JP3940852B2 - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a glass epoxy board from being mounted afloat, owing to burr without removing the burr of epoxy board by providing a hole for releasing the butt to a position, where the burr is brought into contact with a circuit board when the epoxy board is placed at a predetermined mounting position of the circuit board. SOLUTION: A burr release hole is provided at a position, where an extended burr 91 of a sub-board (glass epoxy board) 11 of a mother board (circuit board) 3 is brought into contact with it. The burr 91 enters the hole. Accordingly, a photodiode unit 1 made of the sub-board 11 with a silicon chip 5 mounted on the circuit board 4 without being afloat.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit board on which glass epoxy substrates are mounted in an overlapping manner.
[0002]
[Prior art]
In the optical rotary encoder for detecting the rotation angle, a silicon chip having a plurality of photodiodes formed on the surface thereof is placed on a glass epoxy substrate (hereinafter referred to as a sub-substrate) that is slightly larger than the chip, and fixed. It may be regarded as a single electronic component (hereinafter referred to as a photodiode unit) and mounted on another circuit board (hereinafter referred to as a motherboard).
An ideal view of this example is shown in FIG. In the photodiode unit 1, a through hole cut at the center is used as an external connection terminal (2 in the figure, hereinafter referred to as an end face through hole terminal 2). A pad 4 of an appropriate size is provided on the mother board 3 side, and the photodiode unit 1 is solder-mounted on the mother board 3 as a surface mount component.
[0003]
A large number of independent photodiodes 6 are provided on the surface of the silicon chip 5 above the photodiode unit 1. Although many optical signals may be handled in this manner depending on the detection method of the rotary encoder, details are not described here. A configuration of a rotary encoder using the mother board 3 is shown in FIG. Between the LED 8 that emits parallel light 81 and the mother board 3, a disk 7 in which a slit 71 is provided in an annular shape is placed and attached to the rotary shaft 17. The LED 8 and the mother board 3 are fixed to the fixed housing 18. A number of photodiodes 6 detect how the slit 71 blocks the light emitted from the LED 8, and the current position of the rotary shaft 17 is determined from these signals.
The LED 8 is arranged so that the parallel light 81 emitted from the LED 8 is perpendicularly incident on the disk 7. Since the mother board 3 is arranged in parallel to the disk 7, it is ideal that the photodiode unit 1 is mounted in close contact with the mother board 3 in parallel. In other words, it is ideal that the distance between each photodiode 6 on the photodiode unit 1 and the disk 7 is made equal to make the detection conditions uniform. This is because the parallel light 81 is rarely a perfect parallel light, and the light diffraction phenomenon by the slit 71 also occurs. Therefore, if the distance from the disk 7 is different, the amplitude and offset value of the detection signal of the photodiode 6 are different. Will change. Since the detection signal is a minute current, it is binarized by the comparator after current / voltage conversion, but if the amplitude and offset value are different, the threshold value of the comparator must be set separately, and the number of circuit components Will increase.
[0004]
However, the bottom (sub-substrate) of the photodiode unit 1 uses a glass epoxy substrate, and has a burr 9 when it is separated from the multi-chip substrate. A multi-chip substrate is shown in FIG. A cut groove 13 is provided by router processing or stamping with a die so that the bridge portion 12 remains between the discard side portion 10 and the sub-substrate 11 to be used. The silicon chip 5 is mounted on the sub-substrate 11 in the state of the multi-piece substrate 14, and the photodiode unit 1 is completed. The method of punching the entire circumference of the sub-substrate without forming the bridge portion 12 cannot be adopted because the silicon chip 5 or a wire bonding line (not shown) may be damaged when the photodiode 6 is taken out from the removed mold.
The completed photodiode unit 1 is separated from the multi-layer substrate 14 with a nipper or the like. At that time, as shown in FIG. 5, burrs 9 inevitably come out from the bottom surface of the photodiode unit 1 to the photodiode unit 1. (The portion that protrudes downward is referred to as the protruding burr 91).
