JPH11251688A - Cap for electronic part and semiconductor laser using the cap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cap for electronic parts which has a window section having window glass, etc., in its top section and is constituted in such a struc ture that the glass, adhesive, etc., of the window section is not cracked nor broken, even when the fitting size of the cap is not severe at the time of hermeti cally sealing the cap on a stem by press fitting and a semiconductor laser using the cap. SOLUTION: A light transmitting member 15 is stuck to the window section 13 of a cylindrical metallic shell having the window section 13 in its top section and an opening 14 which can be joined with a stem in its bottom section, and a step section 11a is formed on the internal surface of the cylindrical section 11 of the shell so that the wall thickness of the section 11 on the opening section 14 side may become larger than that on the top section side. A semiconductor laser is formed by mounting a laser chip on a heat sink fixed to the stem and press fitting the cap in the periphery of the laser chip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cap for electronic parts, such as a can-seal type semiconductor laser, comprising a metal shell having a window at the top and an opening at the bottom to be joined to the stem. More specifically, by performing a hermetic seal by pressing the cap into the stem,
The present invention relates to a cap for an electronic component such that glass of a window portion of the cap is not damaged even when a strong external pressure is applied from an upper surface of the cap of the electronic component in which the cap is assembled, and a semiconductor laser using the same.

[0002]

2. Description of the Related Art A can-seal type semiconductor laser has a structure as shown, for example, in FIG. In FIG. 7A, a laser chip 23 is mounted on a heat sink 21a integrated with a stem 21 via a silicon submount 22.
In this stem 21, a lead 26 is insulated from the stem 21 and hermetically sealed (hermetically sealed), and a lead 28 is connected to the stem 21 by welding or the like.
One electrode terminal of the laser chip 23 is wire-bonded to the lead 26 via the silicon submount 22. The other electrode of the laser chip 23 is connected to the lead 28 via the heat sink 21a. A cap 24 is hermetically sealed around the periphery of the stem 21 by welding or the like.

A laser chip 23 is provided on the top of the cap 24.
A window with a through hole is provided to extract light from
In order to make the inside airtight, a window glass 25 is bonded with a low melting point glass (not shown) or the like. The cap 24 is welded to the stem 21 in a state where the window glass 25 is bonded to the cap 24 in advance. This welding is often performed by electric resistance welding. In this case, as shown in FIG.
A projection 24a on the bottom of the cap 24
Are formed. Not only semiconductor lasers but also caps that have windows and are used for hermetic sealing include those used for phototransistors, photodiodes, and light emitting diodes (LEDs) with metal caps.
The structure is as shown in FIG.

On the other hand, in the above-described structure, a hermetic seal must be obtained by welding with a stem when a cap is attached. However, welding conditions vary widely and a stable hermetic seal cannot be obtained. Since there is a problem that the capping is difficult, as disclosed in Japanese Patent Application Laid-Open No. 9-283852, a structure in which a cap is pressed into a stem to obtain a hermetic seal has been attempted.

[0005]

As described above, when the cap to which the window glass is sealed is press-fitted, cracks or cracks easily occur in the window glass or the low melting point glass of the adhesive. . Therefore, Japanese Patent Application Laid-Open No. 9-28385
In Japanese Patent Application Publication No. 2 (1993) -1995, in order to solve the problem, a projection is formed in a ring shape on the outer peripheral surface of the top, but when mass production is performed by an automatic machine, it is shown in FIGS. As described above, the dimensional difference between the inner diameter A of the cap 24 and the outer diameter B of the fitting portion of the stem 21 (B is larger than A) is 10 to 20 μm.
If it is not controlled to an appropriate degree, an external force is applied to the bonding portion at the time of press-fitting, and the window glass 25 may be peeled off. There's a problem. In FIG. 6, 2
9 is an adhesive such as a low melting point glass.

The present invention has been made in order to solve such a problem, and when a cap having a light transmitting member such as a window glass at a top window portion is hermetically sealed to a stem by press-fitting, the dimensional relationship is reduced. It is an object of the present invention to provide an electronic component cap having a structure in which a glass or an adhesive of a window does not crack or break even if it is not severe.

