JPS59189534A - Method for sealing off vacuum display device - Google Patents

Abstract

PURPOSE:To make it possible to seal off the vacuum display device with solder in its working range to develop slow evaporation and emit little gas, by disposing solder carried by a conductive ribbon at the evacuation hole in such a manner that the solder will plug the evacuation hole, pressing the ribbon from above, applying an electric current to the ribbon to heat the solder and, at the same time, applying supersonic vibration to the solder, so that the solder is allowed to adhere to the sealing portion only interfacially at the temperature under its melting point. CONSTITUTION:A conductive ribbon 16 with solder 15 of In or Zn soft solder in a ring form soldered thereto and the tip of a supersonic horn 17 as kept in contact with each other is held coaxially with the evacuation hole 10 of the vacuum display device 11 to oppose the same, and the horn 17 is lowered in the direction as indicated by the arrow, whereby the solder 15 is pressed against the display portion 11. In this state, an electric current is applied to the conductive ribbon 16 from a power source 18, whereby the solder 15 is heated to the temperature just below its melting point. At the same time as this heating, ultrasonic vibration is applied to the horn 17 for a predetermined period of time by passing a high frequency current through a transducer. By such operation, the solder 15 is allowed to adhere to the circumferential surface of the evacuation hole 10 of the display device 11 at the temperature just below the melting point of the solder 15 and the display device 11 is sealed off with its interior kept at high vacuum.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to display devices such as fluorescent display tubes (VFD) and plasma displays (FDP), so-called vacuum displays equipped with a container hermetically sealed in a high vacuum. This relates to a method for manufacturing a vacuum display device, and in particular to a method for sealing a vacuum display device, which is suitable for sealing by providing an exhaust hole that does not protrude in a part of the container, and introducing exhaust or gas through the exhaust hole. It is.

[Prior art]

Conventionally, when manufacturing vacuum display devices such as VFDs and FDPs, a container is formed by sealing an assembled glass substrate and a face glass, and a part of the container is attached to a high vacuum. A method is used in which the container is hermetically sealed to a high vacuum by evacuating or introducing gas through a capillary tube (hereinafter referred to as an exhaust pipe) into which a specified gas is introduced after creating a high vacuum. It is being

However, with this side stop method, the inside of the container must be kept in a high vacuum, the exhaust pipe used to introduce the gas must be specially installed using a material different from that of the display device container, and the tip-off must be performed after a certain process is completed. Because the exhaust pipe must be sealed and cut by heating, for example, it is not possible to cut it from the base of the exhaust pipe, and the remaining part of the exhaust pipe protrudes from the finished display device. It will remain. Therefore, such conventional sealing methods have the following drawbacks.

1) The exhaust pipe has a small diameter and is long due to the convenience of connection with the device and the need for tip-off, so the conductance during exhaust is small.

11) Since the tip of the exhaust pipe after tip-off is structurally fragile, its strength is problematic in handling.

111) When mounting inside each device, the remaining part of the exhaust pipe must be a protrusion, which becomes an obstacle to increasing the mounting density. Therefore, at present, the exhaust pipe mounting position must be specified by the user depending on the product, making it difficult to standardize. Additionally, this changes the posture of the product when the exhaust pipe is connected to the exhaust device, causing problems such as temperature distribution during baking and breakage of the exhaust pipe due to its own weight.

iv) A special connection structure that does not cause vacuum leaks and can withstand baking temperatures is required to connect the exhaust pipe and the exhaust device.

Another conventional method is to provide a protruding exhaust hole in a part of a PDP or a container that is hermetically sealed in a high vacuum for manufacturing, and after exhausting through the exhaust hole, gas is introduced to reduce the A method of sealing with a melting point solder material has also been proposed. This method can eliminate the drawbacks of items 1) to iv) above because it can be sealed without using an exhaust pipe, but it has the following problems.

Firstly, the entire low melting point solder is heated above the melting point or glass working temperature and sealed depending on the applied pressure and wettability, so the impurity gas is added to the plasma gas composition by gas release from the solder. Contamination cannot be avoided and may adversely affect characteristics such as discharge starting voltage and color tone. Also,
The second drawback is the problem of the vapor pressure of the solder material. In other words, low melting point materials generally have a high vapor pressure, and when melted at low pressure, spackle occurs, and contamination within the display device can easily cause insulation failure, especially in the case of VFDs that are sealed in high vacuum. Difficult to apply (in the case of VFD,
phosphor or cathode contamination).

