JP2004181654A - Method for ultrasonic welding of case made of resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for ultrasonic welding of a case made of a resin capable of preventing a circuit part therein from being damaged caused by oscillation during the ultrasonic welding. <P>SOLUTION: The first horn 2 and the second horn 3 ultrasonically oscillated by a high frequency oscillator 1 as an oscillation source are provided on an ultrasonic welding machine, and a phase delay part 5 for delaying a phase by 180 degree is provided between the high frequency oscillator 1 and the second horn 3. Then, a printed circuit board 8 on the central part of which a crystal oscillator 9 is implemented is stored in a pair of cases 6 and 7 made of the resin divided into an upper part and a lower part, and these both cases 6 and 7 are jointed at both facing left and right end parts through the printed circuit board, and these jointed faces are welded by the first and the second horns 2 and 3 ultrasonically oscillated by the phase difference of 180 degree. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic welding method for welding and integrating a pair of resin cases containing a printed circuit board.
[0002]
[Prior art]
Conventionally, in a small memory card manufacturing process called, for example, an SD (Secure Digital) card, a printed circuit board on which various circuit components are mounted is housed in a pair of resin cases divided vertically, and the peripheral edges of both cases The technique of joining and integrating the parts by ultrasonic welding is employed.
[0003]
Conventionally known ultrasonic welding machines include a processing table called an anvil and a horn that ultrasonically vibrates using a high-frequency oscillator as a vibration source, and an appropriate addition is applied to the horn while the workpiece is placed on the processing table. By applying ultrasonic vibration under pressure, the joining surfaces of the workpieces are welded by heat generated by friction or the like (for example, see Non-Patent Document 1). Here, the horn is ultrasonically vibrated at a predetermined frequency using a high-frequency oscillator as a vibration source. Usually, when welding a large workpiece, an ultrasonic welder equipped with a high-frequency oscillator that oscillates at 20 KHz is used. In the case of welding a small workpiece such as a small memory card, an ultrasonic welding machine including a high-frequency oscillator that oscillates at 40 KHz is used.
[0004]
[Non-Patent Document 1]
Toshikazu Sato, “Special Processing”, 1st Edition, Yokendo Co., Ltd., November 20, 1981, p. 141-142
[0005]
[Problems to be solved by the invention]
As described above, in the conventionally known ultrasonic welding methods for resin cases, a printed circuit board is accommodated in a pair of upper and lower resin cases, and the peripheral portions of both cases are set to a predetermined frequency (for example, Since the welding is performed by a horn that vibrates ultrasonically at 40 KHz), the vibration of the horn generated during ultrasonic welding acts on the internal printed circuit board, and the circuit components mounted on the printed circuit board are damaged by this vibration. There was a problem. In particular, when a tuning fork type crystal resonator is mounted on a printed circuit board, the second and third harmonics of the natural frequency of the crystal resonator are close to the vibration frequency (40 KHz) of the horn. There was a problem that the crystal resonator was destroyed due to resonance.
[0006]
The present invention has been made in view of the situation of the prior art as described above, and an object of the present invention is to provide an ultrasonic welding method for a resin case that can prevent damage to internal circuit components due to vibration during ultrasonic welding. It is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above-described object, in the ultrasonic welding method for a resin case according to the present invention, a printed circuit board is accommodated in a pair of upper and lower resin cases, and both the cases are placed via the printed circuit board. While joining at both opposing ends, these joining surfaces were welded by first and second horns that vibrated ultrasonically with a phase difference of 180 degrees.
[0008]
When such a configuration is adopted, when ultrasonically welding the joint surfaces of a pair of resin cases at both ends facing each other through the printed circuit board, vibrations propagating from the first horn toward the second horn and the first Since the vibration propagating from the second horn toward the first horn is canceled at the central portion of the both, the circuit component of the printed circuit board arranged at the central portion is hardly affected by the vibration. Can prevent damage.
[0009]
In the above configuration, as means for ultrasonically vibrating the first and second horns with a phase difference of 180 degrees, a phase delay is provided between one of the first and second horns and the high-frequency oscillator that is the vibration source. It is preferable to interpose a part.