Another object of the present invention is to facilitate parts management,
In addition, it is an object of the present invention to provide a semiconductor laser having a structure in which a window is not damaged while employing a simple assembling method of press-fitting a cap into a stem.

[0008]

According to the present invention, there is provided a cap for electronic parts according to the present invention, wherein a window is formed at the top and an opening is formed at the bottom of the cylindrical metal shell. An electronic component cap to which a transparent member is adhered, wherein a step portion is formed in the cylindrical portion of the metal shell such that a thickness of the opening side is smaller than a thickness of the top side.

With this structure, when the cap is pressed into the stem, the pushing force applied to the opening at the bottom of the cap is absorbed by the thin portion of the cylindrical portion, and the thick portion of the upper portion is thick. The part is hard to apply force. Therefore, the force applied to the window glass or the low-melting glass of the adhesive, which is bonded to the window, is very weak, and cracks and cracks are hardly generated.

[0010] By forming the projection in a ring shape on the outer peripheral surface of the top of the metal shell, the light transmitting member such as a window glass and the bonding portion thereof become strong even against the pressing force from above, and The peeling of the window is reduced, and the reliability is improved.

The semiconductor laser of the present invention has a stem, a laser chip mounted on a heat sink provided on the stem, and a cylindrical portion having a window at the top and fitting the stem at the bottom. A light-transmitting member is fixed to the window portion, and the cylindrical portion is formed such that the thickness of the cylindrical portion is small on the stem side, and the cap portion is formed thick on the top side. And is fitted to the stem by press fitting.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an electronic component cap according to the present invention will be described with reference to the drawings.

The electronic component cap 10 of the present invention is shown in FIG.
As shown in the cross-sectional explanatory view of one embodiment, a window 13 is formed at the top of a cylindrical portion 11 of a metal shell, and an opening 14 that can be joined to a stem is formed at the bottom.
Then, a light transmitting member 15 such as glass or plastic is adhered to the window 13 by an adhesive 16 such as low-melting glass so that airtightness can be maintained. The cylindrical portion 11 of the metal shell has a thickness t on the opening 14 side.
Is characterized in that the step portion 11a is formed so as to be thinner than the thickness T on the top side.

The metal shell having the window 13 at the top of the cylindrical portion 11 is formed by drawing a Kovar plate or the like, for example. At the time of drawing, a through-hole serving as a window 13 is provided at the top, and an opening 14 for joining to the stem is provided at the bottom. The aforementioned step 11
“a” is formed by providing a step in the convex mold at the time of drawing, and can be thinner on the opening 13 side and thicker on the top side. The difference between the thinner part and the thicker part may be such that the force at the time of press-fitting can be absorbed by the thinner part and is not transmitted to the thicker top part as much as possible. If the material is formed as thin as possible using a Kovar plate, the thinner part is about 0.13 to 0.17 mm, and the thicker part is about 0.05 mm thicker. The window portion 13 is for letting a laser beam or the like of a laser chip enclosed therein pass therethrough, or for passing a light to be received.
It is necessary to transmit light, but on the other hand, to hermetically seal the inside and protect elements such as laser chips,
A light transmitting member 15 such as a window glass is adhered by an adhesive 16 such as a low melting point glass.

As a specific example of the cap used in the semiconductor laser, for example, in the structure shown in FIG. 1, the height L of the cap 10 is about 3 mm, the outer diameter D is about 2.5 mm, and the thickness t of the thin portion is small. It is formed so as to have a thickness of about 0.15 mm (inner diameter A is about 2.2 mm) and a thick portion T having a thickness of about 0.2 mm.
The position M from the lower end where the step 11a is provided
Is provided in a range of about 1.4 to 2.2 mm. That is, the height of the fitting portion with the stem is 1.4 mm from the lower end.
The lower surface of the window glass is located at a position of about 2.15 mm from the lower end (the thickness of the window glass is about 0.2 mm), which is within the range.

