JPS6373613A - Manufacture and welder of chip-type tantalum capacitor - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention provides a method for producing a chip-type tantalum capacitor,
The present invention also relates to a welding device for welding an anode terminal of a chip-type tantalum capacitor to an anode lead terminal of a lead frame.

(Prior art) Chip-type tantalum capacitors are made by mounting chip-type tantalum capacitor elements called pellets (hereinafter also referred to as pellets as appropriate) on a lead frame, welding the anodes together, covering them with a resin mold, and then attaching the leads to the capacitor. Produced by cutting and separating the frame.

Specifically, first, the cathode lead terminal of the lead frame is bent into an L-shape, and a pocket portion is formed at the lower end of the cathode lead terminal. After the conductive adhesive is applied to the pocket, the pellet is loaded into the pocket. Then, a welding current is applied between the anode lead wire led out from the pellet and the anode lead terminal of the lead frame, and the anode lead wire is welded to the anode lead terminal by spot welding using an electrode, for example. , then, together with the lead frame, the outer periphery of the pellet is
Covered with resin mold. Finally, the cathode lead terminal and anode lead terminal of the lead frame are cut and separated to finally produce a chip-type tantalum capacitor.

(Problems with the Prior Art) In the production of the above chip-type tantalum capacitors, the welding process of welding the anode lead wire of the pellet to the anode lead terminal of the lead frame poses a major practical problem.

That is, since the anode lead wire is formed in a state extending from the pellet during the pellet manufacturing process, substances that impede welding are likely to be generated or adhere to the surface of the anode lead wire.

Particularly, in the pellet manufacturing process, an anodic oxide film is formed on the surface of the anode lead wire during the pellet impregnation and firing steps. This anodic oxide film is an insulating film and becomes a significant hindrance during welding.

In addition, in the impregnation and firing process in which a porous tantalum anode body is impregnated with an aqueous manganese nitrate solution and manganese dioxide is generated by thermal decomposition, manganese scatters and adheres to the anode lead wire. However, this impregnation and firing process must be repeated over and over again, and therefore, even under a strictly controlled environment, it is difficult to sufficiently prevent manganese from adhering to the anode lead wire. Manganese adhering to the anode lead wire acts as a foreign substance that increases resistance and becomes an obstacle to welding.

Further, the anode lead wire of the pellet and the anode lead terminal of the lead frame are formed from a combination of materials having greatly different melting temperatures. It goes without saying that if the melting temperatures differ greatly, it is difficult to secure the optimum welding temperature and welding is difficult.In other words, normally the anode lead wire is made of tantalum, and the anode-upper terminal of the lead frame is made of tantalum. , a copper alloy such as nickel silver, 42 alloy, or the like. However, while tantalum has a melting temperature of 299°C, nickel silver has a
1200°C, 42 alloy is 2996°C, which is a big difference. Therefore, during welding, it is difficult to ensure the optimum temperature due to the difference in melting temperature.In other words, it is difficult to maintain heat balance, making welding difficult.

In the actual welding process, spot welding is widely performed in which an anode lead wire and an anode lead terminal are overlapped, sandwiched between upper and lower electrodes, and a high-voltage welding current is passed between the electrodes.

However, as mentioned above, due to the difference in melting temperature, it is difficult to maintain heat balance due to the nature of the wood.In addition, an anodized film, which is an insulating film, is formed on the anode lead wire, and manganese adheres to the anode lead wire. As a result, the resistance of the anode lead wire increases, making it difficult to obtain chip-type tantalum capacitors with stable welding strength, and variations in welding strength result in defective products and a decrease in yield.

”: As shown in the following, the resistance of the anode lead wire increases due to the anodic oxide film and manganese that are formed and attached to the anode lead wire.
increase Therefore, the upper electrode in contact with the anode lead wire is subject to severe wear and must be polished every 500 to 1000 weldings. However, generally known (automatic) welding equipment has a high welding speed of 1 piece/second. It has a welding speed. Therefore, the welding equipment must be stopped every 8 to 16 minutes for maintenance of the upper electrode.

