JP2007234905A - High power amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power amplifier excellent in productivity, and prominent in characteristics as a heat dissipation route and an electric grounding route. <P>SOLUTION: The power amplifier has an FET mounted on a circuit board into a metallic case 5. The FET is contacted with the metallic case 5 by a contact surface 13 through a cover 2, a metallic plate 14 soldered to the cover 2, and silicon grease applied on the metallic plate 14. A grounding wiring is electrically connected on the circuit board through the metallic plate 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  According to the present invention, in an RF high-power amplifier using a field effect transistor (FET), by adding an electric grounding terminal different from the metal flange to the FET, heat dissipation, characteristics as an RF signal transmission line, DC The present invention relates to a high-power amplifier that has a structure that is excellent in all characteristics as a current return path and that is easy to manufacture.

  In RF high-power amplifiers that use high-power field-effect transistors (FETs) that are currently used in mobile phone base station transmitters, the way in which FETs are mounted has a significant impact on the performance and reliability of the device. Yes.

  The FET consumes the most power among the components of the RF high-power amplifier and generates the most heat. Therefore, the FET becomes the hottest component in the device and tends to have a shorter life than other components. Therefore, the lifetime of the FET often determines the lifetime of the entire device.

  In order to extend the life of the FET, it is effective to improve heat dissipation and lower the temperature of the FET. As a method for improving the heat dissipation, a method of increasing the heat sink and increasing the air volume of the fan can be considered, but it has a great influence such as an increase in the size of the device and an increase in manufacturing cost.

  Therefore, attempts have been made to reduce the temperature rise of the FET without greatly affecting the device by optimizing the mounting method of the FET and improving the heat dissipation to the case (heat sink).

The FET used for the RF high-power amplifier has a structure as shown in FIG. 3, and is composed of a terminal 1, a cover 2, a terminal 3, and a metal flange 4. Terminals 1 and 3 are RF signal transmission paths and DC bias current paths. The metal flange 4 serves not only as an electrical ground path for RF and DC signals, but also as a heat dissipation system that releases heat generated inside the semiconductor to the outside.
In general, this is used by being mounted on an apparatus body made of a metal case and a printed circuit board.

There are several possible mounting methods, but each has advantages and disadvantages.
First, as shown in FIG. 4, as the simplest method, the metal flange 4 of the FET is fastened with screws 9 and 10 to be fixed to the metal case 5, and the terminals 1 and 3 are fixed to the surface conductor pattern 6 of the substrate with solder 11 and solder 12. Think about how to solder. In the figure, reference numeral 7 denotes a dielectric portion of the substrate, and reference numeral 8 denotes a conductor pattern on the back surface of the substrate.

  With this method, it is easy to mount an FET. However, the bottom surface of the FET and the surface of the case are not perfectly flat, and there are always curved and fine irregularities, so that the adhesion between the bottom surface of the FET and the contact surface 13 of the case cannot be sufficiently obtained, and the heat dissipation path, Since the characteristics as a path for electrical grounding are not sufficient, it is difficult to use as it is.

  Next, consider a method of soldering and mounting the FET case. In this configuration, the contact surface 13 between the bottom surface of the FET and the case in the configuration shown in FIG. 4 is connected by solder. As an advantage, even if there are curves or fine irregularities on the bottom surface of the FET and the surface of the case, they are compensated by solder, so that the characteristics as a heat dissipation path and an electrical grounding path are excellent. However, in general, the case is extremely large in size and has a large heat capacity, so that it is difficult to solder and the disadvantage is that the manufacturability is poor.

The invention disclosed in Patent Document 1 is also the same, and it is difficult to solder the FET directly to the copper plate of the substrate, and sufficient bonding strength cannot be obtained.
JP 2001-250881 A

  For this reason, in many cases, a cushioning material is often sandwiched between the contact surfaces 13. The advantage of this configuration is that it is easy to manufacture, similar to the configuration shown in FIG. However, in this configuration, the characteristics as the heat dissipation path and the electrical grounding path are affected by the characteristics of the cushioning material.

  Although it is desirable for the buffer material to have low thermal resistance and electrical resistance and to be deformed so as to fill the irregularities on the bottom surface of the FET and the surface of the case, there is no material that completely satisfies these conditions. Silicone grease is often used. Silicone grease has low heat resistance and is easily deformed and thus has excellent heat dissipation properties. However, since it is not a conductor, it adversely affects characteristics as an electrical grounding path.

  As described above, the method of mounting the FET affects not only the heat dissipation but also the electrical characteristics. Therefore, it is difficult to improve the heat dissipation without impairing the electrical performance.

  That is, conventionally, a high-output amplifier that is excellent in manufacturability and excellent in characteristics as a heat dissipation path and an electrical grounding path has not been provided.

  The present invention has been made in view of such problems, and an object thereof is to provide a power amplifier that is excellent in manufacturability and excellent in characteristics as a heat dissipation path and an electrical grounding path.

  In order to achieve the above object, the present invention provides, as a first aspect, a power amplifier in which a field effect transistor mounted on a circuit board is housed in a metal case. The field effect transistor includes a cover and a solder on the cover. It is in contact with the metal case through the attached metal plate and silicone grease applied to the metal plate, and is electrically connected to the ground wiring formed on the circuit board through the metal plate. A characteristic power amplifier is provided.