In the example shown in FIG.
A ring-shaped projection 12 is formed on the outer peripheral end of the upper surface of the top portion of the top. The projections 12 are also provided to prevent cracks in the window glass. In other words, when pressure is applied to the entire surface of the top of the cap to press it into the stem, a tensile force is applied to the window glass and the low melting point glass portion used as an adhesive, and cracks and cracks are likely to occur. This is because, by being provided, a pulling force does not act on the window glass 15 portion, and the force is easily transmitted to the lower end portion side via the cylindrical portion 11. This projection 12 has a height H
Are formed to have a width of about 0.03 mm and a width W of about 0.25 mm.

Next, using a window glass as the light transmitting member 15 and a cap 10 bonded with a low-melting glass as the adhesive 16, the position from the lower end of the step portion 11a is fixed at 1.4 mm, and After changing the difference (BA) between the inner diameter A of 10 and the outer diameter B of the stem in various ways, press-fitting the cap to the stem at about 15 to 20 kg, the load when the window glass falls off by 20 samples at a time. Was examined. FIG. 2 shows the results of comparison between the cap S of the present invention and the conventional cap R having no step. The conditions for press-fitting the cap 10 are as shown in FIG.
The plate-shaped pressurizer 1 is placed on the stem 5, and the entire surface of the upper surface of the cap 10 is hit while the center of the cap 10 and the stem 5 is held by the cap guide 18.
9, a load was applied in the direction of arrow P and press-fitted. And it measured by measuring the load at the time of window glass falling off with a tension gauge after thickening. Note that FIG. 2 also shows a case where a load is applied to the cap alone without press-fitting the stem, in order to clarify the distinction from a load that causes the window glass to fall off based on the cap alone not due to fitting.

Further, assuming that BA is constant at 20 μm,
When the position M of the stepped portion is variously changed in the range of 1.4 to 2.2 mm and the lower end of the cap is fitted to the outer periphery of the stem to a depth of 1.2 mm with a setting of a constant load of 17 kgf, the adhesive Maximum principal stress (k
gf / mm ² ) was determined by simulation. The result is shown in FIG.

As is apparent from FIG. 2, according to the conventional cap R having no step, BA, that is, the overlapping dimension between the inner diameter of the cap and the outer diameter of the stem is 20 mm.
When the thickness exceeds μm, the load at which the window glass falls off (does not break) sharply decreases, but according to the cap S of the present invention, the load at which the window glass falls off hardly changes even at about 40 μm. That is, even if there is a variation in fitting between the cap 10 and the stem, the window glass does not break and fall off. In the manufacturing process of the cap or the stem described above, there is almost no variation in the fitting dimension exceeding 40 μm. There is no. Further, as is apparent from FIG. 3, the maximum principal stress of the stepped portion of 1.4 mm or more is half that of the conventional one in which the stepped portion is not provided (the position M of the stepped portion is 0). From this result, it can also be seen that the formation of the step portion reduces the stress on the low-melting glass. As for the position M of the stepped portion, the smaller the value is, the larger the load at the time of press-fitting needs to be increased even if the fitting is the same, and it cannot be generally said that the smaller the position M of the stepped portion is, the better.

Next, a semiconductor laser of the present invention using the cap will be described with reference to FIG. FIGS. 5A and 5B are cross-sectional views taken along planes that are shifted by 90 °.

5 (a) and 5 (b), reference numeral 1 denotes a cylindrical shape formed by drawing and punching from a sheet of iron or copper metal material having a thickness of about 0.2 to 0.4 mm. The ring has a heat sink 1a which is bent so as to extend upward, and a submount 6 on which a laser chip 7 is mounted is bonded. A flange 1b is provided at the bottom of the cylindrical ring 1 with a width of about 0.3 mm, and a common lead 1c extends downward from a part of the flange 1b. This heat sink 1a
The common lead 1c can be easily formed by simply punching and bending the lead frame. In addition, in the collar portion 1b,
A notch for positioning in the rotational direction is provided, but is not shown. Leads 3 and 4 insulated and held by an insulator 2 such as glass are hermetically sealed in the ring 1, and a stem 5 is formed by the cylindrical ring 1, the insulator 2 and the leads 3 and 4. .

