WO2005064628A1

WO2005064628A1 - Tab terminal for electrolytic capacitor

Info

Publication number: WO2005064628A1
Application number: PCT/JP2004/008756
Authority: WO
Inventors: Futoshi Ishii; Shuhei Yoshizawa; Hiroyuki Fujinaka
Original assignee: Kohoku Kogyo Co., Ltd.
Priority date: 2003-12-25
Filing date: 2004-06-22
Publication date: 2005-07-14
Also published as: CN1751368A; CN1751368B; KR100702607B1; KR20060005290A; MY140340A

Abstract

Even when a lead wire plated with lead-free tin and available from a wire manufacturer is directly used as a tab terminal, it is possible to obtain a tab terminal in which tin whisker is not generated from a welded part and which exhibits good solder wettability. Its producing process is also disclosed. The tab terminal for an electrolytic capacitor is obtained by welding an aluminium core having a flat press part to the end part of a lead wire having a metal layer of tin formed on the surface of the core. The surface at the welded part between the lead wire part and the aluminium core is subjected to a treatment for suppressing growth of whisker.

Description

Specification

Tab terminal for electrolytic capacitor

Technical field

The present invention relates to a tab terminal used for an electrolytic capacitor, and more particularly, to a tab terminal provided with a lead-free tin plating, and a method for manufacturing the same.

Background art

[0002] An electrolytic capacitor is formed by winding an anode electrode foil and a cathode electrode foil made of a valve metal such as tantalum or aluminum through a separator to form a capacitor element. It is manufactured by holding it and storing it in an outer case. The anode electrode foil and the cathode electrode foil are joined by a known means such as stitch bonding or ultrasonic welding for connecting the respective electrodes to the outside.

[0003] The tab terminal is composed of three parts: a flat part, a round bar part, and a lead wire part. The flat part is the part that is joined to the electrode foil, the round bar part is the part that is inserted through the sealing body that seals the outer case, and the lead wire part is the lead part that is mounted on the circuit board. Yes, a flexible lead wire is used to ensure ease of handling during mounting.

[0004] Such a tab terminal having three partial forces is usually produced by welding two types of members. That is, a flat portion and a round bar portion are formed using a core wire made of an aluminum material or the like, and a lead wire is welded to the round bar portion. In addition, since the electrolytic capacitor is mounted on the circuit board using solder, in order to improve the soldering characteristics, a lead wire whose surface is tinned with tin-lead containing tin is used.

[0005] In recent years, in consideration of the environment, lead-free soldering has been started for lead-free electrode terminals of electronic components and for joining electronic components. For lead wires used as electronic components, lead-free tin balls, so-called lead-free tin balls, are beginning to be used instead of conventional lead-containing tin balls. In such a tab terminal using a lead wire provided with a lead-free tin plating, there was a problem that tin dies were generated at a welding portion between the aluminum round bar portion and the lead wire portion. Since this tin force grows over time, the whisker Even after removing, the power gradually grows thereafter. Therefore, after mounting the electrolytic capacitor on the circuit board, the force generated from the lead wire on the anode side and the whisker generated from the lead wire on the cathode side are bonded to each other, or the force generated on the lead wire portion is reduced. The leakage current of the electrolytic capacitor may reach the surface of the circuit board, and a short circuit may occur.

[0006] In order to suppress the generation of tin-ice force from a welded portion in order to solve such a problem, Japanese Patent Application Laid-Open No. 2000-12386 discloses 0.5-10 Owt% of a metal such as bismuth. The use of a lead provided with a metal layer made of tin is disclosed. By adding a metal such as bismuth to tin, the generation of a zinc force can be suppressed.

[0007] However, in order to provide a metal layer made of tin containing bismuth on the surface of the lead wire, it is necessary to apply tin alloy containing a predetermined amount of bismuth. Therefore, lead-free tin-plated lead wires available from wire manufacturers cannot be used directly for the production of tab terminals, and a separate plating step is required. As described above, if the tab terminal can be manufactured by using the lead wire available from a wire manufacturer or the like as it is, the manufacturing process does not become complicated and the manufacturing cost does not increase.

[0008] In addition, while the portion where the force is generated is only the welded portion between the aluminum core wire and the lead wire, bismuth / tin alloy plating is applied to the entire lead wire, so that the portion where no whisker is generated is formed. The plating process is wasted, resulting in an increase in cost.

