JPS6012747A - Heat sink for electronic device - Google Patents

Abstract

PURPOSE:To obtain the heat sink excellent in heat dissipating characteristic at low cost by a method wherein an artificial synthetic Ib type diamond crystal having nitrogen content at 5-100ppm is used as the material of the heat sink for a device, and is processed so that the cystal area having the maximum area becomes a plane (110). CONSTITUTION:In manufacturing the titled heat sink the diamond cystal having nitrogen content at 5-100ppm is used. At this time, an unprocessed crystal grown surface is left on at least one surface, and the crystal surface at the part having the maximum area of the processed crystal surface is made as the plane (110). In such a manner, the heat sink excellent in heat dissipating characteristic is obtained at low cost by the use of a diamond having a high thermal conductivity and easy to be processed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field Diamond, as is known, is a material with the best thermal conductivity and has a wide range of industrial uses.

However, in the case of natural rough diamonds, the thermal conductivity varies significantly depending on the nitrogen content. The thermal conductivity is smaller when there is a large amount of iron contained, and the value is 24W/cIyIL~6W at room temperature depending on the contained silicon device.
/'(:tm, degree varies.Among these, the containing titanium equipment selects diamonds with IPPM or less, and lla type (
The one with even higher nitrogen content is called type Ia. ). This lla type diamond exhibits a high thermal conductivity of 20W/J or more, and can be used as a heat sink for heat dissipation in electronic devices such as semiconductor lasers, diodes, and microwave oscillation elements that generate high heat. It is used. The development of these fields has been remarkable in recent years, and the demand for diamond heat sinks is rapidly increasing. The present invention relates to a diamond heat sink used in this electronics device.

(b) Prior Art and Problems However, naturally occurring type 11a gouisemondo is produced in small quantities and is extremely expensive, so high reliability of device performance and long life of the device are required. It is often limited to heat sinks for communication semiconductor lasers or microwave diodes. In addition, even with the same Ila type diamond rough, the thermal conductivity changes depending on the nitrogen content, so it has the disadvantage of lacking stability. It is also well known that diamond is the hardest substance. For this reason, processing is extremely difficult. Generally, when processing diamonds, a paste made of rapeseed oil and diamond powder is applied to a cast metal disk, the disk is rotated at high speed, and a diamond is pressed onto it to polish it. method is taken. In this case, diamond has significantly different wear characteristics depending on its crystal plane. (100) plane,
Table 1 shows the wear characteristics of (111) and (110) surfaces.
Shown below.

Table 1 Note) Wear amount is the maximum amount of wear on each surface. Polished in a direction that is easy to scratch.

Therefore, if you polish the (110) plane, it will cut well, but if you accidentally polish the (111) plane, only the cast disc will be ground, and the diamond will be in a state where it is almost impossible to cut it. For this reason, correctly determining the surface orientation of rough diamonds is an essential condition for processing diamonds. Most natural rough stones are composed of dodecahedrons consisting of 110 faces, or octahedrons consisting of (i, g, and g faces), but in many cases the edges of the boundaries between the faces and 1ai are fused.
Finding the plane direction requires skill and is often error-prone. or,
Since most of the surfaces are curved, a considerable portion of the diamond must be polished. This requires processing costs, and because the diamond surface is used as an electrode for electronics devices, a gold coating must be applied to the surface. The technology involved is difficult, and sufficient surface strength cannot be obtained over all the heat sinks, resulting in poor yields. The surface of diamond is highly activated and has an extremely large amount of oxygen attached to it. For this reason, if gold is simply vapor-deposited, the adhesion strength with diamond is low, and devices, lead wires, etc. cannot be bonded together.

Usually, a metal that easily reacts with oxygen, such as Ti or Cr, is first coated using a method such as ion blasting or sputtering, and then gold is coated on top using the same method or vapor deposition method, and used as a heat sink. .

In this case, the surface treatment and coating conditions when coating Ti, Cr, etc. are too hot, and sufficient adhesion strength cannot be obtained between the diamond and the coating film, and when the lead wire is bonded, the coating film peels off. There is something to do.

(C) Structure of the Invention The present invention solves the above-mentioned problems by using artificially synthesized diamond, which has stable high thermal conductivity.
The present invention also provides a diamond heat sink that is easy to process. First, we will explain the identification of a diamond rough device whose thermal conductivity is within a stable and high range. Artificially synthesized diamonds used in heat sinks are mainly produced using the film growth method used for abrasive grain synthesis and the temperature difference method. We will discuss the case of using an artificial diamond rough. The nitrogen content was determined by varying the growth rate from 1 m g/b to 3.5 mg/h.
It was varied from 0 to 150 PPM. Initially, the means to control the growth rate was to change the temperature difference by changing the distance between the carbon and diamond seed crystal materials in Figure 1 (by changing the length of the solvent), but the reproducibility of the growth rate was was not very good.

