JPH0851265A - Printed circuit board - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object to provide a suitable means for mounting an input circuit of a preamplifier of a television camera in an image pickup tube holder. [Configuration] In configuring the input circuit of the preamplifier,
A through hole is formed on the printed circuit board in accordance with the shape and dimensions of the case of the component, and a conductor pattern for bonding the terminals of the component is provided around the through hole, and the case of the component is covered. It is inserted into the through hole and the terminal is bonded to the conductor pattern. Further, in addition to the first conductor pattern provided on the substrate, a second conductor pattern is formed on the back surface of the substrate.
In addition to the first component, the casing of the second component is inserted into the through hole from the back surface of the substrate, and the terminal is bonded to the second conductor pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a printed circuit board of a preamplifier of a television camera.

[0002]

2. Description of the Related Art In a television camera of an image pickup tube system,
An image pickup tube holder as shown in FIG. 2 is used as a mechanism for optically holding and fixing the image pickup tube in the camera housing. FIG. 3 shows a detailed structure of the image pickup tube holder. As shown in FIG. 3, the target pin 12 of the image pickup tube 9 is
An input circuit 13 of a preamplifier for taking out a signal generated in the photoconductive target 10 to the outside through the target pin 12 is mounted near the. In this portion inside the cap 15, the distance between the face plate 11 of the image pickup tube 9 and the prism 16 is as short as several mm, and the diameter of the image pickup tube holder 8 is three as shown in FIG. It is extremely narrow due to the fact that it cannot be set large due to the mutual positional relationship. The reason for arranging the input circuit of the preamplifier in this part is as follows.

That is, the S / N of the signal of the image pickup tube type television camera is almost determined by the S / N of the preamplifier for detecting the output signal of the image pickup tube. FIG. 4 shows an outline of the preamplifier. As shown in FIG. 4, the preamplifier input terminal 18 has a gate input capacitance Ca of the FET 1 and an output capacitance C of the photoconductive target 10 of the image pickup tube 9.
s, and there is a stray capacitance C ′ generated on the connection between the input terminal 18 and the target pin 12. Where C =
If Ca + Cs + C ', this C and S / of the preamplifier
The relationship with N is generally S / N ∝ I / C …………………………………… (1). Therefore, in order to improve the S / N of the signal of the camera, it is necessary to make the value of C in the above formula (1) as small as possible. Above all, it is important to reduce the stray capacitance C ′. In order to reduce the stray capacitance C ′, the connection between the preamplifier input terminal 18 and the target pin 12 in FIG. 4 must be made as short as possible. Therefore, in the television camera, it is necessary to mount the input circuit 13 of the preamplifier 17 shown in FIG. 4 at a position where the distance from the target pin 12 is the shortest, as shown in FIG.

[0004]

By the way, there is an image pickup tube in which a photoconductive target is applied with a high voltage of several hundreds of volts. In that case, the input circuit of the preamplifier is shown by 13 'in FIG. As described above, the bias resistor Rb and the coupling capacitor Cc are required in addition to the input circuit 13 shown in FIG. In addition, as shown in the input circuit 13 ', FET1
In some cases, a plurality of (normally about two) are connected in parallel to improve the characteristics of the preamplifier such as S / N. As the number of parts used increases, it has become difficult to mount the input circuit 13 of the preamplifier in the narrow space at the tip of the image pickup tube holder 8 shown in FIG. It is an object of the present invention to eliminate the above problems and provide a suitable means for mounting the input circuit of the preamplifier in the image pickup tube holder.

[0005]

In order to achieve the above object, the present invention provides a through hole corresponding to the shape of the outer case of an FET on a printed circuit board which constitutes an input circuit of a preamplifier. A conductive pattern for bonding terminals of the FET is provided around the through holes on both front and back surfaces of the substrate, and the first FET is inserted into the through hole from the front surface of the substrate. , The terminal is bonded to the first conductor pattern provided on the front surface of the substrate, and then the second FET is also inserted into the through hole from the back surface of the substrate, and the terminal is mounted on the back surface of the substrate. It is adapted to be adhered to the provided second conductor pattern. As a result, two FETs can be mounted on the board in a space for one FET, and the total thickness including the mounted FETs can be reduced, so that the board of the input circuit of the preamplifier can be made small, and thus mounting on the pickup tube holder Will be easier.

[0006]

EXAMPLES The present invention will be described below with reference to examples. F as in the preamplifier input circuit 13 'shown in FIG.
In the case of mounting two ETs, conventionally, they were mounted side by side on the board, and thus the area of the board was large and it was difficult to mount them in the image pickup tube holder. (FIG. 5 shows an example of the FET used in the preamplifier.) Therefore, in the present invention, as shown in FIG.
A mounting hole 4 matching the shape of the FET mold (the portion of the body excluding the terminals) is provided on the top, and further copper patterns 3 for connecting the terminals of the FET are provided on both front and back surfaces of the substrate 2, as shown in FIG. The FET 1 is mounted on both sides of the substrate 2 such that the mold is embedded in the mounting hole 4, and each terminal is connected to the copper pattern 3 by the solder 5. As described above, two FETs can be mounted in an area for one FET. Moreover, the total thickness including the height of the parts can be reduced as compared with the case where two FETs are simply mounted one on each of the front and back surfaces of the substrate without using the mounting holes.

[0007]

According to the present invention, in the image pickup tube type television camera, the input circuit board of the preamplifier can be downsized, so that the board can be easily mounted in the image pickup tube holder having a very limited mounting space. Like As a result, the preamplifier input circuit 13 shown in FIG.
Since it can be arranged close to the target pin 12 of, the connection between the input terminal 18 and the target pin 12 can be shortened,
The stray capacitance C ′ generated on this connection can be reduced. Also,
By mounting two FETs vertically on top of each other as shown in FIG. 1, the mounting area becomes 1/2 or less as compared with the case where the FETs are mounted side by side on the same surface as in the conventional case. Stray capacitance (between conductors) can also be reduced. As a result, the S / N ratio of the preamplifier can be improved from the relation of the above-mentioned formula (1), and it can greatly contribute to the improvement of the basic performance of the television camera.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of component mounting on a printed circuit board according to the present invention.

FIG. 2 is a structural diagram showing a mounting state of an image pickup tube holder in a camera housing.

FIG. 3 is a structural diagram showing an example of an image pickup tube holder.

FIG. 4 is a conceptual diagram showing an outline of a preamplifier.

FIG. 5 is a schematic view showing the shape of an FET.

FIG. 6 is a schematic view showing an embodiment of a printed circuit board according to the present invention.

[Explanation of symbols]

 1 FET 2 Printed Circuit Board 3 Copper Pattern 4 Mounting Hole 5 Solder 6 Camera Body 8 Camera Tube Holder 9 Camera Tube 12 Target Pin 13, 13 'Preamplifier Input Circuit

Claims (2)

[Claims] 1. In a printed circuit board on which an electronic component is mounted, a through hole is provided on the substrate in accordance with the shape and size of a casing of the component, and the terminals of the component are bonded around the through hole. The printed circuit board is characterized in that the conductor pattern is provided, the case of the component is inserted into the through hole, and the terminal is adhered to the conductor pattern. 2. In addition to the first conductor pattern provided on the printed circuit board, a second conductor pattern is provided on the back surface of the board, and in addition to the first component, a jacket of the second component is provided. Insert the case into the through hole from the back side of the board,
The printed circuit board according to claim 1, wherein the terminal is bonded to the second conductor pattern.