JPH0129067B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a heat sink used for increasing heat dissipation in semiconductor light emitting devices, etc.
In particular, the present invention relates to a heat sink structure that allows electrical connections to be made freely and reliably.

(b) Prior art and problems Semiconductor light-emitting devices such as semiconductor lasers generate a large amount of heat during operation and are sensitive to temperature, and the thermal energy generated within the semiconductor element is released to the outside of the device. Generally, a semiconductor chip is fixed onto a stem via a heat sink, as shown in FIG. In FIG. 1, 1 is a semiconductor chip, 2 is a heat sink, and 3 is a semiconductor chip.
4 is a stud, 4 is a stem, 5 is a lead terminal, and 6 is a bonding wire.

Conventionally, a heat sink is made of a cubic or rectangular parallelepiped diamond or silicon whose surface is coated with a metallic flux such as gold or tin (Au Sn) alloy. A semiconductor chip is placed on top of this and heated to melt it. The chips are bonded by melting the material. In many lasers, p-side and n-side electrodes are respectively provided on two opposing main surfaces of a semiconductor chip, and the electrodes on the main surface side that are in contact with the heat sink 2 are made of metal fused metal coated on the surface of the heat sink 2. It is connected to the stem 4 by the material and the stud 3, and the electrode opposite thereto is connected to the lead terminal 5 by the bonding wire 6.

However, in such an unbalanced structure, in order to improve the characteristics and reliability of the laser etc., it is necessary to select the conductivity type of the semiconductor substrate and semiconductor layer, and to make the adhesive surface to the heat sink the substrate side or the active layer side. This selection may conflict with the requirements for the potentials of both electrodes from the standpoint of using this, and it may be necessary to reverse the terminal connections.

In this case, for example, as illustrated in FIG. 2, instead of the heat sink 2 in which the entire surface of the conventional heat sink 2 is coated with a metallic flux, a heat sink having a metal film coated only on the semiconductor chip bonding surface and the stud bonding surface. 12 is bonded with a metallic flux in the same manner as in the previous example, and the metal film on the semiconductor chip adhesion surface of the heat sink 12 and the lead terminal 5 are connected by a bonding wire 16, and the upper side of the semiconductor chip 1 is bonded. By connecting the electrodes of the studs 3 to, for example, the bonding surface of the heat sink 12 using bonding wires 17, it is possible to reverse the terminal connection.

However, if the metal film is coated on the entire surface of the heat sink 12 to which the semiconductor chip is attached, when the metal flux is applied by heating and melting on this surface, the metal flux spreads over the entire surface of the metal film. There is a problem that the bonding area necessary for connecting the bonding wire 16 cannot be secured.

(c) Purpose of the Invention The present invention provides a structure for a heat sink used in, for example, a semiconductor laser, which allows electrical connections to be made freely and reliably, independent of mechanical adhesion and thermal conduction. The purpose is to

(d) Structure of the Invention The object of the present invention is to form isolated groove-like recesses of the same shape in the vicinity of the four corners of the metal film adhered to the main surface of the square flat plate substrate excluding the side surfaces. This can be achieved by a heat sink carved on one surface in a 4-fold symmetrical manner and leaving a bonding area.

In particular, the groove-like recesses are provided on the first surface and the second surface, and the groove-like recesses are arranged symmetrically within each surface and between the two surfaces, so that the assembly can be improved. There is a large degree of freedom in the direction of the heat sink during work, and work efficiency is not impaired.

(e) Embodiments of the Invention The present invention will be specifically explained below using embodiments with reference to the drawings.

FIG. 3a is a perspective view showing an embodiment of the heat sink of the present invention. In the figure, 21 is a base made of silicon (Si) single crystal, and 22 is titanium (Ti).
The film 23 is a platinum (Pt) film, and 24 is a gold (Au) film. In this example, an L-shaped groove-shaped recess 25 is formed by selectively removing the Au film 24. , are provided in the vicinity of the four corners of both the upper and lower surfaces in a four-fold symmetrical manner in the same isolated shape, leaving bonding regions 27.

This heat sink is manufactured, for example, as follows. That is, a Ti film 22 with a thickness of, for example, about 70 [nm] and a Pt film 23 with a thickness of, for example, about 50 [nm] are formed on both sides of a Si substrate having a resistivity of about 1 [KΩcm] and cleaned with trichlorethylene and acetone. It is formed by a method such as sputtering or electron beam evaporation. Next, a resist mask is formed on the pattern 25 and the scribe lines on one surface by lithography, and Au is plated to a thickness of about 5 μm, for example, by electroplating to form the Au film 24. selectively formed. After the resist mask is peeled off and removed, an Au film 24 is similarly formed on one surface remaining by aligning both masks. A heat sink is completed by cutting this Si substrate at the scribe line. The dimensions of the heat sink in this example are approximately 0.7 x 0.7 x 0.3 [mm ³ ], and the pattern of the L-shaped groove-shaped recesses 25 has a side length of approximately
100 [μm], width approximately 25 [μm], distance between each other approximately 350
[μm].

FIG. 3b is a schematic diagram showing the assembled state, in which the laser chip 1 is adhered to the heat sink of this embodiment with a metal fusion material 26. The metallic fusion material 26 spreads on the surface of the Au film 24, but the spread is prevented by the groove-shaped recess 25, and a bonding region 27 for the wire 16 is secured.

Furthermore, as in this embodiment, by symmetrically arranging the putters of the groove-shaped recesses 25 on both the upper and lower surfaces, there is no means for preventing the spread of the metallic material, and the metal is uniformly distributed over the entire surface of the upper and lower surfaces. It can be assembled without any directional constraints, just like a heat sink provided with a membrane or a heat sink coated on all surfaces.

In the above embodiment, Si is used for convenience of pattern formation.
Although a substrate is used, the invention can also be practiced with substrates such as diamond, sapphire, or beryllia porcelain. Further, in this embodiment, the area of the recess 25 is formed by chipping the Au film 24, but the formation of this recess may be caused by, for example, removing the metal film altogether, or by providing a recess in the base and removing the metal. Other methods such as creating a step on the surface of the film may also be used.

(f) Effects of the Invention As explained above, according to the present invention, a wiring connection area is secured on the heat sink surface, and electrical connection can be freely and reliably performed independent of mechanical connection and thermal conduction. It is also possible to create a structure that does not reduce workability, and is highly effective in the construction of semiconductor lasers and the like.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing an example of an assembled structure of a semiconductor laser, and FIGS. 3 a and 3 b are perspective views showing an embodiment of the present invention. In the figure, 1 is a semiconductor chip, 2 and 12 are heat sinks, 3 is a stud, 4 is a stem, 5 is a lead terminal, 6, 16 and 17 are bonding wires, 21 is a Si substrate, 22 is a Ti film, and 23 is a PT film. ,
24 is an Au film, 25 is a groove-shaped recess, 26 is a metal flux, and 27 is a bonding region.

Claims (1)

[Scope of Claims] 1 Isolated groove-like depressions 25 of the same shape are formed in a four-fold symmetrical manner near the four corners of the metal film adhered to the main surface of the square flat substrate 21 excluding the side surfaces. In addition, the heat sink is carved so as to leave a bonding area 27. 2 Groove-shaped recess 25 carved in the 4-fold symmetrical pattern
However, on both the upper and lower main surfaces,
The heat sink according to claim 1, characterized in that the heat sink is symmetrically provided.