JPH0119269B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for manufacturing a semiconductor device having at least one semiconductor circuit element and a protective envelope, comprising: providing a plate with electrically insulating and heat conducting properties with a metallized surface; a semiconductor circuit element is mounted on one side thereof, the board itself is placed on an electrically and thermally conductive support, and the board is surrounded by a frame of electrically insulating material; A semiconductor device comprising a connecting conductor on this frame, placed on a support, a cover on top of it, and the entire assembly consisting of this plate, the support, and the frame and cover that constitute a protective envelope. This relates to an assembly method.

The method according to the invention is particularly suitable for semiconductor devices which are to be operated in a very high frequency range, for example in the GHz range. However, the object of the present invention is not limited to this.

In the field of semiconductor devices that operate in high frequency ranges, special attention should be paid to the length of the connection wires that connect the semiconductor circuit elements to the metallized surface of the various elements, and the connection wires provided in the envelope or the connection wires that connect to the conductors. It is known that it costs money. As is known, the length of these connecting lines determines the inductance value of that line. Generally speaking, transistors and MOS (metal oxide semiconductors)
There are many connection points in a high frequency semiconductor device including a capacitor. Connection lines terminate at these connection points, and connection lines emanate from these connection points.

In the manufacturing method which is the object of the present invention, a subassembly, conventionally consisting of a plate generally made of beryllium oxide, a frame generally made of alumina, and a support generally made of copper, is produced in one first step. Was. In this case a plate of relatively small dimensions compared to the surrounding frame was soldered directly onto the support. This frame was fixed to the support using metal rings. This metal ring was located between the frame and the support and was fixed to the two parts by soldering. The use of this ring reduces the contact surface between the frame and the support, thereby reducing mechanical stress. In some cases, this method increases the dimensions of the frame so much that the frame breaks at the moment of soldering. 1
The one or more semiconductor devices are mounted on the plate of the thus formed subassembly by disposing soldering material and securing the required connection lines. Finally, place the cover and secure it by soldering.

These conventional assembly methods had several drawbacks.

First, experience has shown that it has been impossible to center the board correctly with respect to the surrounding frame. During the assembly of the subassemblies consisting of plates, frames, and supports, the plates and frames shift relative to each other and end up occupying considerably different positions in each completed subassembly. . However, the regularity of the connecting lines to be formed is determined by the relative position of this plate and frame.

Second, it will be appreciated that the connections of the plate and frame to the support must be able to withstand the temperatures reached in the subsequent soldering process of one or more semiconductor components.

This temperature is approximately 380° C. (this is the case when a plate coated with a gold layer is soldered to a crystal, and a gold-silicon eutectic layer is formed on the surface of the crystal). In this case, the plate and frame are therefore fixed by means of soldered inserts. Its melting temperature is significantly higher than 380℃ (generally 790
made of a copper-silver alloy that melts at ℃). As can be easily seen, at such temperatures it is difficult to avoid rejects, both due to breakage and splitting of the frame and plate and due to incorrect positioning of these two parts relative to each other. It was.

Finally, difficulties were encountered in securing the circuit elements in the correct location on the surface of the board. This is particularly the case when it is necessary to locate the circuit elements close to the frame wall, since this wall protrudes higher than the board.

The method according to the invention aims to overcome each of the drawbacks of the conventional methods mentioned above.

The method includes, as a first step, forming a subassembly comprising a circuit element, a plate, and a frame, securing a semiconductor circuit element on one of the metallized surfaces of the plate, and connecting the subassembly. by a wire to at least said connecting conductor, and then a second
The process is characterized in that this subassembly is connected on the one hand to the support 4 and on the other hand to the cover.

By using the method of the invention, a first advantage is that it is possible to reduce the temperature during the assembly of the plate and the frame to the support. This is because one or more circuit elements are prefixed to the plate during the assembly process. When using the method of the present invention, unlike conventionally known methods, the melting temperature is
Soldering materials lower than 380℃ can be used. In particular, gold (80%) and tin (20%)
It is advantageous to use a material with a melting point of 280° C. made from a eutectic of In this case, the assembly temperature is considerably lower than the 790 DEG C. in the previously known process, so that the risk of defective products due to damage to the ceramic elements, the formation of splits or the formation of cracks is much smaller. This method of assembly is also much easier and much faster due to the lower temperatures. Furthermore, since the frame is directly supported on the support, there is no need to interpose a metal ring between these elements to cancel out differences in thermal expansion coefficients.