[0010]
Further, in the above configuration, when a tuning fork type crystal resonator is mounted on the printed circuit board, the joint surfaces of both cases are placed with the crystal resonator positioned substantially at the center of the first and second horns. It is preferable to weld, and when such a configuration is adopted, since the external vibration hardly acts on the crystal resonator during ultrasonic welding, the crystal resonator can be reliably prevented from being broken.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an explanatory view showing an ultrasonic welding method for a resin case according to an embodiment of the present invention, and FIG. 2 is a diagram for canceling vibrations generated during ultrasonic welding. It is explanatory drawing which shows operation | movement.
[0012]
As shown in FIG. 1, an ultrasonic welder according to this embodiment includes a high-frequency oscillator 1 that oscillates at a frequency of 40 KHz, and first and second horns 2 that ultrasonically vibrate using the high-frequency oscillator 1 as a vibration source. , 3 and a processing table 4 on which a workpiece is placed, and a phase delay unit 5 is provided between the high frequency oscillator 1 and the second horn 3 to delay the phase by 180 degrees. Yes.
[0013]
The workpiece is a small memory card called an SD card. The small memory card includes a pair of upper and lower resin cases 6 and 7 and a printed circuit board 8 housed in both the cases 6 and 7. And. Various circuit components including a chip resistor, a chip capacitor, and an IC are mounted on the printed circuit board 8, and a tuning fork type crystal resonator 9, which is one of these circuit components, is mounted almost at the center of the printed circuit board 8. Yes.
[0014]
Next, a process of ultrasonic welding the two cases 6 and 7 of the small memory card schematically configured as described above will be described.
[0015]
First, various circuit components including the crystal unit 9 are mounted on the printed circuit board 8, and then the printed circuit board 8 is accommodated in the cases 6 and 7 divided into upper and lower parts. Join with. Next, after placing both the cases 6 and 7 on the processing table 4 of the ultrasonic welding machine, the first horn 2 is pressed right above the joint surface on the left end side in FIG. 1 and the right end in FIG. Ultrasonic vibration is applied to the first and second horns 2 and 3 with the second horn 3 pressed against the joint surface on the side. As a result, the joint surface located directly below the first and second horns 2 and 3 is welded by heat generated by friction or the like, and the left and right ends of both cases 6 and 7 are joined and integrated. At that time, the first and second horns 2 and 3 vibrate at a frequency of 40 KHz using the high frequency oscillator 1 as a vibration source, but a phase delay unit 5 is interposed between the high frequency oscillator 1 and the second horn 3. Therefore, vibrations having a phase difference of 180 degrees are generated from the first and second horns 2 and 3.
[0016]
FIG. 2 schematically shows how the vibration generated at this time propagates through the two cases 6 and 7 which are workpieces, and a region S1 in FIG. 2A corresponds to the first horn 2. Similarly, the region S <b> 2 is a joint surface between the cases 6 and 7 corresponding to the second horn 3 at the joint surface between the cases 6 and 7. Also, the solid line P1 in FIG. 2B indicates the vibration power generated in the first horn 2, and the broken line P2 similarly indicates the vibration power generated in the second horn 3.
[0017]
As is clear from FIG. 2, the vibration P1 generated in the first horn 2 has the largest power in the vicinity of the region S1, and propagates while the power is attenuated from the region S1 to the region S2. On the contrary, the vibration P2 generated in the second horn 3 has the largest power in the vicinity of the region S2, and propagates while the power is attenuated from the region S2 to the region S1. Since the vibrations P1 and P2 generated by the first and second horns 2 and 3 have a phase difference of 180 degrees, the first and second horns are formed in the central portion of the region S1 and the region S2 indicated by the arrow A. The vibrations P1 and P2 generated by the horns 2 and 3 are cancelled. That is, when looking at the printed circuit board 8 housed in both the cases 6 and 7, the vibrations P1 and P2 of the first and second horns 2 and 3 are canceled at the central portion A. The vibration hardly acts on the central portion A. Therefore, when ultrasonic welding is performed on the joint surfaces at both ends of both cases 6 and 7, external vibration hardly acts on the crystal resonator 9 mounted in the central portion A of the printed circuit board 8, and the crystal resonator 9 Destruction can be reliably prevented.
