JPH07220622A - Bulb provided with base - Google Patents

Abstract

PURPOSE:To relax distortions caused by difference in thermal expansion coefficients between those of an upper end and a metallic base thereby preventing cracks of a tubular glass bulb so as to improve the reliability of a bulb privated with a base by interposing low temperature fusing point glass and soft metal between the end of the tubular glass bulb and the metallic base. CONSTITUTION:In the condition that a lead wire 4 is turned back along the end 2a of a tubular glass bulb 2, the end 2a is covered with low temperature fusing point glass 4 inclusive of the lead wire 4. The inside of one-side metallic base 5 is covered with soft metal 7 easy to melt. Hereby, the end 2a and the metallic base 5 are mechanically and electrically connected to each other by thermal fusion. It is preferably that the above low temperature fusing point glass should be in a system of PbO-B2O3-ZnO. It is preferable that the soft metal should be Sn or Sn-Pb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tube having a tubular glass bulb such as a cold cathode fluorescent lamp and having a metal base attached to its end. More specifically, the present invention relates to a joint between the end and the metal base. It relates to means.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a cold cathode fluorescent lamp 90 showing the structure of a conventional tube of this type, and a lead wire connected to an electrode 92 from both ends 91a of a tubular glass bulb 91. 93 is drawn out, and a metal base 94 made of, for example, brass is adhered to the end portion 91a with a silicone resin 95.

At this time, the lead wire 93 is pulled out through a hole provided in the metal base 94, and is joined to the metal base 94 by soldering on the outside of the metal base 94. Thus, the metal base 94 is mechanically joined to the tubular glass bulb 91 by the silicon resin 95, and electrically joined to the lead wire 93 by soldering.

[0004]

However, in the above-mentioned conventional cold cathode fluorescent lamp 90, first, the end portion 91 is used.
Since a bead stem is used for a and heat welding is performed, and this portion also has a large strain, the end 91a is not attached to the end 91a due to stress at the time of adhesion of the die or stress applied due to subsequent temperature change. There was a problem that a crack was generated to cause a leak.

Secondly, with the above structure, the lead wire 93 also has a metal base 94 at a position extremely close to the end 91a.
Since the solder will be applied to the lead wire 93
Corrosion due to the flux easily reaches the end portion 91a and causes a slow leak, or there is a problem that the end portion 91a is damaged by thermal shock during soldering. Was becoming.

[0006]

As a concrete means for solving the above-mentioned conventional problems, the present invention provides a state in which a lead wire is folded back along an end of a tubular glass bulb.
The end portion is coated with a low melting point glass including the lead wire, and the inner surface of one metal die is coated with an easily fusible soft metal, and the end portion and the die are heat-welded. The present invention is to solve the problem by providing a bulb with a base characterized by being mechanically and electrically joined by.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on an embodiment shown in the drawings. The reference numeral 1 in FIGS. 1 and 2 is a bulb with a base of the present invention shown as an example of a cold cathode fluorescent lamp.
In this cold cathode fluorescent lamp 1, a lead wire 4 connected to an electrode 3 is drawn out from an end 2a of a tubular glass bulb 2, and
Similar to the conventional example, a metal base 5 is attached to the end 2a so as to be electrically connected to the lead wire 4.

Here, in the present invention, the end 2a of the tubular glass bulb 2 and the metal base 5 are the end 2a.
The low melting point glass 6 coated on the side and the easily meltable soft metal 7 coated on the inner surface side of the metal base 5 are joined together, and at the same time, the electrical connection between the lead wire 4 and the metal base 5 is made. It is also supposed to be done.

The above structure will be described in more detail below. First, at the end 2a, the lead wire 4 is folded back along the tube wall of the tubular glass bulb 2 at the end 2a. Then, PbO (lead oxide) -B ₂ O ₃ (boron oxide) -ZnO (zinc oxide) based low-melting glass 6 is coated.

At this time, first, a suspension in which the powder of the low melting point glass 6 is dispersed in a binder solution prepared by adding nitrocellulose to isoamyl acetate at a ratio of 1% is prepared. The two end portions 2a thus formed are respectively dipped to form a coating on the surface of the end portion 2a including the lead wire 4, and one metal die 5 is coated with Sn-Pb alloy by an appropriate means such as hot dip plating. A coating of soft metal 7 (typically solder) is formed.

Then, when joining the two, that is, the end 2a and the metal base 5, the two are put close to each other in an infrared furnace at 400 to 600 ° C.
When the low melting glass 6 coated on a is softened, the metal die 5 is attached to the end portion 2a at a predetermined position. At this time, the soft metal 7 on the side of the metal die 5 in a molten state is melted.
Will fill the gap between them and they will be joined.

Next, the operation and effect of the cold cathode fluorescent lamp 1 of the present invention having the above structure will be described. First,
As a result of a test by the inventor about joining of the end portion 2a and the metal base 5, for example, the atmosphere is exposed from a temperature of 10 ° C. to a high temperature of 300 ° C. for 3 minutes and then immediately immersed in cold water of 20 ° C. Also in the thermal shock test 5
No abnormalities such as peeling off or generation of leaks were observed, and no abnormalities were observed in the tensile test of the metal die 5 of 5 to 6 kg, and it was confirmed to be practically sufficient. Was done.