[0009] Further, when the content of bismuth added to tin increases, plating characteristics such as solder wettability change.

Disclosure of the invention

[0010] The present inventors have now found that formation of tin oxide on the surface of a tinned lead wire can suppress the generation of a force that does not impair solder wettability. The present invention is based on strong knowledge.

[0011] Accordingly, an object of the present invention is to generate a tin-based force from a welded portion even when a lead-free tin-plated lead wire available from a wire material manufacturer or the like is used as it is for a tab terminal. An object of the present invention is to provide a tab terminal that does not perform soldering and has good solder wettability, and a method of manufacturing the same. [0012] A tab terminal for an electrolytic capacitor according to the present invention is for an electrolytic capacitor in which an aluminum core wire having a pressed portion is welded to a lead wire end in which a metal layer made of tin is formed on the surface of a core material. A tab terminal, wherein a surface of a welded portion between the lead wire portion and the aluminum core wire is subjected to a die force growth suppressing process. In this way, by performing the whisker generation suppression process on the surface of the welded portion between the aluminum core wire and the lead wire, which is the place where the die force is generated, the tin die force is prevented from growing over time from the welded portion. be able to.

[0013] As a preferred embodiment of the present invention, the whisker suppression treatment is a tin oxide formation treatment. The tin formed on the surface of the weld is oxidized to at least SnO or SnO.

By changing to 2, the whiskers generated from the welded portion can be effectively suppressed.

Further, the tin oxide forming treatment is preferably performed by a heat treatment of the tab terminal. The heat treatment temperature is preferably in a range of 60 ° C. to 180 ° C., particularly 80 ° C. to 150 ° C. More preferred Les ,. The tab terminal is heat-treated in an oxygen atmosphere in such a temperature range, and tin oxide is formed on the surface of the tin plate, thereby obtaining a tab terminal with reduced power generation without impairing the solder wettability of the tab terminal. be able to.

[0015] Further, the tin oxide forming treatment can also be performed by a solvent treatment. By performing the tin oxide formation by solvent treatment, it is possible to selectively perform the whisker generation suppression treatment only on the portion of the tab terminal that requires the whisker generation treatment.

[0016] The solvent is preferably an aqueous solution of an inorganic acid salt selected from the group consisting of silicates, borates, phosphates, and sulfates, and an aqueous solution further containing an ammonium salt. It is preferable that By performing solvent treatment using such an aqueous solution, tin oxide can be formed on the tin surface to the extent that solder wettability is not impaired, and the effect of suppressing whisker generation can be obtained.

[0017] The whisker suppression treatment using a solvent can also be performed in combination with the above heat treatment. By performing the heat treatment and the solvent treatment in this manner, a further whisker suppression effect can be obtained.

[0018] As another aspect of the present invention, a method of manufacturing a tab terminal for an electrolytic capacitor according to the present invention comprises: A step of welding a lumi-core wire and a step of applying and attaching a solvent to the welded portion immediately after welding.

Further, as another aspect, the method for manufacturing a tab terminal for an electrolytic capacitor according to the present invention provides an aluminum capacitor having a pressing portion at an end of a lead wire having a metal layer made of tin formed on a surface of a core material. A step of preparing a tab terminal by welding a core wire; and a step of heat-treating the welded tab terminal.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a tab terminal and a method for manufacturing the same according to an embodiment of the present invention will be described.

The tab terminal for an electrolytic capacitor of the present invention has a structure in which an aluminum core wire having a pressed portion is welded to a lead wire end in which a metal layer made of tin is formed on the surface of a core material. The welding between the wire and the aluminum core wire has been subjected to a growth control process for steel force. The lead wire that constitutes the tab terminal of the present invention is provided with a tin plate, and a normal manufacturing method can be used in a manufacturing process until the tin plate is provided. In addition, as the lead wire, a commercially available lead-free tinted CP wire (lead wire) or the like can be used.

The thickness and length of the lead wire are not particularly limited, and various CP wires can be used according to the required characteristics of the electrolytic capacitor. Note that, as the CP wire, an iron core Z copper sheath type is usually used from the viewpoint of conductive properties.

[0022] As the aluminum core wire constituting the tab terminal of the present invention, those used for conventional tab terminals can be used, and commercially available ones can be used.

