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Heat sink and laser diode

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Heat sink and laser diode


The present invention is directed to improve reliability by preventing deterioration in the structure of an inner wall of a water channel caused by galvanic corrosion. A heat sink in which a water channel of a cooling fluid is formed by stacking and bonding a plurality of thin plates, in which a surface in the water channel is made of the same metal material except for at least an end of a bonded part of the thin plates.
Related Terms: Water Channel

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Inventors: Kenji Sasaki, Hidekazu Kawanishi, Yuichi Hamaguchi
USPTO Applicaton #: #20120291995 - Class: 16510411 (USPTO) - 11/22/12 - Class 165 
Heat Exchange > Intermediate Fluent Heat Exchange Material Receiving And Discharging Heat

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The Patent Description & Claims data below is from USPTO Patent Application 20120291995, Heat sink and laser diode.

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RELATED APPLICATION DATA

This application is a division of U.S. patent application Ser. No. 12/128,142, filed on May 28, 2008, the entirety of which is incorporated herein by reference to the extent permitted by law. The present invention claims priority to and contains subject matter related to Japanese Patent Application No. JP 2007-144640 filed in the Japanese Patent Office on May 31, 2007, the entire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat sink in which a channel (water channel) of a cooling fluid is formed by stacking and bonding a plurality of thin plates and to a laser diode obtained by mounting a semiconductor laser device in such a heat sink.

2. Description of the Related Art

In a laser diode of a few W to tens W class, a water cooling system is often employed to realize a higher output and higher reliability. As a heat sink structure for realizing high heat exhaust efficiency, a heat sink of a micro-channel type is well known (refer to, for example, Japanese Unexamined Patent Application Publication No. 2006-294943).

FIG. 8 shows an example of a sectional structure of a laser diode of the related art.

The laser diode is constructed by mounting a semiconductor laser chip 102 on a heat sink 101 having a fine channel structure of a micro-channel type. The heat sink 101 has a structure obtained by stacking and bonding a plurality of thin plates. In the heat sink 101, a water channel 103 (a supply water channel 103A, an intermediate water channel 103B, and an exhaust water channel 103C) through which a cooling fluid passes is formed. In the example of FIG. 8, five thin plates of a first layer 121 as a top layer to a fifth layer 125 are stacked. The first layer 121 is a laser chip mounting plate on which the semiconductor laser chip 102 is mounted. In the second and fourth layers 122 and 124, a radiator fin is formed. In the second to fifth layers 122 to 125, a hole for forming the water channel 103 is formed. The layers are bonded with an insert metal (bonding metal) 105.

A concrete manufacturing procedure of the heat sink 101 having such a structure includes the following steps. (1) manufacture of base sheets of the layers (2) etching of sheet materials (formation of a water channel structure) (3) plating of the sheet materials with an inert metal (bonding metal) (4) bonding of the sheet materials (5) heating and pressure-bonding of the sheet materials

As the material of the base sheet, generally, copper (Cu) having high heat conductivity and which is processed easily is used. As the insert metal 105, for example, gold (Au) or silver (Ag) is used. As a bonding method, liquid-phase diffusion bonding, soldering, or the like is used.

SUMMARY

OF THE INVENTION

In the above-described manufacture procedure, to prevent a fine structure part from being buried by the insert metal 105 which is melt at the time of performing liquid-phase diffusion bonding or the like, the second and fourth layers 122 and 124 in which the pattern of the radiator fin is formed are not plated with the insert metal 105 but the first, third, and fifth layers 121, 123, and 125 are plated with the insert metal 105 as shown in FIG. 9. When bonding is performed after alternately plating the layers, as shown in FIG. 8, different metals appear in the inner wall of the water channel 103. Specifically, a part 201 in which the metal (copper or the like) of the base material and a part 202 in which the insert metal 105 (gold, silver, or the like) is exposed mixedly exist in the water channel 103. Due to such a structure, in the past, there is an issue such that galvanic corrosion occurs with use time. The galvanic corrosion denotes a phenomenon such that when dissimilar metals come into contact in the cooling fluid, ions move, and the metal having a lower ionization tendency is thinned (etched). When a potential difference occurs between dissimilar metals in the heat sink via the cooling fluid and water is passed for a long period of about thousands of hours, a noble metal side (for example, gold or silver) in the heat sink is thinned and a corrosion product is deposited and adhered onto a base metal side (for example, copper). Due to the phenomenon, destruction of the structure in the water channel (decrease in the cooling capability in a few thousands of hours of passing of water) and continuity with the heat sink outer wall (water leakage in a few thousands of hours of passing of water) occurs. It largely deteriorates the reliability of the heat sink.

It is desirable to provide a heat sink and a laser diode realizing improved reliability by preventing deterioration in the structure of an inner wall of a water channel due to galvanic corrosion.

According to an embodiment of the present invention, there is provided a heat sink in which a water channel of a cooling fluid is formed by stacking and bonding a plurality of thin plates. A surface in the water channel is made of the same metal material except for at least an end of a bonded part of the thin plates.

According to an embodiment of the invention, there is provided a laser diode including a heat sink in which a water channel of a cooling fluid is formed by stacking and bonding a plurality of thin plates, and a semiconductor laser device mounted on the heat sink. The surface in the water channel in the heat sink is made of the same metal except for at least an end of a bonded part of the thin plates.

In the heat sink or the laser diode of the embodiment of the present invention, in the water channel, the surfaces made of the same metal material including the end of the bonded part are exposed, or the surfaces made of the same metal material excluding an end of the bonded part are exposed. With the configuration, the surfaces in the water channel are made of substantially the same metal material, and no dissimilar metals exist in the water channel. Consequently, even when dissimilar metals exist, the amount of the dissimilar metals is very small in the surface area of in the water channel. Thus, galvanic corrosion is minimized, and reliability improves.

In the heat sink and the laser diode of the embodiment of the present invention, the surfaces in the water channel are made of the same metal material except for at least an end of a bonded part of the thin plates. Consequently, dissimilar metals do not exist or hardly exist in the surface area in the water channel. As a result, deterioration in the structure of the inner wall of the water channel caused by galvanic corrosion is prevented, and reliability may be improved.



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stats Patent Info
Application #
US 20120291995 A1
Publish Date
11/22/2012
Document #
13564250
File Date
08/01/2012
USPTO Class
16510411
Other USPTO Classes
International Class
28D15/00
Drawings
10


Water Channel


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