A second important advantage of the method according to the invention is that the plate is positioned very precisely relative to the frame;
And it will be possible to maintain this.

Such precise positioning is obtained during the connecting line installation process. The connecting wires extending from the plate to the frame constitute a very tight wiring support network that stably positions the plate relative to the frame. This allows the lengths of the connecting lines between the several subassemblies to be very regular, which improves the reproducibility of the electrical properties.

Another advantage of the method of the invention is that it simplifies the process of soldering semiconductor circuit elements onto a board. The same is true if these circuit elements are located near the edges of the plates. This soldering process is actually performed prior to making the connection between the board and the frame, and during this soldering process, the frame that has not yet been placed does not interfere with the movement of the tool. do not have. Furthermore, even if defective products are produced, they are generated during the process of soldering the circuit elements to the board, and as in the assembly method using conventionally known technology, the three parts of the board - frame - support body are soldered.
It is not something that comes out during the assembly process.

In the method of the invention, only the connecting wires required for the electrical operation of the semiconductor device are sufficient to maintain the mechanical position between the plate and the frame. In conventional high-frequency devices, the weight of the plate is approximately 0.1 g, whereas the number of connection wires is often extremely large. These connecting lines have a diameter of 25 to 50 μm, which is sufficient to hold the subassembly parts in the correct position.

In the application of the method of the invention, the mechanical strength between the metallized surface of the plate and the frame can be maintained partly by the connecting wires and partly by the reinforcing wires connecting them. can. These reinforcing wires have a purely mechanical function.

The present invention will be explained below with reference to the drawings.

In the accompanying drawings, details of elements whose construction is well known have been omitted for clarity. Semiconductor elements in the form of semiconductor circuit elements, such as transistors or MOS capacitors, are shown only schematically.
Further, each component whose size is extremely small is shown enlarged to facilitate understanding.

In the assembly method shown in the drawings, the assembly is shown using semiconductor circuit elements such as a transistor 1 and a MOS type capacitor 2 as an example. These circuit elements are arranged on the metallized or upper surface 3A of the beryllium oxide plate 3. Transistor 1 is soldered on the back side of its crystal to surface 30. Capacitor 2 is soldered onto the other surface 31. This surface 31 and another surface 32 extend on the side of the plate 3 and are connected to the bottom surface 3B of the plate 3, which is also metallized. This plate 3 is fixed to a copper support 4 by its bottom surface 3B.

This plate 3 is covered with an alumina frame 5, and the gap (clearance) between these two elements is approximately
It is about 0.5mm. The frame 5 has a narrow upper ring 5B and a lower ring 5A with a metallized section between them. Both rings are connected to each other during manufacture of the frame so that they form an integral part. This metallization is provided on all connecting surfaces of ring 5A. This metallization also extends to the inner surface of ring 5A and forms a contact surface, such as that formed by surfaces 50 and 51, for example. These are likewise provided on the outer surface of ring 5A in connection area 6, which is arranged on ring 5B. The connecting conductors 7 and 8 are soldered to the connecting area 6. The frame 5 is fixed to the support 4.

The frame 5 is provided with a cover 9 whose upper level projects above the surface of the plate 3 and the level of the portions where the circuit elements such as 1 and 2 are provided with connecting conductors.

Connecting wire 20 forms the desired electrical connection. In the illustrated example, emitter region 1 of transistor 1
1 is connected on the one hand to the surface 32 and through this surface to the support 4 and on the other hand to the electrodes of the capacitor 2. It is also connected through this surface to the support 4 and, on the other hand, to the electrodes of the capacitor 2. transistor 1
The base region 12 of is connected to the other electrode of the capacitor 2, through which the metallized surface 51 is connected to the base output conductor 8 through another connection. The collector connection between the metallized surface 30 on which the transistor 1 is arranged and the surface 50 connected to the collector output conductor 7 is likewise completed with a connecting conductor.

Board 3 for a better understanding of the method according to the invention
Alternatively, the connection wire 20A connecting the capacitor 2 to the frame 5 is one, and the other connection wire 20 does not protrude outward from the plate 3, so that they can be distinguished by reference numerals.

With particular reference to FIG. 3, the method of manufacturing the above-described assembly under the most advantageous conditions according to the invention will now be described. As described above, the method according to the present invention manufactures the subassembly 60 as a first step, and in this step, circuit elements such as 1 and 2, the plate 3, and the frame 5 are assembled. In this, semiconductor circuit elements 1, 2, etc. are placed on the metallized surface 3 of the plate 3.
0, 31 and connected to at least the connecting conductors 7, 8 by connecting wires 20A, and in a second step this subassembly 60 is connected on the one hand to the support 4 and on the other hand to the cover 9. .