Therefore, the operating rate of the welding equipment decreases, which becomes a major hindrance to mass production. Furthermore, this maintenance becomes an obstacle to labor saving. In other words, the maintenance of the partial electrode is carried out by the worker immediately removing the mandrel after the welding equipment has stopped, polishing it, and then reinstalling it.
It takes a considerable amount of time.

A lot of effort and time are spent on such maintenance, so it is important to save labor on welding equipment.
hindered.

(Object of the Invention) The present invention relates to a production method and welding apparatus for chip-type tantalum capacitors that prevent wear of electrodes and prevent the occurrence of defective products. [Summary of the Invention] To achieve the above object. Furthermore, according to the method for producing a chip-type tantalum capacitor of the present invention, it is noted that the resistance of the anode lead wire increases due to the formation and adhesion of an anodic oxide film and manganese. In other words, before applying welding current between the anode lead wire and the anode lead terminal, a weak check current must be passed between the anode lead wire and the anode lead terminal.
Then, the current value is detected and the suitability of welding is determined. Here, if the resistance of the anode lead wire is large, the detected check current is small, and in such a case, welding is determined to be inappropriate.

If an inappropriate current value for welding is detected, the welding current will not be applied and the welding process will be stopped.

When it is determined that welding is inappropriate, the welding process for the corresponding chip-type tantalum capacitor element is stopped, and the energization check process is similarly performed for the next chip-type tantalum capacitor element. Of course, chip-type tantalum capacitor elements that are not welded are removed, and the occurrence of defective products is reduced.
Prevented before π.

However, by replacing the chip type tantalum capacitor element,
It is preferable to repeat the check process and wait for the welding process. In this way, if the chip-type tantalum capacitor element is replaced until it is determined that welding is possible and the welding process is performed, a so-called missing state can be prevented.

High yield can be ensured.

On the other hand, according to the welding device for a chip-type tantalum capacitor according to the present invention, the anode lead wire and the anode lead terminal are sandwiched between the welding device and the anode lead terminal, and the welding device is disposed below the pair of electrodes. A welding power source is arranged to apply welding current between the electrodes. Furthermore, prior to energization in the welding ITL style, a energization check means is provided to energize a weak check current between the electrodes, detect the current value of the check current, and determine whether or not the energization of the welding radio wave is appropriate. It is arranged.

(Example) An example of the present invention will be described in detail below with reference to one drawing.

First, *to briefly explain, as shown in FIG. 1, in a welding apparatus 10 according to the present invention, a lead frame 12
A chip-type tantalum capacitor element (hereinafter referred to as
14 is a pair of electrodes 16.1
It is sent for 7 hours and welded. However, prior to welding,
The suitability of welding is determined, and the pellets 14 for which welding is determined to be inappropriate are replaced with another pellet by chip-type tantalum capacitor element replacement means 18, and the suitability of welding is determined again. Then, welding current is applied through the electrodes 16 and 17 only to the pellets determined to be weldable, and welding is performed. In addition.

Before this welding process, on the lead frame 12.

The following processing has been performed.

First, as shown in FIG. 2, the lead frame 12 is composed of alternating cathode lead terminals 20, anode lead terminals 22, and tie bars 24 connecting the edges, which are formed to face each other. Additionally, a series of pitch holes 25 are drilled into the edges of the lead frame to feed the lead frame 12 at a predetermined pitch in the direction of the arrow. As shown in FIG. 3, the cathode lead terminal 20 of such a lead frame is bent into an L-shape, and a pocket portion 26 is formed at its lower end. Then, the conductive adhesive 28
It is applied to the pocket portion 26.

On the other hand, the pellet 14 is molded with the outer periphery serving as a cathode 30. Then, the bellet 14 is inserted into the pocket portion 26 of the cathode lead terminal of the lead frame, as shown in FIG.
a and adhered with a conductive adhesive 28. Therefore, the cathode 30 of the pellet is electrically connected to the cathode lead terminal 20 of the lead frame. Further, an anode lead wire 32 extends from the pellet 14 in the direction of the anode lead terminal 22 of the lead frame. Cathode lead terminal 2
When forming the pocket portion 26 by bending the wire, the rising height h is selected such that the anode lead wire 32 comes into contact with the anode lead terminal 22 (see FIG. 5).