[0018]
It should be noted that ultrasonic welding is not necessarily performed on the remaining joint surfaces (region S3 and region S4 in FIG. 2) of both cases 6 and 7, but ultrasonic welding similar to the above is performed as necessary. Is also possible. Also in this case, since one vibration propagating from the region S3 toward the region S4 and the other vibration propagating from the region S4 toward the region S3 are canceled at the central portion of both, the central portion of the printed circuit board 8 is obtained. External vibration hardly acts on the crystal resonator 9 mounted on the crystal resonator 9, and the crystal resonator 9 can be reliably prevented from being broken.
[0019]
In the above-described embodiment, the printed circuit board 8 having the crystal unit 9 mounted in the center is accommodated in a pair of resin cases 6 and 7 divided into upper and lower parts. Are joined by the first and second horns 2 and 3 that are ultrasonically vibrated with a phase difference of 180 degrees. When ultrasonically welding the joint surfaces of 6 and 7 with the first and second horns 2 and 3, the vibration P 1 propagating from the first horn 2 toward the second horn 3 and the second horn 3 to the second The vibration P2 propagating toward the horn 2 is canceled at the central portion of both, and the crystal resonator 9 mounted on the central portion of the printed circuit board 8 is destroyed due to vibration during ultrasonic welding. Can be reliably prevented.
[0020]
In the above embodiment, the case of ultrasonic welding the both cases 6 and 7 of the small memory card has been described. However, it may be a workpiece in which a printed circuit board is housed in a pair of upper and lower resin cases. For example, the ultrasonic welding method of the resin case according to the present invention can be applied to a workpiece other than the small memory card.
[0021]
In the above embodiment, the case where the tuning fork type crystal resonator 9 is mounted on the central portion of the printed circuit board 8 has been described. However, not only the crystal resonator 9 but also other circuit components, particularly cantilever components, The same effect can be expected when a so-called circuit component is mounted on the central portion of the printed circuit board 8.
[0022]
【The invention's effect】
The present invention is implemented in the form as described above, and has the effects described below.
[0023]
A printed circuit board is housed in a pair of upper and lower divided resin cases, and both cases are bonded to each other at opposite ends via the printed circuit board, and these bonded surfaces are ultrasonically vibrated with a phase difference of 180 degrees. Since welding is performed by the first and second horns, the ultrasonic waves are welded to the opposite ends of both cases through the printed circuit board, so that the propagation from the first horn to the second horn occurs. And the vibration propagating from the second horn toward the first horn are canceled at the center part of both, and the circuit components of the printed circuit board arranged at the center part are damaged due to the vibration at the time of welding. Can be prevented. In particular, when a tuning fork type crystal resonator is mounted at the center of the printed circuit board, external vibration hardly acts on the crystal resonator during ultrasonic welding, so that destruction of the crystal resonator can be reliably prevented.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an ultrasonic welding method for a resin case according to an embodiment of the present invention.
FIG. 2 is an explanatory view showing a canceling operation of vibrations generated during ultrasonic welding.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 High frequency oscillator 2 1st horn 3 2nd horn 4 Processing stand 5 Phase delay parts 6 and 7 Resin case 8 Printed circuit board 9 Crystal oscillator

Claims (3)

A printed circuit board is housed in a pair of upper and lower divided resin cases, and both cases are bonded to each other at opposite ends via the printed circuit board. A method for ultrasonic welding of a resin case, characterized by being welded by first and second horns. 2. The method of ultrasonic welding of a resin case according to claim 1, wherein a phase delay portion is interposed between one of the first and second horns and the high frequency oscillator. 3. The tuning case according to claim 1, wherein a tuning fork type crystal resonator is mounted on the printed circuit board, and the two cases are positioned in the center of the first and second horns. A method for ultrasonic welding of a resin case, characterized in that the joint surface of the resin is welded.

Images