When this subassembly is formed, the first
Then semiconductor circuit elements such as 1 and 2 are soldered to the metallized surfaces 30 and 31 of plate 3. In this case, like all other metallizations, this metallized surface has a layer of gold. The silicon elements designated 1 and 2 are provided with a gold layer on the side to be soldered, so as to form a gold-silicon alloy. The soldering process is performed at a temperature of approximately 380°C. Following this, the plate 3 and frame 5 are placed on a flat work table. The frame 5 is held, for example, in a fixed position, and the plate 3 is held on a flat working table by means of a section system (small drive system), which section maintains the accuracy within the limits applied to the frame and later on it. move it to the side. This allows the two parts, designated 3 and 5, to define their axial positions.

This is followed by a gold connecting wire 20, for example by heat compression.
Connect and provide. In many cases, the structure of the connecting line 20A is strong enough to hold the subassembly 60 during movement from the aforementioned working position to the final assembly process. This assembly process consists of 80% gold and tin.
Performed by 20% alloy. A ring 40 of this alloy is placed between the frame 5 and the cover 9, which have sufficient metallization. A plate 41 of this alloy is placed between the plate 3 and the metallized frame 5 on the one hand and the gold-coated part of the soldering area of the support 4 on the other hand. This assembly is carried out at a temperature of approximately 280° C. in the correct position. At this temperature, the risk of cracks forming in the plate 3 and the risk of damage to this plate and the frame 5 are:
This total envelope is much less than if done at much higher temperatures, as was done in previously known techniques.

In the method of the present invention described above, the mechanical connection characteristics of the subassembly 60 can be achieved not only by the connecting wire 20A, but also by providing a reinforcing wire. A reinforcing wire 21, an example of application in such a case is shown in FIG. 2, mechanically connects the metallized surface of the plate 3 to the other frame surface of the frame 5. That is, for example, as can be seen in FIG.
1, whereby the surface 52 is connected to the insulating surface 33 of the plate 3 and to the above-mentioned surface 31;
Surface 53 is also coupled to insulating surface 34 and surface 31. In this case, line 21 performs no electrical function;
It only performs mechanical action.

[Brief explanation of drawings]

Figure 1 shows the ultra-high frequency semiconductor device shown in Figure 2.
Fig. 2 is a plan view of the device shown in Fig. 1, with the envelope cover removed; Fig. 3 is a sub-assembly including each circuit element, plate, and frame. In order to show the manufacturing state of the assembly, an exploded view of each part of the semiconductor device is shown, and this manufacturing process is a diagram showing the situation before reaching the final manufacturing process of the present invention. 1... Transistor (circuit element), 2... Capacitor (circuit element), 3... Beryllium oxide plate,
5...Frame, 7, 8...Circuit connection conductor, 2
0A, 20...Connection line, 4...Support, 9...Cover.

Claims (1)

[Scope of Claims] 1. A semiconductor device having at least one semiconductor circuit element and a protective envelope, wherein a plate having electrically insulating and heat conducting properties is provided with a metallized surface, and one of the plates is provided with a metallized surface. The semiconductor circuit element is mounted on one side, the board itself is placed on an electrically and thermally conductive support, and the board is surrounded by a frame of electrically insulating material. The frame is provided with the connecting conductors of the circuit, this frame is placed on a support and a cover is provided thereon, i.e. the whole assembly consists of this plate, the support and also the frame and cover which constitute a protective envelope. In the method for assembling a semiconductor device comprising: forming a subassembly 60 comprising the circuit elements 1, 2, the plate 3 and the frame 5 as a first step, the semiconductor circuit elements 1, 2 are attached to the metal of the plate 3; fixed on one of the exposed surfaces 30, 31 and connected it to the connecting wire 2.
0A to at least the connecting conductors 7 and 8, and then as a second step, this subassembly 6
1. A method for assembling a semiconductor device, characterized in that a semiconductor device 0 is connected to a support 4 on one side and to a cover 9 on the other side. 2. A reinforcing wire 21 is provided between the plate 3 and the frame 5 to form a subassembly 60, thereby connecting the metallized surfaces 31, 33, 34, 52, 53 of the plate and the frame to each other. The method according to claim 1.