As described above, the lead frame I2 and the bellet 14 are
However, in the welding process, the anode lead wire 32 of the pellet is connected to the anode lead terminal 2 of the lead frame.
After welding, the pellet 14 is welded and electrically connected to the resin moldcoat 3. Then, the cathode lead terminal 20 and the anode lead terminal 22 are cut and separated from the lead frame 12, and the extending ends of the cathode lead terminal and anode lead terminal are bent at approximately right angles.
A chip-type tantalum capacitor 34 is obtained (see FIG. 6).

The welding process will be explained in detail below.

As described above, in the semi-finished chip-type tantalum capacitor that has undergone the welding process, a conductive adhesive 28 is applied to the pocket 26 formed at the bent lower end of the cathode lead terminal 20.
is coated. The bellet 14 is then bonded to the pocket portion 26 with a conductive adhesive 28.

Further, the anode lead wire 30 extending from the pellet 14 is
As shown in FIG. 7, the welding device lO is placed above the anode lead terminal 22 of the lead frame and in contact with the anode lead terminal.
The welding power source is connected to the electrodes 16 and 17 by an electric wire 40 and the energization check means is connected to the electrodes 16 and 17 by an electric wire 41, respectively. Note that the electric wire 41 of the energization check means is connected to the anode lead g32. without passing through the electrodes 16.17. It may be directly connected to the anode lead terminal 22.

The electrode I6.17 is supported by a rotating arm (not shown), and by rotating the rotating arm, it is moved and aligned above and below the anode lead wire 32 and the anode lead terminal 22. Then, the upper electrode 12 is lowered and brought into contact with the anode lead wire 32, and the lower electrode 17 is raised and brought into contact with the anode lead terminal 22. and,
The anode lead wire 32 and the anode lead terminal 22 are held between the upper and lower electrodes 16 and 17 while applying a predetermined pressure. Then, the energization check means 38 is activated to apply a low voltage of 3 to 5 cm between both electrodes, and to flow a weak current i for energization check.

Welded portion, ie, anode lead wire 32. Anode lead terminal 2
As can be clearly seen from FIG. 8, which is an enlarged view of FIG.
It flows through a path 42 that reaches the upper terminal 22 and the lower electrode 17.

If an anodic oxide film or manganese is not generated or attached to the anode lead wire 32, or even if it is generated or attached, it is only a small amount, the resistance of the welded portion in the path 42 will not increase. The current drop in path 42 is small;
A preset value, for example, a check voltage of lO~20mA? iti flows via path 42. If the preset check current i is detected by the energization check means 38.

It is determined that the welding is appropriate (possible), the check current i is stopped, and the welding current ■ is changed to the welding chamber IQ36.
From there, it is sent to a path 42 via an electric wire 40. When the welding current I flows through the path 42, 1 exothermic melting occurs, and due to the difference in melting temperature, the anode lead wire 32 sinks into the anode lead terminal 22 and is welded to the anode lead terminal, as shown in FIG. Ru. The welding current application time was set by a timer (not shown) to 8+wm seconds in the example. If the anodic oxide film or manganese is formed or adhered to the anode lead wire 2, or if the resistance of the welded part is large, it is determined that the welding is inappropriate (impossible). In other words, if the check current i shows a value between 2 and 51 degrees, it is considered that the resistance of the welded portion is quite large.

In such a case, if welding chamber fi, ■ is energized,
Sufficient heat generation is not generated in the welding area due to interference from the anodic oxide film and manganese scattering. Therefore, sufficient welding strength cannot be secured. Also, the heat generation may cause local destruction of the anodic oxide film, resulting in local damage. Fever is concentrated. Then, an explosion occurred, and the anode lead wire No. 2 melted and scattered.
There is a risk that the upper electrode 16 will be seriously damaged. Therefore, to ensure proper welding, if the check current is below a predetermined limit, for example below 9 mA, it is deemed inappropriate and no welding takes place. That is, if the detected check current i is below the limit value.

The energization check means 38 issues a signal indicating that welding is inappropriate (welding is not possible). For example, a signal indicating that welding is not possible.