The aluminum core wire functions as an electrode of an electrolytic capacitor, and one end of the aluminum core wire has a flattened shape. The pressing portion can be formed by a conventional technique. For example, by pressing an aluminum core wire and cutting it into a predetermined shape, an aluminum core wire having a compressed portion having a predetermined shape can be manufactured. The step of cutting the pressed portion into a predetermined shape can be performed simultaneously with the press working.

[0024] The lead wire and the aluminum core wire can be joined by a conventional method to form a tab terminal. For example, both ends of the aluminum core wire and the lead wire can be joined by melting and joining both ends of the aluminum core wire and the lead wire by spark discharge or the like. The tab made in this way The tab terminal of the present invention can be manufactured by performing a whisker growth suppression treatment on the welded portion between the aluminum core wire and the lead wire of the terminal.

[0025] The present inventors have confirmed that the die force generated near the welded portion of the tab terminal is composed of tin metal alone. And, it has been found that whiskers generated over time can be suppressed by converting tin existing in the welded portion into tin oxide in advance. In other words, the present invention has been derived as a result of intensive studies on the relationship between the tab terminal processing method and the occurrence of whiskers, focusing on the cause of whisker generation.

[0026] According to the findings of the present inventors, the tin dicing force is composed of a simple metal made of tin, and it is estimated that the tin dicing force is derived from a tin plate provided on the surface of the lead wire. The force is generated only at the welded portion between the lead wire and the aluminum core wire where no force is generated. The reason is considered as follows. That is, at the joint, metals such as aluminum, copper, and tin solidify while the residual stress during welding remains. Tin, unlike aluminum and copper, has a low melting point (232 ° C) and can undergo crystal transformation at low temperatures (tens of degrees C). In the state where such residual stress (strain) remains, it is presumed that the tin crystal transformation proceeds even at room temperature and turns into needle-like whiskers, which appear from the welded portion.

[0027] It should be noted that the whisker removal performed immediately after the production of the tab terminal does not provide a fundamental solution since the growth of the tin die force gradually progresses in the order of several months. That is, according to the findings of the present inventors, it is necessary to suppress the growth of the power itself.

[0028] In the present invention, in order to suppress the crystal growth of tin, residual stress in the welded portion is removed, and tin is transformed into tin oxide, and as a result, the generation of whis force is suppressed. is there. It was unexpected that the modification of tin in the welded portion to tin oxide does not cause tin crystal transformation and effectively suppresses tin crystal growth.

[0029] In the present invention, tin in the welded portion of the tab terminal is oxidized by heat-treating the tab terminal in an oxygen atmosphere in a temperature range of 60 to 180 ° C, and tin oxide is formed on the surface of the tin plate. To form. The heat treatment is performed after manufacturing the tab terminals (after welding the aluminum core wire and the lead wire). Prior to welding, heat-treat only the tinned lead wire, and then Welding force It is preferable to perform heat treatment after welding to form a tab terminal. By performing whisker generation suppression treatment after welding, tin that appears on the surface of the welded portion can be efficiently oxidized. If the heat treatment is performed at a temperature lower than 60 ° C, the effect of suppressing the generation of the dysforce cannot be sufficiently obtained. On the other hand, in order to oxidize tin, it is preferable to perform heat treatment at a high temperature.However, at temperatures exceeding 180 ° C, tin oxidation proceeds too much, and the surface of the lead wire becomes discolored and solder wettability decreases. . That is, by heat treatment in an oxygen atmosphere, part of the metallic tin existing near the surface of the welded part is converted to tin oxide (SnO or Sn〇).

2

) Is important. Although the presence of tin oxide is preferred for the purpose of suppressing the generation of whiskers, if all of the metallic tin is oxidized to tin oxide, the solder wettability is undesirably reduced. In the tab terminal of the present invention, it is preferable that metal tin and tin oxide are present at an appropriate ratio. As such a heat treatment temperature at which metal tin and tin oxide can be present at an appropriate ratio, a temperature range of 80 to 150 ° C. is particularly preferable. The heat treatment time is preferably in the range of 10 to 60 minutes, and particularly preferably in the range of 15 to 30 minutes. If the heat treatment temperature exceeds 60 minutes, tin oxidation proceeds too much, which has an adverse effect on solder wettability.

[0030] In the tab terminal for an electrolytic capacitor according to the present invention, since the strain remaining in the welded portion is also reduced by the heat treatment, whisker generation can be further suppressed. The heat treatment can be performed by a conventionally used method, and is not particularly limited.

