JP2007081412A - Substrate for submount material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a submount material in which the lifting of a metal circuit layer is small even in the case where heat impact is exerted during an assembly step and in use and heat dissipation property, durability, and reliability are excellent. <P>SOLUTION: In a substrate 2a for a submount material using an aluminum nitride substrate whose thermal conductivity is equal to or more than 170 (W/m K), the longitudinal and transversal lengths of the aluminum nitride substrate is equal to or less than 1 mm and K/t ratio is equal to or more than 700 in the case where the thermal conductivity of the aluminum nitride substrate is K (W/m K) and thickness is t (mm). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a substrate for a submount material for holding and mounting a laser diode or the like, and more particularly to a substrate for a submount material that has less peeling of a metal circuit layer and is excellent in durability and heat dissipation.

  Conventionally, a photodiode is mounted on a submount made of a ceramic substrate and a metal circuit layer in order to receive an optical signal as a surface light and supply it to an external circuit as an electric signal, and the electric signal from the photodiode is transferred to the metal circuit layer. A photodiode sub-assembly is widely used as an optical element that supplies an external circuit via a semiconductor device. Laser diode light-emitting elements using laser diodes that emit surface light instead of photodiodes are also widely used as display parts for home appliances and electronic devices.

  FIG. 2 is a cross-sectional view showing a configuration example of a laser diode light emitting element. In the figure, a laser diode light-emitting element 1 is formed by integrally bonding a laser diode 6 to a submount material 4 composed of a ceramic substrate 2 and a metal circuit layer 3 formed by sputtering, for example, via a solder layer 5. Configured. The laser diode 6, the metal circuit layer 3, and an external circuit (not shown) are electrically connected to each other by a bonding wire (not shown). Further, in order to release the heat generated in the laser diode 6 out of the system via the submount material 4, the lower part of the submount material 4 is formed of copper (Cu) or the like having good thermal conductivity. The heat sinks 7 are joined together.

  Conventionally, as the submount material 4 for the laser diode 6, a sublayer in which a metal circuit layer is formed on a surface of a SiO substrate in which an oxide film is formed on the surface of a plate-like Si plate using a thin film forming technique such as a sputtering method. Mount materials are widely used. Further, a gold (Au) plating layer is formed on the surface of the metal circuit layer in order to improve the electrical conductivity, adhesion or bonding between the metal circuit layer and the laser diode, and Au- In some cases, a solder layer made of Sn alloy or Pb—Sn alloy may be formed. In recent years, an aluminum nitride (AlN) substrate having high thermal conductivity has been widely used as a ceramic substrate constituting a submount material in order to cope with an increase in output of a diode and realize higher heat dissipation characteristics.

  However, in the conventional submount material in which an aluminum nitride (AlN) substrate is used as a ceramic substrate and a metal circuit layer is formed using a sputtering method as in the conventional example, the adhesive strength of the metal circuit layer is low. However, there is a problem that the metal circuit layer is easily peeled off due to heat that repeatedly acts during the assembly process or use of the photoelectric element, and the durability and reliability of the photoelectric element are low.

  In addition, since no consideration has been given to the thickness of the ceramic substrate (submount material substrate) constituting the conventional submount material, even when an AlN substrate having high thermal conductivity is used, the thermal resistance is large. Therefore, there is also a problem that heat dissipation is insufficient.

  The present invention has been made in order to solve the above-mentioned problems. Even when a thermal shock is applied during an assembly process or use, the metal circuit layer is hardly peeled off, and is excellent in heat dissipation, durability and reliability. An object is to provide a substrate for a submount material.

  In order to achieve the above object, the present inventors prepared a submount material by forming a metal circuit layer by sputtering on an AlN substrate surface having various dimensions, thermal conductivity, and surface roughness. We compared the effects of specifications on thermal shock resistance and peel resistance. As a result, especially when the relationship between the thermal conductivity and the plate thickness of the ceramic substrate constituting the submount material is adjusted to a certain range, or the surface roughness of the ceramic substrate is regulated to a certain range, In addition to improving the heat dissipating property of the submount material, it was found that a submount material having excellent heat dissipating property and durability can be obtained for the first time, as it can effectively prevent peeling of the metal circuit layer. The present invention has been completed based on the above findings.

  That is, the submount material substrate according to the present invention is a submount material substrate using an aluminum nitride substrate having a thermal conductivity of 170 W / m · K or more, and the vertical and horizontal lengths of the aluminum nitride substrate are each 1 mm or less. The K / t ratio is 700 or more when the thermal conductivity of the aluminum nitride substrate is K (W / m · K) and the thickness is t (mm).

  Further, the submount material obtained by the present invention comprises a ceramic substrate made of a sintered body mainly composed of aluminum nitride, and a metal circuit layer formed on the ceramic substrate, for mounting a diode. In the submount material, the thermal conductivity of the ceramic substrate is K (W / m · K), and the K / t ratio is 700 or more when the thickness is t (mm). .