The information is sent to the central processing unit (CPU), and the subsequent opening operation is controlled by the CPU. When this welding impossibility signal is generated, the welding process is immediately stopped. In other words, the scheduled application of welding current from the welding power source 16 or a command from the CPU cancels it. At the same time, the 1-lower electrode 16.17 moves up and down, and the anode lead wire 3
2. They are separated from the anode lead terminals 22, and the electrode rotating arms rotate and return from the aligned position to the initial position. In this way, the bellet 14 is connected to the electrodes 16.17
be freed from.

After the welding process is completed and omitted, the lead frame 12 is automatically moved by 1 pitch, and the next pellet 14 to be welded is sent to a predetermined welding position. Needless to say, it is welded to the anode lead wire 32 or the anode lead terminal 22 through an energization check process and a welding process.

In the energization check process, the pellet I4 determined to be unweldable is automatically or visually inspected by an operator and removed before being coated with the resin mold. for example,
If a biasing means such as a leaf spring is brought into contact with the pellet 14 that has undergone the welding process, the unwelded pellet will be detached from the pocket Z6 despite the adhesive force of the conductive adhesive 28 and automatically be excluded. Of course, even if the welded beret 14 is pressed by a leaf spring or the like, it will not be removed because it has sufficient resistance. However, in the embodiment, the unwelded beret 14 is , configured to be interchangeable with another beret.

In other words, as shown in FIG.
It is equipped with 8. The feeding means 18 is configured to include a chip-type tantalum capacitor element removing means 44, a replenishing means 46 for the conductive adhesive 28, and a supply means 48 for supplying another chip-type tantalum capacitor element. . Then, while the lead frame 12 is stopped, it is removed from the pocket portion 26 at the welding position by the non-weldable bellet 14 or the removal means 44. Then, by means of replenishment means 46, conductive adhesive 28 is
The pocket portion 26 is reapplied. After that, the supply means 4
8, another pellet 15 is supplied and loaded into the pocket 26, and a check current as described above is passed through the path 42 to this new pellet to determine whether welding is possible.

The tantalum capacitor element removing means 44 includes a rotating arm 49 and a pair of clamping chucks 5 at the lower end of the rotating arm.
0, it is rotatable and can be raised and lowered, and is disposed adjacent to the welding position.

In the embodiment, the removing means 44 includes:
It also serves as a part of the supply means. This removing means 44 is
It operates according to instructions from the CPU in response to a signal indicating that welding is not possible. In other words, the signal indicating that welding is not possible is detected by the energization check means 38.
occurs, the CPU detects this and connects the electrodes 16 and 17.
As mentioned above, from the alignment position with the anode lead wire, etc.
Move to the initial position so as not to interfere with the replacement process. Then, the arm 49 of the removing means rotates, and the chuck 50 of the removing means 44 moves above the pellet 14. Then, the removing means 44 is lowered and negative pressure is applied to the chuck 5.
By acting on
The corresponding pellet 14 on 6 is clamped. Thereafter, the removing means 44 ascends, forcibly peels off the pellet 14 from the pocket portion 24, and removes it. Removed beret 14
is dropped into a collection box (not shown) located adjacent to the removal means 44. Note that, in order to facilitate the peeling of the pellet 14, it is preferable to use a slow-acting adhesive as the conductive adhesive 28.

The conductive adhesive replenishment means 46 includes a rotating arm 52 and a conductive adhesive replenishing cylinder 53 attached to the outer end of the rotating arm.
It has a 4R structure and is arranged adjacent to the welding position. The replenishment means 46 sends J! to the removal means 44! [Activated by the movement, the button is placed on the removed pocket portion 26 of the pellet I4,
Apply conductive adhesive 28 again. In other words, Beret 1
4 is removed from the pocket portion 26, the rotating arm 5
2 is rotated, and the refill cylinder 49 is moved onto the pocket portion 26. Then, the conductive adhesive 28 is dripped from the refill cylinder 49 onto the pocket portion 26 and applied.

The chip-type tantalum capacitor element supply means 48 includes a transport means for transporting new pellets 15, a first transport means for transporting the pellets to the transport means, and a second transport means for transporting the pellets from the transport means to the pocket section. and means. In the embodiment, the transport means is formed from a rotary index table 54, and the first transport means is formed from a transport chuck member 55 disposed above the single revolution index table 54 and actuated by negative pressure. . In the embodiment, the removal means 44 or the second transfer means is used, but the transfer chuck member 55 may also be used as the second transfer means, or a separate transfer means may be used as the second transfer means. A chuck member or the like may be provided.

