly improved in recent years.

  Conventionally, a rotary grinding wheel is generally used for cutting a substrate made of an aluminum nitride sintered body. Various improvements on the cutting apparatus using the rotary grinding wheel have been proposed for cutting a workpiece with high accuracy (see Patent Documents 1 to 3).

Japanese Patent No. 3132114 JP-A-4-13552 Japanese Patent Laid-Open No. 10-64853

  However, when cutting hard materials such as aluminum nitride sintered bodies, for example, when cutting a large number of products by cutting into blocks or wafers of a certain size, or when performing a number of grooving, a rotating grinding wheel is used. However, the high-accuracy cutting has not been studied sufficiently.

  That is, since the substrate made of the aluminum nitride sintered body is a relatively fragile member, when processing is performed on the substrate, chipping occurs at the processing end portion, which causes a problem that quality deteriorates. In recent years, the position accuracy at the time of cutting has become higher, and the distance between the cutting end and the mounting position of the electronic element has become closer, so it is necessary to make the chip as small as possible to prevent quality deterioration. The

  On the other hand, since a substrate made of an aluminum nitride sintered body is also a relatively hard material, wear of the grinding wheel is great, which adversely affects the economy.

  These tendencies vary depending on the type of aluminum nitride sintered body to be used, and there is a difference in the degree of chipping and the amount of wear on the grindstone.

  The present inventors have intensively studied to solve the above problems. As a result, when a polycrystalline material such as an aluminum nitride sintered body is cut with a rotating grinding wheel, the width of the processed end chip is equal to the average crystal grain size of the aluminum nitride sintered body and the average grain size of the abrasive grains of the grinding wheel. It has been found that the wear amount of the grinding wheel is proportional to the product, and is proportional to the quotient of the average crystal grain size of the polycrystalline material and the average grain size of the abrasive grains of the grinding wheel.

  Based on the above knowledge, by setting the average grain size of the grinding stone to a specific range based on the average crystal grain size of the aluminum nitride sintered body to be cut, it is possible to reduce the wear of the grinding wheel while suppressing grinding wheel wear during cutting. The present inventors have completed a cutting method capable of obtaining a small cut surface and submitted the present invention.

  That is, according to the present invention, when a substrate made of an aluminum nitride sintered body is cut with a rotary grinding grindstone, the substrate is compared with the following (1) with respect to the average crystal grain size (d; μm) of the aluminum nitride sintered body. The substrate is cut by a rotating grinding wheel using diamond abrasive grains having an average particle diameter (x; μm) satisfying the range represented by the formula (1).

    2d ≦ x ≦ 150 / d (1)

  The substrate cutting method of the present invention employs a range of the average particle size of the abrasive grains of the cutting grindstone from the average crystal particle size of the substrate to be cut in the cutting of the substrate made of the aluminum nitride sintered body, The effect that the chip | tip which generate | occur | produces in a process edge part can be made small is suppressed, suppressing the grinding stone wear amount at the time of a cutting | disconnection.

  Therefore, the substrate made of an aluminum nitride sintered body can be cut economically and precisely.

  In the cutting method of the present invention, known substrates are used without particular limitation as the substrate made of the aluminum nitride sintered body. In particular, the substrate for the crystal grain size constituting the sintered body is about 1 to 8 μm. The cutting method of the invention is particularly effective, and those having such a crystal grain size are preferable because they can increase the accuracy of the substrate surface. The thickness of the substrate is preferably 50 μm to 5 cm, particularly preferably 100 μm to 2 cm, from the viewpoint of easy processing.

  The cutting method of the present invention can be applied in any state as long as it is a mode for a substrate made of an aluminum nitride sintered body.

  For example, an unprocessed substrate, a substrate subjected to various honing processing, lapping processing, mirror processing, etc., a substrate for mounting a semiconductor element, metallized on the substrate surface by vapor deposition, sputtering, chemical vapor deposition (CVD), etc. Examples thereof include a substrate on which a layer is formed.

  As the rotary cutting grindstone used for the cutting of the present invention, known ones are used without particular limitation, but those using a grinding grindstone using diamond abrasive grains are suitable. The diamond abrasive is a grinding wheel to which diamond abrasive is fixed using a binder. Natural or synthetic industrial diamond powder is used for the diamond abrasive grains, and the binder may be any method such as resin bond, metal resin bond, metal bond, vitrified bond, electrodeposition bond, and electroformed metal bond. Moreover, the whole grinding wheel may be comprised with the abrasive grain and the binder, and the part which does not relate to a cutting | disconnection may be comprised with other materials, such as a metal.