[0031] In another preferred embodiment of the present invention, the whisker generation suppression treatment described above can be performed by a solvent treatment. Solvent treatment can form tin oxide only on the welded part of the tab terminal.

[0032] The tin oxide can be formed by applying an aqueous solution of an inorganic acid or immersing the tab terminal in an aqueous solution of an inorganic acid after the tab terminal is manufactured. Immediately after welding the aluminum core wire and the lead wire during the tab terminal manufacturing process, it is preferable to apply and attach an aqueous solution of an inorganic acid to the welded portion. Since the tin force is generated immediately after welding of the terminal and grows gradually, solvent treatment is applied when the whis force is still generated and no whis force is generated, effectively suppressing the generation of the sui force. it can. Note that “immediately after welding” means several milliseconds to 11 seconds after welding. In the present invention, it is preferable to apply the solvent within 500 milliseconds, preferably within 300 milliseconds after welding.

In another preferred embodiment of the present invention, it is preferable to further apply a solvent when cleaning the tab terminals.

[0034] In the solvent treatment, the temperature of the welded portion is preferably 80 to 250 ° C, more preferably 85 to 185 ° C. As described above, by applying the solvent when the welded portion is at a certain high temperature, the formation of tin oxide is promoted, whereby the generation of the die force can be suppressed effectively. The above temperature can be achieved by applying a solvent immediately after welding. Further, the temperature range of the solvent is preferably from 60 to 100 ° C.

[0035] As the treatment solvent used in the present invention, it is preferable to use an aqueous solution containing an inorganic acid salt selected from the group consisting of silicates, borates, phosphates, and sulfates. It is preferably an aqueous solution containing a salt. For example, an aqueous solution containing a double salt compound of the above-mentioned inorganic acid salt and ammonium salt can be suitably used. More specifically, the strength of an aqueous solution of ammonium fluoride is not limited to this.

[0036] By using the above treatment solvent, the tin can be oxidized to such an extent that the solder wettability is not adversely affected. In the tab terminal of the present invention, from the viewpoint of suppressing whisker generation as described above, it is preferable that tin oxide is formed in the welded portion, but if all of the metal tin is oxidized to tin oxide. Solder wettability deteriorates. Therefore, the ratio between metal tin and tin oxide needs to be appropriate. By oxidizing metal tin using an aqueous solution containing the above-mentioned inorganic acid salt or ammonium salt, the ratio of metal tin to tin oxide can be made appropriate. The concentration of the aqueous solution is preferably 110% by weight.

Example

[0037] A lead wire (CP wire) made of iron / copper and an aluminum core wire, each of which was provided with a 100% tin plating as a lead wire, were cut into predetermined lengths. After the cut lead wire and the aluminum core wire were welded by arc discharge, the tab portion 1 was obtained by pressing the aluminum core wire portion by pressing. The obtained tab terminal 1 is degreased and washed with a paraffinic solvent. Then, hot air drying was performed at 80 ° C for 12 minutes.

[0038] The degreased tab terminal 1 is placed in a thermo-hygrostat (PVH-

110: manufactured by Tabai Espec Corp.) (Examples 14 to 14 and Comparative Example 1). In addition, the sample which was not subjected to the heat treatment was Comparative Example 2.

Next, to observe the whiskers of the sample subjected to the heat treatment (Example) and the sample not subjected to the heat treatment (Comparative Example), the temperature was set to 60 ° C. × 90. A 250-hour accelerated test was performed under the condition of / oRH. After the accelerated test, whiskers generated in the welds of each sample were observed using a 30-fold optical microscope, and the length of the die force generated in the tab terminal welds was measured.

[0040] Further, in order to examine the solder wettability of each sample before performing the above-mentioned accelerated test, JIS C-0

The zero crossing time (ZCT value) was measured by the 053 soldering test method (equilibrium method). Table 1 shows the measurement results.

[table 1]

table 1

Next, the tab terminal 1 described above was immersed in a 1.0% by weight aqueous solution of sodium metasilicate at 120 ° C. for 2 minutes to perform a solvent treatment to obtain a sample 6. The obtained sample was subjected to an acceleration test for 250 hours under the conditions of 60 ° C. and 90% RH. After the acceleration test, the length of the force generated at the welding portion of the tab terminal was measured by the same measuring method as described above. Further, the solder wettability of the sample subjected to the solution treatment in the same manner as above was measured. Table 2 shows the measurement results.