A submount 6 to which a laser chip 7 is bonded is conveyed to the heat sink 1a by a suction collet, aligned and mounted. The alignment of the submount 6 is performed using the surface F of the flange 1b of the ring 1 as a reference plane. By doing so, when the semiconductor laser is mounted on a set such as a CD player or the like, since the surface F of the flange portion 1b is used as a reference, accurate positioning can be performed.

The submount 6 is formed of a silicon substrate, for example, and is provided to facilitate assembling a small laser chip 7 of about 200 μm × 150 μm. In this example, a light receiving photodiode (not shown) for monitoring the light emission amount of the laser chip 7 is formed on the submount 6 made of a silicon substrate. The laser chip 7 and each electrode of a photodiode (not shown) are connected to the leads 3 and 4 by wire bonding with gold wires 8 respectively. The other electrode of each of the laser chip 7 and the photodiode is a submount 6
Are connected to the common lead 1c via the back surface of the stem 5 and three leads 1c, 3, 4 extend to the back surface side of the stem 5.

A semiconductor laser is manufactured by press-fitting the cap 10 shown in FIG. 1 to the outer peripheral wall of the cylindrical ring 1 of the stem 5 on which the laser chip 7 is mounted. That is, for example, the outer diameter of the cylindrical ring 1 is about 2.23 mm, and the inner diameter of the lower end of the cap 10 is 2.2.
It is formed to a thickness of about 0 mm, and is manufactured by press-fitting under the same method and conditions as shown in FIG.

In the above-described example, the projection is provided on the outer periphery of the top of the cap. However, by providing the projection, the concentration of the load on the window with respect to the load from the upper surface of the cap is avoided. However, the provision of the stepped portion without the protruding portion makes it possible to suppress the influence of variation in the fitting of the fitting portion between the cap and the stem.

[0026]

According to the present invention, although the difference between the outer diameter of the stem and the inner diameter of the cap had to be suppressed to about 10 to 20 μm in the past, according to the present invention, it is doubled (40 μm).
Even in the case of m), there is no influence of the stress on the window, and the variation in fitting between the cap and the stem can be largely tolerated. Therefore, it is not necessary to strictly control the dimensions of the stem and the cap, and the manufacturing control is facilitated, and the productivity is improved and the system can be adapted to mass production. As a result, an inexpensive and highly reliable electronic component such as a semiconductor laser can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of one embodiment of an electronic component cap of the present invention.

FIG. 2 is a diagram showing a relationship between a degree of fitting with a stem and a load at which a window glass falls when the cap of FIG. 1 is used.

FIG. 3 is a diagram illustrating a relationship between a position of a step portion of a cap and a maximum principal stress applied to the low-melting glass.

FIG. 4 is an explanatory view of a state where a cap is pressed into a stem.

FIG. 5 is an explanatory sectional view of a semiconductor laser using the cap of FIG. 1;

FIG. 6 is an explanatory diagram of a relationship between an inner diameter of a cap having a structure in which the cap is pressed into the stem and an outer diameter of the stem.

FIG. 7 is an explanatory diagram of a conventional semiconductor laser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cap 11 Cylindrical part 11a Step part 13 Window 14 Opening 15 Light transmission member

Claims (3)

[Claims] 1. A cap for an electronic component, wherein a light transmitting member is adhered to said window of a cylindrical metal shell having a window formed at a top and an opening formed at a bottom capable of being joined to a stem. An electronic component cap in which a step portion is formed such that a thickness of the cylindrical portion of the metal shell on the opening side is smaller than a thickness on the top side. 2. The electronic component cap according to claim 1, wherein a projection is formed in a ring shape on an outer peripheral surface of a top portion of the metal shell. 3. A stem, a laser chip mounted on a heat sink provided on the stem, and a cylindrical portion having a window at a top and a fitting portion with the stem at a bottom. A light-transmitting member is fixed to the window portion, and the cylindrical portion has a small thickness on the stem side, and the top portion is formed thick on the stem. A semiconductor laser fitted by press fitting.