The replacement pellet 15 is, for example, an anode lead wire 3.
2, the rotary index table 54 is held up while being welded to the carrier par 58, and is waiting at a position opposite to the welding position. And the anode lead wire 32'-
A pair of cutters 60 are arranged below.

Note that the structure of the separating means 18 is not limited to the structure of the embodiment, and for example, it can be transferred from the carrier par 58 to the pocket portion 26 without using a conveying means by a transfer chuck member attached to a rotating arm. The pellet 15 may also be transferred directly. Of course, the pellet 15 may not be placed on standby by being welded to the carrier par 58, but may be placed on standby using other methods.

After or during the operation of the replenishment means 46, the supply means 48 configured as described above operates as follows.

Negative pressure is applied to the transfer chuck member 55, and the pellet 15 is held between the pair of chucks. Then, the cutter 60 is operated to separate the pellet 15 from the carrier par. Then, the pellet 15 is transferred from the transfer chuck member 55 to the rotary index table 54. The rotary index table 54 is rotated approximately half a turn,
The pellet 15 is conveyed to a position below the lead frame 12 and adjacent to the pocket portion 26. Then, the second
The removal means 44, which also serves as a transfer means, is operated, and the pellet 15 is transferred from the rotary index table 54 onto the areas 1 to 26 replenished with the conductive adhesive 28, thereby completing the replacement process.

After the replacement step, it goes without saying that the check current i is applied again from the electric wire 41 to the path 40, and it is determined from the detected value whether or not welding is possible.

If the replaced bellet 15 is again determined to be unweldable, the replacement step is repeated until it is determined to be weldable. During replacement, the welding process is interrupted, so if the number of consecutive replacement processes is limited to one or two times, a substantial decrease in the operating rate of the welding equipment 10 can be prevented. However, if only good products are kept on standby as replacement pellets 15, one replacement process is sufficient. Therefore,
Chip-type tantalum capacitors can be mass-produced without reducing operating rates and with high yields.

The outer periphery of the welded pellet 14 determined to be weldable is covered with a resin mold or the like, and the lead terminal 20 is
．． 22 or is cut from the lead frame 12. It goes without saying that the chip-type tantalum capacitor 34 can be obtained by bending and forming the lead terminals 20 and 22.

The above-mentioned embodiments are for illustrating the present invention, and are not intended to limit the present invention in any way, and any modifications, modifications, etc. made within the technical scope of the present invention are also included in the present invention. Needless to say, the present invention is not limited to chip-type tantalum capacitors, but can be applied to other electrical components as necessary.

(Effects of the Invention): As described above, according to the chip-type tantalum capacitor according to the present invention, it is determined whether or not welding is possible through an energization check before welding, and chip-type tantalum capacitors that are determined to be unsuitable for welding are Welding of capacitor elements (vellets) is stopped. In other words, anodized film or manganese,
If it forms or adheres to the anode lead wire, welding will be stopped in advance. Chip-type tantalum capacitor elements whose welding has been stopped will be removed before being covered with the resin mold, preventing the occurrence of defective products in advance. be done.

For chip-type tantalum capacitor elements that have been determined to be unsuitable for welding, it is preferable to replace the chip-type tantalum capacitor element, perform the check process again, and then proceed to the welding process. If the chip-type tantalum capacitor elements are replaced before the welding process is performed, the so-called "out-of-the-way" condition can be prevented and a high yield can be ensured.

In addition, since inappropriate welding is eliminated in advance, -1 part of the electrode wear is suppressed, and the maintenance cycle of the upper electrode is lengthened. Therefore, the operating rate of the welding equipment will be improved, mass production will be possible, and the welding equipment will be more labor-saving and flexible.

Further, according to the welding device for chip-type tantalum capacitors according to the present invention, the above-described production method can be easily carried out, electrode wear is prevented, and the occurrence of defective products can be prevented before JG.