As described above, the satisfactory joining was obtained because the low-melting glass 6 and the soft metal 7 were interposed between the end 2a and the metal base 5. This is because the low-melting-point glass 6 and the soft metal 7 are both softened or melted in a high temperature range where distortion is particularly likely to occur due to the difference in thermal expansion coefficient with the die 5, and the difference in thermal expansion coefficient between the two is absorbed. Moreover, since the two are joined in the softened or molten state described above, a strong joining strength can be obtained.

Next, the electrical connection between the lead wire 4 and the metal base 5 will be described. According to the structure of the present invention, since the low-melting-point glass 6 which is an insulator is interposed between the lead wire 4 and the metal base 5, it cannot be considered that the electrical connection is made. However, according to the results of experiments by the inventor, it is possible to control the temperature at the time of joining the end portion 2a and the metal base 5 and the thickness of the coating of the low-melting glass 6 as appropriate by controlling the lead. It has been found that it is possible to create conductivity between the wire 4 and the metal base 5.

This condition is that the temperature at the time of joining the end 2a and the metal base 5 is about 600 ° C. and the thickness of the coating of the low melting point glass 6 is several tens of microns or less. It is presumed that the above temperature causes the low melting point glass 6 and the soft metal 7 to be mixed with each other in a part of the surface layer of the low melting point glass 6 to form a conductive portion. The range is 10 microns or less.

Therefore, if the coating of the soft metal 7 is also formed on the lead wire 4 by tin plating or solder plating in advance, the low melting glass 6 mixes the soft metal 7 from both front and back surfaces. Although it is expected that it will occur and the conductivity will be further improved, exactly the same result was obtained even in the result of the experiment by the inventor.

FIG. 3 shows an example of a means for confirming the conductivity between the lead wire 4 and the metal base 5, wherein the lead wire 4 is sufficiently longer than the metal base 5.
The end 2a and the metal base 5 are exposed even after they are joined, and after the joining is performed, the resistance value between the lead wire 4 and the metal base 5 is measured by an ohmmeter RM, and the resistance is measured. It suffices to confirm that the value is equal to or less than the specified value (for example, 0.1Ω).

In summary, according to the present invention, by connecting the end 2a and the metal base 5, the lead wire 4 and the metal base 5 are electrically connected at the same time. Since the end portion 2a and the metal base 5 are interposed by the low melting point glass 6 and the soft metal 7, stress due to temperature or the like does not occur between them, and the lead wire 4 and the metal base 5 are substantially Since no mechanical joining is done,
No stress is generated by both of them.

Although the above embodiment has been described by taking the cold cathode fluorescent lamp 1 as an example, the present invention is not limited to this.
It goes without saying that, for example, in the case of a tube using a tubular glass bulb that is similarly bead-sealed, such as a fuse ball, it can be implemented without any modification.

[0020]

As described above, according to the present invention, the lead wire is folded along the end portion of the tubular glass bulb, and the end portion is covered with the low melting point glass including the lead wire. The inner surface of one metal die is coated with an easily fusible soft metal, and the end portion and the die are mechanically and electrically joined to each other by heat welding to provide a bulb with a die. Therefore, the tubular glass bulb and the metal base are bonded together with the low melting point glass and the soft metal interposed, and the low melting point glass or the soft metal is softened especially at high temperature where distortion is likely to occur, and the difference in the coefficient of thermal expansion is increased. The strain due to the above is alleviated, thereby preventing the occurrence of cracks in the tubular glass bulb, and it is extremely effective in improving the reliability of this type of capped bulb.

Further, according to the present invention, since the lead wire and the metal base are not mechanically directly connected to each other, the distortion due to the joining of the two does not occur, and the use of flux accompanying the connection becomes unnecessary. Therefore, the lead wire is not corroded, and in this respect also, the extremely excellent effect of improving the reliability of the cap-equipped bulb is achieved.

Further, according to the present invention, in the step of joining the tubular glass bulb and the metal base, the lead wire and the metal base can be joined at the same time, so that the production process of the cap-equipped bulb is simplified. It also has an excellent effect in improving productivity.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a bulb with a base according to the present invention in a partially broken state.

FIG. 2 is a sectional view showing a main part of the same embodiment.

FIG. 3 is an explanatory diagram showing an example of an inspection process of the same embodiment.

FIG. 4 is a side view showing a conventional example in a partially broken state.

[Explanation of symbols]

 1 …… Cold cathode fluorescent lamp (bulb with base) 2 …… Tube glass bulb 2a …… End 3 …… Electrode 4 …… Lead wire 5 …… Metal base 6 …… Low melting point glass 7 …… Soft metal

Claims (4)

[Claims] 1. The lead wire is folded along the end of the tubular glass bulb, and the end is covered with a low-melting-point glass including the lead wire, and the inner surface of one metal die is easily covered. A cap-equipped bulb characterized in that a fusible soft metal is coated and the end and the base are mechanically and electrically joined by heat welding. 2. The bulb with a base according to claim 1, wherein the lead wire is covered with the soft metal. 3. The low melting glass is PbO—B ₂ O ₃ —
The tube with a base according to claim 1 or 2, which is a ZnO type. 4. The cap-equipped bulb according to claim 1, wherein the soft metal is Sn or Sn—Pb.