  The outer diameter, thickness, etc. of the rotary grinding wheel used in the present invention are not particularly limited and may be appropriately determined according to the substrate to be cut, but the thickness of the grinding wheel is determined by the meandering of the cutting groove, the amount of grinding wheel wear. It is preferable that the thickness be as thin as possible within a range where no adverse effects such as increase occur.

  Further, the shape of the tip of a general grinding wheel is a square shape, but it may be R or tapered.

  The average grain size (x; μm) of the abrasive grains in the rotary grinding wheel used in the present invention satisfies the condition of 2d ≦ x ≦ 150 / d (d: average crystal grain size [μm] of the aluminum nitride sintered body). Must be met.

  That is, when x exceeds 150 / d, the width of the chip generated at the processed end portion of the substrate made of the aluminum nitride sintered body is increased, and when x is smaller than 2d, the processed end of the substrate is Although chipping can be prevented, wear of the grinding wheel is increased, and the object of the present invention cannot be achieved.

  A particularly preferable range for the average grain size (x; μm) of the abrasive grains in the rotary grinding wheel is 3d ≦ x ≦ 110 / d.

  The method for fixing the substrate at the time of cutting in the present invention is not particularly limited, and a known method can be used without limitation. For example, vacuum suction, sticking with UV tape, sticking with solid wax, sticking with an adhesive, etc. are applicable, and these may be used in combination. Moreover, what is marketed can be used conveniently for the grinding machine which cut | disconnects.

  A known cutting method can be used without limitation in the present invention. For example, up cut, down cut, creep feed grinding, high speed stroke grinding and the like can be mentioned.

  Moreover, although the grindstone rotation speed should just be 5000 rpm or more, Preferably it is 20000 rpm or more. The upper limit of the rotational speed is not particularly limited, but is about 100,000 rpm, particularly about 60000 rpm.

  The substrate feed rate may be 300 mm / s or less, but is preferably 30 mm / s or less. There are no restrictions due to other processing conditions.

  In order to describe the present invention more specifically, examples and comparative examples will be described below, but the present invention is not limited to these examples.

Examples 1-6
An aluminum nitride sintered body substrate (50.8 mm × 50.8 mm × 0.3 mm) subjected to mirror finishing with an average crystal grain size of 3.3 μm and 4.4 μm has an average grain size of 12 μm (manufactured by Disco Corporation, B1A803SD1200N50M51, 52D × 0.1T × 40H), 15 μm (Disco, B1A803SD800N50M51, 52D × 0.1T × 40H), 25 μm (Disco, B1A803SD600N50M51, 52D × 0.1T × 40H) Using a cutting machine (DAD522, manufactured by Disco Corporation), cutting was performed by down-cutting 100 times (cutting distance 5080 mm) under the conditions of a grinding wheel rotational speed of 23000 rpm and a feed rate of 6 mm / s.

  The aluminum nitride sintered body substrate was attached to a UV sheet (UDV-100A) and vacuum-adsorbed and fixed with a porous chuck. In order to completely cut the substrate, the UV sheet was cut by 50 μm. The amount of decrease in the radius of the grindstone before and after cutting was defined as the amount of wear of the grindstone, and measured with a cutting machine setup function. Observe the processed end after cutting with a 200x measuring microscope, measure the maximum chip width of the cut end within one cut (50.8 mm), and perform this for all cuts. It was set as the processing end part chip width. In the embodiment, the machining end chip width is small and the grinding wheel wear amount is also small.

Comparative Examples 1-4
An aluminum nitride sintered body substrate (50.8 mm × 50.8 mm × 0.3 mm) subjected to mirror finishing with an average crystal grain size of 3.3 μm, 4.4 μm, and 6.7 μm has an average grain size of 12 μm ( Disco, B1A803SD1200N50M51, 52D × 0.1T × 40H), 15 μm (Disco, B1A803SD800N50M51, 52D × 0.1T × 40H), 25 μm (Disco, B1A803SD600N50M51, 52D × 0.1T × 40H), 35 μm Using a grinding wheel (manufactured by Disco Corporation, B1A803SD400N50M51, 52D × 0.1T × 40H), cutting, grinding wheel wear amount, and processing edge chip width were measured in the same manner as in the examples.

Claims (1)

When a substrate made of an aluminum nitride sintered body is cut with a rotating grinding wheel, the substrate is in a range represented by the following formula (1) with respect to the average crystal grain size (d; μm) of the aluminum nitride sintered body. A method for cutting a substrate, comprising cutting with a rotating grinding wheel using diamond abrasive grains having an average particle size (x; μm) satisfying
2d ≦ x ≦ 150 / d (1)