[0042] Further, within 300 ms after welding the above-mentioned lead wire and aluminum core wire by arc discharge, a 5% by weight aqueous solution of ammonium fluoride was applied and adhered to the welded portion. Then, press the aluminum core wire by pressing in the same manner as above to make tab terminal 2 (test Fee 7). The obtained tab terminal 2 was degreased and washed with a paraffin-based solvent, and dried with hot air at 80 ° C for 12 minutes.

The obtained samples 6 and 7 were subjected to an acceleration test in the same manner as above, and the length of the die force and the solder wettability were measured. The results were as shown in Table 2

[Table 2]

Table 2

Whisker length Z CT value

麵 Solvent solder wettability

(mm) (s) Separation 6 (Example 4) Sodium metasilicate 0.15 2.40

X7 (Fibre Example 5) 0.086 2.35 〇

Ammonium 5 (Comparative Example 2) None 0.23 2.50 〇

Claims

The scope of the claims

[I] A tab terminal for an electrolytic capacitor in which an aluminum core wire having a pressed portion is welded to an end portion of a lead wire having a metal layer made of tin formed on a core material surface, wherein the lead wire and the lead wire are connected to each other. A tab terminal for electrolytic capacitors in which the welded part with the aluminum core wire is treated to suppress the growth of wire force.

[2] The tab terminal according to claim 1, wherein the whisker suppression treatment is a tin oxide formation treatment.

3. The tab terminal according to claim 2, wherein the tin oxide forming treatment causes at least SnO or Sn〇 to be contained in a welded portion between the lead wire and the aluminum core wire.

2

4. The tab terminal according to claim 1, wherein the tin oxide forming treatment is performed by heat-treating the tab terminal.

[5] The tab terminal according to claim 4, wherein the heat treatment is performed in an oxygen atmosphere in a range of 60 to 180 ° C.

[6] The tab terminal according to claim 4, wherein the heat treatment is performed in an oxygen atmosphere at a temperature in the range of 80 to 150 ° C.

7. The tab terminal according to claim 13, wherein the tin oxide forming treatment is performed by a solvent treatment.

[8] The solvent treatment is performed immediately after welding the aluminum core wire to the end of the lead wire.

The tab terminal according to claim 7.

[9] The tab according to claim 7, wherein the solvent is an aqueous solution containing an inorganic acid salt selected from the group consisting of silicates, borates, phosphates, sulfates, and mixtures thereof. Terminal.

[10] The tab terminal according to claim 9, wherein the solvent is an aqueous solution further containing an ammonium salt.

[II] The tab terminal according to claim 9 or 10, wherein the concentration of the aqueous solution is 1 to 10% by weight.

[12] The method for manufacturing a tab terminal according to claim 11, wherein

A step of preparing a tab terminal by welding an aluminum core wire having a pressing portion to an end of a lead wire in which a metal layer made of tin is formed on a core material surface, and Heat-treating the welded tab terminal,

A method for manufacturing a tab terminal.

13. The production method according to claim 12, wherein the heat treatment is performed in an oxygen atmosphere at a temperature in the range of 60 to 180 ° C.

[14] The production method according to claim 12, wherein the heat treatment is performed in an oxygen atmosphere at a temperature in the range of 80 to 150 ° C.

[15] The method for producing a tab terminal according to claim 11, wherein

A step of welding an aluminum core wire having a pressing portion to an end of a lead wire in which a metal layer made of tin is formed on the surface of the core material, and

A step of applying and attaching a solvent to the welded portion,

A method for manufacturing a tab terminal.

16. The production method according to claim 15, wherein the step of attaching the solvent is performed immediately after welding.

17. The production method according to claim 16, wherein the step of attaching the solvent is further performed at the time of cleaning the tab terminal.

18. The method according to claim 15, wherein the solvent is an aqueous solution containing an inorganic acid salt selected from the group consisting of silicates, borates, phosphates, sulfates, and mixtures thereof. The manufacturing method according to item 1.

[19] The method according to claim 18, wherein the solvent is an aqueous solution further containing an ammonium salt.

[20] The production method according to claim 18 or 19, wherein the concentration of the aqueous solution is 0.5 to 10% by weight.

21. The method according to claim 15, wherein the temperature of the welded portion when applying a solvent to the welded portion is 80 to 250 ° C.

22. The method according to claim 15, wherein the temperature of the solvent is 60 to 100 ° C.