Therefore, in the present invention, as shown in Fig. 2, a high melting point metal disk such as MO with good thermal conductivity is placed under the diamond seed crystal material, and the thickness of the disk is changed so that the heat dissipates downward. By changing the amount of heat and changing the temperature difference between the diamond seed crystal material and the carbon source to change the growth rate, the variation in growth rate became smaller. The nitrogen content is measured using an infrared absorption measuring device at 11' of the rough diamond.
30CI4-1 was identified to accurately measure the absorption coefficient.

FIG. 5 shows the relationship between the absorption coefficient and the nitrogen content.

Further, FIG. 4 shows the relationship between the growth rate of the rough diamond synthesized by the above method and the nitrogen content device. Although the figure uses a nickel solvent, the same results were obtained with other solvents. As a result, a type Ib diamond rough containing 110PP to 150PPM of nitrogen was obtained. When the thermal conductivity of these diamonds was measured, the fifth
The results shown in the figure were obtained. As a result, 10PPM
Within the range of ~1100PP, the thermal conductivity is almost constant and exhibits a high value, but when it reaches 150PPM, the thermal conductivity begins to exhibit a low value. From this, it can be seen that the chit device is 10 to 10
It can be seen that the heat sink made from synthetic diamond within the range of DI"PM has high thermal conductivity and is a good heat sink for electronic devices with little variation.On the other hand, synthetic diamond has nitrogen It aggregates and precipitates on specific crystal faces in units of several hundred angstroms.

This is based on the difference in the crystal growth environment.

However, since the type Ib synthetic diamond of the present invention contains nitrogen as a solid solution, the decrease in thermal conductivity is small. The problem with No. 2 and 1 is that when processing a diamond heat sink, it has the above-mentioned drawbacks compared to natural stone (Ila type).

■Glass with good surface orientation, polished part (surface that can be polished well)
may be mistaken.

■The diamond surface has many curved surfaces and requires a lot of machining cost and time.

In the present invention, by using artificially synthesized diamond with a clear crystal grain size of 1/77 (see Fig. 6 d), the diamond crystal plane orientation can be easily 114-°rIJ, and the polished surface can be polished by 1° (no rounding). Since the crystal faces are flat, it is possible to use the grown crystal faces as they are. Figure 7 shows some examples of using the grown crystal faces as they are.Diamond A heat sink must be coated with a metal such as gold on top of this. Normally, crystal planes that have grown to a certain size often have growth steps remaining. After all, large steps remain during coating. To eliminate this large step, adding silicon to the solvent or carbon source will give a smooth crystal surface that is almost the same as polished surfaces. During ion blating and sputtering of Ti, Cr, etc., the strength of the coating film increases, probably due to the creation of silicides of Ti and silicon.However, the amount of silicon contained in synthetic diamond is 1ooppM.
The following are desirable.

2) Effects of the invention As in the two series of the present invention, the nitrogen content is 10 to 100.
By using PI'M's synthetic diamond rough diamond type, a high-quality heat sink for electronic devices with high thermal conductivity (equivalent to natural 11a) and little variation can be obtained. In addition, we use artificially synthesized rough diamonds, which are cheaper than natural 112-type diamonds, and are easier to process and require less processing cost than natural rough diamonds.Moreover, we can use a part of the crystal face as it is without any processing, so it can be used as part of a heat sink. The present invention can provide an inexpensive heat sink for electronic devices. It has the same effect as above.

Examples Example 1 A 0,4+j synthetic diamond consisting of hex-octahedrons was produced by the temperature difference method as shown in FIG.

The solvent used was iron and nickel alloy, and the synthesis temperature was 1450
°C1 pressure was 5.6 GP synthesis time was 48 hours. Infrared spectroscopy 2: (Nitrogen content f amount measured with
It was PPM. Using this rough stone, 0.
It was cut into slices with a thickness of 8 mm. Polish both sides of this sliced diamond to a thickness of 0.5 [10
0) With the surface facing the side, use a laser to cut 1mm x
It was cut to 1ynm. Furthermore, one side of the cut diamond was removed at a 45° angle, treated with acid, and then coated with T+ and Au using ion blating.

After performing a performance test by attaching a semiconductor laser to -1- of the completed heatsink, I installed it on a natural +1A type heatsink (the same N/8 ratio as in the case of a single digit was obtained, and the laser life was also the same). Ta.