[Brief explanation of the drawing]

FIG. I1 is a partial schematic perspective view of a welding device for a chip-type tantalum capacitor according to this oscillation Iη. Figures 2 and 3 are partial perspective views of the lead frame before and after bending. Figure 4 is a partial perspective view of the chip-type tantalum capacitor before welding, with chip-type tantalum capacitor elements mounted on the lead frame. , Fig. 5 is a cross-sectional view of the chip-type tantalum capacitor along line yV in Fig. 4, Fig. 6 is a perspective view of the chip-type tantalum capacitor as a completed product, and Fig. 7 is a welding power source. , a sectional view of a chip-type tantalum capacitor before welding, similar to FIG. FIG. 2 is an enlarged cutaway view of a type tantalum capacitor. 10: Chip type tantalum capacitor welding equipment, I2:
Lead frame, 14: Chip type tantalum capacitor element (bellet),! 5: Chip-type tantalum capacitor element for differential (bellet), +5: , -1 partial electrode, 17: Lower electrode, 18: Replacement means for chip-type tantalum capacitor element, 20: Cathode lead terminal of lead frame, 22 : Lead frame anode lead terminal, 26:
Pocket portion of cathode lead terminal, 28: Conductive adhesive, 3
0: cathode of chip-type tantalum capacitor element, 32: anode of chip-type tantalum capacitor element, 33: resin mold, 4: chip-type tantalum capacitor, 36: welding power source, 38: energization check means, 42: current path, 4
4: Means for removing chip-type tantalum capacitor element, 46
: Replenishing means for conductive adhesive, 48: Supply means for chip-type tantalum capacitor element, 54 one-rotation index table, 55: Chuck member for transportation, 58: carrier bar, 60: cutter. Figure 2 Figure 3

Claims (4)

[Claims] (1) The process of bending the cathode lead terminal of the lead frame into an almost L-shape and forming a pocket part at the lower end of the cathode lead terminal, and applying a conductive adhesive to the pocket part, and then forming a chip-type tantalum capacitor element. A welding current is applied between the anode lead wire derived from the chip-type tantalum capacitor element and the anode lead terminal of the lead frame, and the anode lead wire is connected to the anode lead by the electrode. A chip-type tantalum capacitor comprising the following steps: welding to a terminal, covering the outer periphery of the chip-type tantalum capacitor element and lead frame with a resin mold, and cutting the cathode lead terminal and anode lead terminal of the lead frame. In this production method, before welding current is passed between the anode lead wire and the anode lead terminal, a weak check current is passed between the anode lead wire and the anode lead terminal, and the current value is detected to determine the welding process. A chip-type tantalum capacitor further comprising an energization check step for determining suitability, and in the energization check step, if an inappropriate current value for welding is detected, no welding current is applied and the welding process is stopped. production method. (2) If an inappropriate current value for welding is detected in the energization check process, remove the chip-type tantalum capacitor element from the pocket of the lead frame, refill the pocket with conductive adhesive, and replace the chip with another chip. 2. The method for producing a chip-type tantalum capacitor according to claim 1, wherein after stacking and bonding the chip-type tantalum capacitor elements in the pocket portion, the energization check step is performed again. (3) In a chip-type tantalum capacitor welding device that welds the anode lead wire of a chip-type tantalum capacitor element bonded with a conductive adhesive onto the cathode lead terminal of the lead frame to the anode lead terminal of the lead frame. , a pair of electrodes arranged above and below to be able to sandwich the anode lead wire and anode lead terminal, a welding power source that passes welding current between the electrodes, and a weak check current that is applied before the welding power source applies the welding current. and detecting the current value of the check current to determine the suitability of welding, and when it is determined that welding is inappropriate, generating a signal indicating that welding is inappropriate and stopping the application of welding current. A chip-type tantalum capacitor welding device characterized by comprising: (4) A chip-type tantalum capacitor element replacement means for replacing a chip-type tantalum capacitor element determined to be unsuitable for welding with another chip-type tantalum capacitor element; A removal means for removing the conductive adhesive from the pocket of the frame, a replenishment means for replenishing the pocket with conductive adhesive, and a supply means for supplying another chip-type tantalum capacitor element and stacking it in the pocket. A welding device for a chip-type tantalum capacitor according to claim 3.