  Another submount material obtained by the present invention includes a ceramic substrate made of a sintered body mainly composed of aluminum nitride, and a metal circuit layer formed on the ceramic substrate, and is mounted with a diode. The surface roughness of the ceramic substrate is 0.1 to 0.5 μm on the basis of arithmetic average roughness (Ra).

  Furthermore, in the submount material, the width of the metal circuit layer formed on the surface of the ceramic substrate is preferably 100 μm or more. Moreover, it is preferable that the metal circuit layer formed on the ceramic substrate surface covers the entire ceramic substrate surface. Furthermore, it is desirable that the thermal conductivity of the ceramic substrate is 100 W / m · K or more. The thermal conductivity of the ceramic substrate is more preferably 170 W / m · K or more. Furthermore, it is more preferable that K / t ratio is 750-850.

  The ratio (K / t) of the thermal conductivity (W / m · K) to the thickness t (mm) of the ceramic substrate constituting the substrate for submount material of the present invention is good heat dissipation and resistance of the metal circuit layer. It is set to 700 or more to ensure both peelability. That is, the thermal conductivity K is high, and it is possible to improve the heat dissipating property of the submount material by reducing the thickness t, and at the time of mounting the diode chip by soldering to the submount material, 350 Even when a high temperature of ℃ or higher acts on the submount material, damage to the joint portion between the metal circuit layer and the ceramic substrate due to thermal shock is reduced, and peeling of the metal circuit layer can be effectively prevented.

  That is, the higher the thermal conductivity K of the ceramic substrate (submount material substrate) or the thinner the plate thickness t is, the more advantageous for improving the heat dissipation of the submount material. In order to prevent this, the ratio (K / t value) of the thermal conductivity K (W / m · K) of the substrate to the plate thickness t (mm) of the ceramic substrate is set to a range of 700 or more. A range of 850 is more preferred.

  The specific thickness t of the submount material substrate (ceramics substrate) of the present invention constituting the submount material varies depending on the thermal conductivity. That is, when an AlN substrate having a thermal conductivity of 200 W / m · K is used, the thickness t of the AlN substrate is set to 0.286 mm or less. When an AlN substrate having a thermal conductivity of 170 W / m · K is used, the thickness t of the AlN substrate is set to 0.243 mm or less.

  When the K / t ratio is in the range of 750 to 850, the thermal conductivity and the thickness of the AlN substrate are the most preferable ranges. Therefore, the vertical and horizontal lengths of the AlN substrate are 1 mm or less. Since the AlN substrate is less likely to be damaged when the submount material is produced, the yield can be improved.

  Further, the surface of the submount material substrate (ceramic substrate) of the present invention constituting the submount material is roughened, and the surface roughness is in the range of 0.1 to 0.5 μm on the basis of the arithmetic average roughness (Ra). By defining, the bonding strength of the metal circuit layer formed by the sputtering method can be improved by the anchor effect, and as a result, when excessive thermal shock acts when soldering the diode chip to the submount material In this case, peeling of the metal circuit layer from the ceramic substrate can be effectively prevented.

  In order to ensure the heat dissipation of the submount material, the thermal conductivity K of the ceramic substrate constituting the submount material is preferably 100 W / m · K or more, more preferably 170 W / m · K or more. Furthermore, when the surface of the ceramic substrate is actively roughened and the surface roughness is specified to be 0.1 to 0.5 μm on the basis of Ra, a metal circuit layer having a small circuit width is formed by sputtering. The circuit layer is affected by the irregularities on the surface of the ceramic substrate, and disconnection is likely to occur. Therefore, the width of the metal circuit layer is preferably set to 100 μm or more. In particular, the metal circuit layer is more preferably formed so as to cover the entire surface of the ceramic substrate.

  According to the substrate for a submount material according to the above configuration, the relationship between the thermal conductivity and the plate thickness of the ceramic substrate constituting the submount material or the surface roughness of the ceramic substrate is adjusted to a predetermined range. In addition to improving the heat dissipation of the mounting material, it is possible to effectively prevent the metal circuit layer from peeling off from the ceramic substrate even when a thermal shock is applied during assembly or use, and excellent heat dissipation and durability A submount material that combines with the above can be obtained. Therefore, by joining a diode to the submount material, it is possible to mass-produce photoelectric elements with excellent reliability with a high manufacturing yield.

  Next, embodiments of the present invention will be described more specifically based on the following examples and comparative examples.

[Examples 1 to 11 and Comparative Examples 1 to 5]
As shown in Table 1, aluminum nitride (AlN) sintered bodies having a thermal conductivity K of 160 to 202 W / m · K and a plate thickness t of 0.177 to 0.309 mm are prepared. By polishing the surface, AlN substrates having the surface roughness shown in Table 1 were prepared.