[Brief explanation of the drawing]

In the figure, 1 is a diamond seed crystal, 2 is a solvent, 6 is a carbon source,
4 is a pressure medium, and 5 is a heating heater. 6 is a pressure medium, and 7 is a disk made of Mo or the like. FIG. 6 shows the relationship between the absorption coefficient and nitrogen concentration for type Ib and type Ia, with the horizontal axis representing the nitrogen concentration and the vertical axis representing the absorption coefficient. FIG. 4 shows the relationship between nitrogen concentration and growth rate. Fifth
The figure shows ■a (natural) and Ib1) for each temperature (horizontal axis)
The inside shows the thermal conductivity of I and Ia (natural) type diamonds, which show the nitrogen content. FIG. 6 shows the shape of a general artificially synthesized diamond single crystal. FIG. 7 shows an example in which when a heat sink is produced from an artificially synthesized diamond rough, the crystal growth surface is used as the surface of the heat sink. Part 1 (2) Figure 2 Procedural Amendment (Method) 1. Display of the case 1982 Patent Application No. 120475 2, Name of the invention Heat sink for electronic devices 3, Person making the amendment Relationship to the case Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (213)
President of Sumitomo Electric Industries, Ltd. Tetsube 4, Agent address: 6, Sumitomo Electric Industries, Ltd., IBa, 1-chome, Shimaya, Konohana-ku, Osaka, Column 7 for brief explanation of drawings in the specification subject to amendment, Amendment At the bottom of the detailed description of contents, page 11, line 1, 14, ``Brief explanation of the drawings'', it says ``Figure 1 shows a conventional diamond synthesis method.
No. 2181 inserts "Synthesis method according to the present invention". Procedural amendment 1. Display of the case 1982 Patent Application No. 120475 2, Name of the invention Heat sink for electronic devices 3, Person making the amendment 4, Representative 6, Number of inventions increased by the amendment 7, Application subject to the amendment and in the specification, the title of the invention column, the claims column, and the drawings. 8. Contents of the amendment (1) The name of the invention in the application and specification is corrected to "Heat sink for electronic devices and manufacturing method thereof." (2. The scope of the claims is corrected as shown in the attached sheet. (3) The drawing (Figure 5) is corrected as shown in the attached sheet. (4) On page 2, line 17 of the specification, "for communications" is changed to " (5) The condition column in Table 1 on page 3 of the same book is corrected as follows. Table 1 (6) “There is a range” in line 17 of page 5 of the circular. (7) Correct "10 to 150 PPMJ" in the fourth line of page 6 of the same book to "Nitrogen content is 5 to 150 PPMJ." (8) 'Correct the nitrogen content to 5 to 150 PPMJ.' Correct "Identified by" to "Measured by". (9) rlOPPM on page 7, lines 2 to 3,
Correct ~+50PPMJ to [5~+50PPMJ. (10) Same book, same page, line 6 r IOPPM -1100
PP J is corrected as ``5-10100PP. (11) Same book, page 7, line 9 [10-10100PP is corrected as ``5-10100PP. (I2) Same book, page 9, line 9 [I Next, insert the following: ``Another feature of the present invention is that by using artificially synthesized type Ib diamond whose surface orientation is easy to determine, it is possible to easily select the (I0) surface as the processed surface with the largest area. The reason for this is that, as shown in Table 1, the (11G) surface is a surface that can be easily machined, and heat sinks for electronic devices with a large amount of machining are more practical because the machining cost is low.For example: In the heat sink shown in Fig. 7D, the plane portion having the maximum area is the (+10) plane.'' (I3) Ibid. No. 9
Page 11th line r 10- +00PPM J to "5~1
Corrected to 0100PP. Claims: ``(1) I containing an amount of nitrogen of 5 to 1100 PP
A heat sink for electronic devices characterized by using b-type diamond crystal. (2) Containing sulfur nitrogen m h<, 5-1100PP 1
'A method for manufacturing a heat sink for electronic devices, characterized by processing a certain type Ib diamond crystal with a specific crystal plane. (3) The method for manufacturing a heat sink for an electronic device according to claim 0, wherein an unprocessed crystal growth surface is left on at least one surface. (4) The method for manufacturing a heat sink for an electronic device according to claim 0, wherein the crystal plane having the largest area among the processed crystal planes is the (11G) plane. ”

Claims (1)

[Claims] (1) Ib containing nitrogen amount is -~1100PP
τQ) The heat sink for an electronic device according to claim 1, wherein an unprocessed crystal growth surface is left on at least one surface of the diamond crystal.