  In order to achieve the above object, as a second aspect, the present invention provides a power amplifier in which a field effect transistor mounted on a circuit board is housed in a metal case, the field effect transistor comprising: a cover; A power amplifier characterized in that it is in contact with a metal case via a metal plate soldered to a metal sheet and a heat dissipation sheet, and is electrically connected to the ground wiring formed on the circuit board via the metal plate. It is to provide.

  In the first aspect or the second aspect of the present invention, the ground pattern and the metal plate are preferably connected by soldering. In addition, the ground pattern faces the metal case of the circuit board. More preferably, the field effect transistor is electrically connected to the circuit wiring on the side of the circuit board that does not face the metal case.

  In any of the above-described configurations of the first or second aspect of the present invention, the field effect transistor is preferably fixed to the metal case by screwing.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in manufacturability and can provide the power amplifier excellent in the characteristic as a thermal radiation path | route and an electrical grounding path | route.

FIG. 1 shows a configuration of a high-power amplifier according to a preferred embodiment of the present invention.
The FET is the same as the conventional FET shown in FIG. 3 and includes a terminal 1, a metal flange 2, a terminal 3, and a cover 4. An electric grounding metal plate 14 shown in FIG. 2 is soldered to the back surface of the FET.

The metal flange 2 of the FET is fixed to the metal case 5 by tightening screws 9 and 10. The contact surface 13 is coated with silicone grease. The terminals 1 and 3 are soldered to the substrate surface conductor pattern 6 of the substrate using solder 11 and solder 12.
Furthermore, the electrical grounding plate 14 and the substrate back surface conductor pattern 8 are soldered using solder 15 and solder 16.

  In the high-power amplifier having the above configuration, heat generated in the FET is radiated to the metal case 5 through the metal flange 4, the electrical grounding plate 14, and the silicone grease applied to the contact surface 13. Since the metal flange 4 and the electrical grounding plate 14 are soldered, the heat conduction is very good. Moreover, since the thermal conductivity of the silicone grease applied to the contact surface 13 is high, it has sufficient performance as a heat dissipation path as a whole.

  Also, as the electrical grounding path, the substrate backside conductor pattern 8 and the electrical grounding plate 14 are directly soldered, so there is no need to use the contact surface 13 as the electrical grounding path, and silicone grease is used. It is not a problem that it is a nonconductor.

As described above, since the electrical ground path is established by the electrical ground metal plate 14 in the high-power amplifier according to the present embodiment, the electrical ground path is used even though silicone grease is used. Good characteristics.
In addition, since the electrical grounding metal plate 14 is thin, the soldering operation is easier than in the case where the FET is directly soldered to the metal case. This improves the manufacturability of the high-power amplifier.

  That is, in the power amplifier according to the present embodiment, an electrical grounding terminal different from the metal flange is added to the bottom surface of the FET, soldered to the back surface pattern of the printed circuit board, and silicone grease between the bottom surface of the FET and the surface of the case. Is sandwiched between them. The characteristics as an electrical grounding path are extremely good because the electrical grounding terminal is directly soldered, and the heat dissipation is sufficiently good due to the action of silicone grease. Since the printed circuit board has a smaller heat capacity than the case, it is easy to solder and has excellent manufacturability.

In addition, the said embodiment is an example of suitable implementation of this invention, and this invention is not limited to this.
For example, in the above-described embodiment, a configuration in which silicone grease is applied to the contact surface 13 is taken as an example, but a buffer material (for example, a heat dissipation sheet) other than silicone grease may be disposed on the contact surface 13.
In the above embodiment, the configuration in which the electrical grounding metal plate 14 is soldered to the FET is taken as an example, but a component in which these are integrated may be formed and mounted in the same manner as described above.
As described above, the present invention can be variously modified.

It is a figure which shows the structure of the high output amplifier concerning suitable embodiment of this invention. It is a figure which shows the structure of the metal plate for electrical grounding. It is a figure which shows the structure of the conventional high output amplifier. It is a figure which shows the state which fastened the metal flange of FET with the screw | thread and was fixed to the metal case, and soldered the terminal to the surface conductor pattern of the board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 3 Terminal 2 Metal flange 4 Cover 5 Metal case 6 Substrate surface conductor pattern 7 Dielectric 8 Substrate back surface conductor pattern 9, 10 Screw 11, 12 Solder 13 Contact surface 14 Metal plate for electrical grounding

Claims (6)

A power amplifier in which a field effect transistor mounted on a circuit board is housed in a metal case,
The field effect transistor is in contact with the metal case through a cover, a metal plate soldered to the cover, and silicone grease applied to the metal plate,
The power amplifier, wherein the power amplifier is electrically connected to the ground wiring formed on the circuit board via the metal plate. A power amplifier in which a field effect transistor mounted on a circuit board is housed in a metal case,
The field effect transistor is in contact with the metal case through a cover, a metal plate soldered to the cover, and a heat dissipation sheet,
A power amplifier characterized in that it is electrically connected to the ground wiring formed on the circuit board via the metal plate.   3. The power amplifier according to claim 1, wherein the ground pattern and the metal plate are connected by soldering.   4. The power amplifier according to claim 3, wherein the ground pattern is formed on a surface of the circuit board facing the metal case.   5. The power amplifier according to claim 4, wherein the field effect transistor is electrically connected to a circuit wiring on a surface of the circuit board on a side not facing the metal case.   6. The power amplifier according to claim 1, wherein the field effect transistor is fixed to the metal case by screwing.

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