[0005]
[Problems to be solved by the invention]
In order to mount the photodiode unit 1 in parallel and in close contact with the motherboard 3, the protruding burr 91 may be further cut with a nipper or the like, but use a magnifying glass or the like to check for any remaining protrusion. However, work must be performed, workability is poor, and man-hours are extremely high.
However, if it is mounted as it is, the photodiode unit 1 is lifted by the height of the protruding burr 91 and mounted obliquely as shown in FIG. 6, and the distance between each photodiode 6 on the photodiode unit 1 and the disk 7. d _{1 to} d _n are not equal, and a difference occurs in detection conditions of each signal. Further, since the photodiode unit 1 is fixed with the solder 16 in a state of being lifted, it is weak against mechanical strength such as vibration, and is easily dropped from the mother board 3.
[0006]
An object of the present invention is to provide a circuit board for an encoder , which is a mother board, in which a glass epoxy board, which is a sub-board, is prevented from being lifted and mounted without being burred.
[0007]
[Means for Solving the Problems]
A circuit board for the encoder of the present invention, the circuit board of the encoder sub substrate made of a glass epoxy board having a photodiode is mounted on top, the sub-substrate, after the photodiode is fixed, punching The bridge portion formed at the time of processing is cut, and when the sub- board is arranged at a predetermined mounting position of the circuit board, the cut bridge portion is generated in the bridge portion at a position where it hits the circuit board . A through hole is provided to escape the burr.
Therefore, the sub-board made of the glass epoxy board can be mounted on the circuit board without lifting up from the circuit board without removing the burr. In addition, since the conventional circuit board manufacturing technique should just be used to open the hole penetrated in the circuit board, it does not cost much.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front view showing a circuit board mounted state according to an embodiment of the present invention. A burr relief hole 15 penetrating through the burr 91 of the sub-substrate (glass epoxy substrate) 11 of the mother board (circuit board) 3 is provided. The burr 91 is in the burr relief hole 15. Therefore, the photodiode unit 1 composed of the sub-board 11 on which the silicon chip 5 is mounted is mounted on the circuit board 4 without being lifted up.
[0009]
As described above, the present invention eliminates the step of removing burrs by providing burrs for the burrs of the glass epoxy board on the circuit board, so that the glass epoxy board is not lifted and mounted. There is an effect that the glass epoxy substrate can be mounted on the circuit board without reducing the strength and almost no cost .
[Brief description of the drawings]
FIG. 1 is a front view showing a mounted state of a circuit board according to an embodiment of the present invention.
FIG. 2 is a diagram showing an ideal state when the photodiode unit 1 is mounted on the mother board 3;
FIG. 3 is a configuration diagram of a rotary encoder using a mother board 3;
4 is a plan view showing a multi-cavity substrate 14. FIG.
5 is a view showing a burr 9 of the photodiode unit 1. FIG.
6 is a front view showing a state where the photodiode unit 1 with the burr 9 is mounted on the mother board 3. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photodiode unit 2 End surface through-hole terminal 3 Mother board 4 Pad 5 Silicon chip 6 Photodiode 7 Disk 71 Slit 8 LED
81 parallel light 9 burr 91 protruding burr 10 discard side part 11 sub-board 12 bridge part 13 cut groove 14 multi-piece board 15 burr escape hole 16 solder 17 rotating shaft 18 fixed side housing

Claims (1)

In a circuit board for an encoder on which a sub-board made of a glass epoxy board on which a photodiode is mounted is mounted in an overlapping manner,
Bridge the sub substrate, after the photodiode is fixed, which is formed by cutting the bridge portion formed at punching, that the cutting when placing the sub-substrate to a predetermined mounting location of the circuit board a circuit board for an encoder, characterized in that the part is a hole penetrating for releasing burrs generated in the bridge portion at a position which corresponds to the circuit board is provided.

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