Furthermore, the third drawback is that due to the second problem described above, contamination occurs on the inner wall of a chamber such as an exhaust device, and it is difficult to obtain a clean vacuum due to gas adsorption and release of this sputtered material. Therefore, even in FDP, the presence of impure gas becomes a problem when introducing gas. Therefore, it becomes necessary to clean the inside of the chamber after every certain process. The fourth drawback is that when processing is performed by installing a heating element for melting the solder in the chamber in a vacuum furnace, its thermal efficiency deteriorates, and a large amount of heat is also transferred to the chamber side. , the third problem described above is likely to be further exacerbated.

[Summary of the invention]

The present invention has been made in view of the above points and in order to eliminate such drawbacks of the conventional technology.
After exhausting the air through this exhaust hole, when sealing the exhaust hole, the sulter is sandwiched between energized ribbons so as to close the exhaust hole, and pressure is applied from above the energized ribbon to apply ultrasonic vibrations. By applying electricity to the ribbon to preheat the solder and sealing the solder at a temperature just below its melting point, spatter and outgassing from the solder can be reduced even in high vacuum, and it can also be used in areas with low evaporation rates and low outgassing. The present invention provides a sealing method that enables sealing. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

〔Example〕
.

FIG. 4 is a schematic diagram for explaining an embodiment of the method for sealing a vacuum indicator according to the present invention. The case where it is applied to a VFD to be sealed will be shown, and the process will be explained in detail.

First, a display section 2 and a grid 3 on a glass substrate 1. An exhaust hole 10 for exhaust (exhaust and gas introduction in the case of PDP) is provided at the end of the area of the cathode 4 excluding the electrode part and the drive lead lead-out part (not shown), and the substrate 1 and the cover glass A vacuum display 11 as a display device is assembled in advance by sealing 5 in an atmospheric furnace to form an airtight container 6. Next, this vacuum indicator 11 is placed on a heating pedestal 14 in which a baking heater is embedded in a chamber 13 which is configured to be evacuated by a vacuum evacuation device 12 (in the case of a PDP, exhaust and gas introduction).
Place it on. This means that when heating and degassing the vacuum indicator 11, heat conduction is actively used to avoid heating the chamber 13, etc., which is not related to the process, and to suppress the gas released from the chamber 13 so that the high vacuum Helpful to get.

Needless to say, connect the current-carrying terminal for disassembling the cathode.

Next, the evacuation device 12 is activated to evacuate the chamber 13 through the exhaust hole 10 of the vacuum indicator 11, thereby performing a predetermined evacuation process. In the case of a PDP, baking, gas introduction, etc. are performed in the exhaust process. Next, a current-carrying ribbon 16 is soldered in a ring shape with solder 15 made of indium (In) or zinc (Zn)-based solder in advance.
As shown in FIG. 1, the tip of the ultrasonic horn 17 is brought into contact with the exhaust hole 10 of the vacuum indicator 11 on the same axis, and the horn 17 is lowered in the direction of the arrow. The vacuum display section 11 is pressurized. In this state, a current is applied from the power supply 18 to the current-carrying ribbon 16 to energize it, heating it to a temperature just below the melting point of the solder 15. At the same time as this heating, a high frequency current is passed from an ultrasonic transmitter (not shown) to the transducer to apply ultrasonic vibration to the horn 17 for a certain period of time.

Through the above operations, ultrasonic vibration is applied in the chamber 13, and at the same time, electricity is applied to the current-carrying ribbon 16 to connect the solder 15.
By preheating the solder 15 and adhering the solder 15 to the circumferential surface of the exhaust hole 10 of the vacuum indicator 11 at a temperature just below the melting point, the inside of the vacuum indicator 11 is hermetically sealed to a high vacuum, and the seal is not cut. Complete. Thereafter, the vacuum indicator 11 is taken out from the chamber 13, and the unnecessary part of the energized ribbon 16 is cut off by repeatedly bending the ribbon 16, as shown in FIG.
A finished product in which the exhaust hole 10 is sealed can be obtained in step a.