  Next, a Ti film having a thickness of 0.05 μm, a Pt film having a thickness of 0.2 μm, and an Au film having a thickness of 0.5 μm are sequentially formed on the surface of each AlN substrate by using a sputtering method. A metal circuit layer was formed. Next, each AlN substrate on which the metal circuit layer was formed was subjected to pattern etching treatment, and then cut into a 1 mm square shape using a dicing cutter, thereby preparing a large number of submount materials according to the respective examples and comparative examples.

  As shown in FIG. 1, the prepared submount material 4a has a Ti film 8 and a Pt film 9 having a predetermined thickness on the surface of an AlN substrate 2a having a predetermined surface roughness, thermal conductivity K, and plate thickness t. A metal circuit layer 3a having a three-layer structure with the Au film 10 is integrally formed.

  Next, in order to evaluate the thermal shock characteristics of each submount material prepared as described above, the following thermal shock test was performed. That is, each submount material was placed on a metal plate having a temperature of 400 ° C. for 1 minute in a nitrogen atmosphere and heated, and then immediately transferred to an aluminum plate having a temperature of 25 ° C., thereby quickly cooling. The thermal shock acting in this heating-cooling operation corresponds to the thermal history when the diode chip is solder-bonded to the submount material.

And after confirming the deterioration of the bonding strength of the metal circuit layer of each submount material after cooling, when the adhesive tape is peeled off at a constant speed after applying a commercially available adhesive tape to the surface of the metal circuit layer The ratio of the submount material with the metal circuit layer peeled to the total number of samples was measured, and the results shown in Table 1 below were obtained. In addition, about the peeling rate (%) of a metal circuit layer, 200 submount materials of each Example and a comparative example were each produced and measured.

  As is clear from the results shown in Table 1 above, in each example in which the relationship between the thermal conductivity K and the plate thickness t of the AlN substrate constituting the submount material or the surface roughness of the AlN substrate was adjusted to a predetermined range. In such a submount material, the peeling rate of the metal circuit layer is as small as 0 to 4%, and even when a thermal shock is applied, the metal circuit layer can be effectively prevented from peeling from the AlN substrate, and has excellent heat resistance. It was confirmed to have impact properties.

  In particular, in an example in which the K / t ratio is 700 or more and the surface roughness of the AlN substrate is 0.1 to 0.5 μm, the peeling rate of the metal circuit layer is 0%. It was found that a synergistic effect was obtained.

  In Example 7 where the K / t ratio is 960, the peeling rate of the metal circuit layer is as good as 0%, but since the plate thickness of the AlN substrate is thin, it has a 1 mm square shape as in the example. What was damaged when cutting was confirmed. Therefore, it can be said that the K / t ratio is the most effective range of 750 to 800. From this point of view, it can be said that the submount material of the present invention having a K / t ratio of 700 or more is particularly suitable as a small-sized submount material having a length and width of 1 mm square or less.

  On the other hand, in the submount material according to the comparative example in which the surface roughness of the AlN substrate is excessively low, it has been found that a high bonding strength of the metal circuit layer due to a sufficient anchor effect cannot be obtained and the occurrence rate of peeling increases. . Similarly, it was confirmed that the peeling rate of the metal circuit layer was high for the comparative example having a rough surface. This is considered to be because although the anchor effect is obtained by roughening the surface of the AlN substrate, it is difficult to form a sputtered film uniformly because the surface of the AlN substrate is too rough. In particular, a small submount material whose vertical and horizontal dimensions are 1 mm square or less is easily affected. Further, in the submount material according to the comparative example in which the pattern width of the metal circuit layer is set to be too small as 50 μm, the disconnection of the metal circuit layer occurs and the bonding strength of the entire circuit layer is reduced, so the occurrence rate of peeling is also Rose.

Sectional drawing which shows one Example of the submount material which concerns on this invention. Sectional drawing which shows the structural example of the photoelectric element which mounted the diode in the submount material.

Explanation of symbols

1 Laser diode light emitting element 2, 2a Ceramic substrate (AlN substrate, submount substrate)
3, 3a Metal circuit layers 4, 4a Submount material 5 Solder layer 6 Laser diode 7 Heat sink 8 Ti film 9 Pt film 10 Au film

Claims (4)

In the substrate for a submount using an aluminum nitride substrate having a thermal conductivity of 170 W / m · K or more, the vertical and horizontal lengths of the aluminum nitride substrate are each 1 mm or less, and the thermal conductivity of the aluminum nitride substrate is K ( A substrate for a submount material, wherein the K / t ratio is 700 or more when W / m · K) and the thickness is t (mm). 2. The substrate for a submount according to claim 1, wherein the surface roughness of the aluminum nitride substrate is 0.1 to 0.5 [mu] m on the basis of arithmetic average roughness (Ra). The submount material substrate according to claim 1, wherein the K / t ratio is 750 or more and 850 or less. The submount material substrate according to any one of claims 1 to 3, wherein the aluminum nitride substrate is for mounting a diode.

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