In order to facilitate the bending of the current-carrying ribbon 16, the ribbon 16 is not-fetched on both sides of the ring-shaped solder 15 in the width direction, as shown in FIGS. 3(a) and (1). It is preferable to provide a slotted portion 20 or a long hole portion 21 as shown in FIGS. 4(-) and 4(b). Also, this means that after the seal is cut off, the power supply 18
It is also possible to burn out this part by passing a larger current through it.

Further, the solder 15 used in the present invention may be any material that can be bonded to glass or ceramic as a substrate without metallization, such as a low melting point metal such as In or its alloy, or Zn-based solder. In addition, the shape of the solder 15 is the minimum amount required to seal the exhaust hole 10 of the vacuum indicator 11, that is, by applying it in a ring shape, spatter can be minimized even if the solder exceeds its melting point. . Also,
The solder 15 does not necessarily have to be solder-plated on the current-carrying ribbon 16, but the purpose can also be achieved by sandwiching an independent component as a solder or attaching it in advance to the board side.

Further, in the above-mentioned embodiment, the exhaust hole 10 is provided in the substrate 1 constituting the container 6 of the vacuum indicator 11 and the exhaust hole 10 is sealed. An exhaust hole (not shown) is provided at the end of the glass 5 that constitutes the container 6, and a ring-shaped solder 15 is sandwiched between conductive ribbons 16 so as to close the exhaust hole. By applying pressure from above to apply ultrasonic vibrations and at the same time preheating the solder 15 by applying electricity to the ribbon 16, it is possible to seal and cut at a temperature just below the melting point of the solder 15. In FIG. 5, the same or equivalent parts as in FIG. 1 are given the same reference numerals.

〔Effect of the invention〕

As explained above, according to the sealing method according to the present invention, since the solder is sandwiched between the container body and the current-carrying ribbon during sealing, spatter and released gas are reduced. Moreover, since the solder uses a combination of electrical heating using a ribbon and ultrasonic vibration to bond only the interface at a temperature below the melting point, spatter and emitted gas can be further reduced. In addition, since the solder is preheated by energizing the ribbon, thermal efficiency is better than when radiation is used in a vacuum furnace, and there is no heating of the chamber, etc., and there is no risk of excess gas being released. In addition, the current-carrying ribbon is made of 426 alloy, has a thermal expansion coefficient similar to that of the container substrate, and is sealed in a sandwich structure, making it easier to withstand thermal shock even if the solder has a slightly different thermal expansion coefficient. Furthermore, there are excellent effects such as eliminating fragile protrusions and increasing conductance during exhaust.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining an embodiment of the sealing method according to the present invention, FIG. 2 is a partially cutaway sectional view of a completed device obtained by the above embodiment, and FIG. 3(a). (b) and FIGS. 4(a) and (b) are side sectional views and bottom views showing modified examples of the current-carrying ribbon, respectively, and FIG. FIG. 2 is a main safety front view and a side view thereof. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Display part, 5... Cover glass, 6... Container, 10... Exhaust hole, 11...
... Vacuum indicator, 12... Vacuum exhaust device, 13.
...Chamber, 14...Heating stand, 15...
・Ring-shaped solder, 16... Current-carrying ribbon, 11
...Ultrasonic horn. Patent applicant: Ise Electronics Industry Co., Ltd. Agent: Masaki Yamakawa (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 (G) Figure 5 (b) 2

Claims (4)

[Claims] (1) In a vacuum indicator equipped with a container that is hermetically sealed in a high vacuum, when exhausting air through a non-protruding exhaust hole provided in a part of the container and then sealing the exhaust hole, The solder is sandwiched between energized ribbons so as to block the solder, and the energized ribbons are pressurized from above to apply ultrasonic vibrations, and at the same time, the ribbons are energized to preheat the solder, thereby heating the solder to its melting point. 1. A method for sealing a vacuum display device, characterized in that the ribbon is sealed at a temperature just before that, and then unnecessary parts of the ribbon are cut off. (2) The vacuum display according to claim 1, characterized in that the exhaust hole provided in a part of the container is formed in an area where there is no display part and drive lead lead-out part to perform sealing. How to seal the container. (3) The method for sealing a vacuum indicator according to claim 1, wherein the current-carrying ribbon is provided with either a recessed portion or a hole to facilitate cutting off unnecessary portions thereof. (4) The vacuum indicator according to claim 1 or 3, characterized in that the sorter is formed into a ring shape and solder-plated on a current-carrying ribbon in order to minimize spatter and gas release. Sealing method.