JP2006322027A - Fuse element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuse element made of Zn-Al-containing alloy and built into a tantalum capacitor etc. by which fusion temperature of fuse can be sufficiently lowered and safety against soldering mounting using a lead-free soft solder can be maintained. <P>SOLUTION: An alloy having a composition which comprises Zn, Al and Ge and in which respective contents of Al and Ge are made to 0.5 to 15%, respectively, total amount of Al and Ge are 5 to 20% and the balance is composed of Zn is worked into a fine wire. The respective contents of Al and Ge are made to 0.5 to 1.5%, respectively, in order to regulate the ratio between melting heat quantity at 260 to 370°C (H<SB>(260 to 370°C)</SB>) and total melting heat quantity (ΣH), H<SB>(260 to 370°C)</SB>/ΣH, to ≥0.2 to make the fusion temperature of the fuse element markedly lower than the fusion temperature of a Zn-Al fuse element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuse element, and is useful as a fuse element used in an electronic component such as a capacitor or a transistor.

In an electronic component, the current fuse element is connected to the component main body, and these may be sealed with a resin mold or the like.
For example, in a tantalum capacitor, a fuse element is connected to a capacitor element and is molded with a resin in order to prevent overcurrent due to a wrong polarity mounting. It is also known to connect fuse elements to power transistors and seal them with resin.

These electronic components with a built-in fuse are heated at the heat generation temperature of the fuse element when the fuse is blown.
Thus, in order to prevent carbonization and combustion of the electronic component body and the mold resin, it is necessary to keep the heat generation temperature below a predetermined smoke generation temperature.
Therefore, in order to cut off the energization by fusing the fuse element before the electronic component smokes, the fusing temperature of the fuse element is sufficiently lower than the fume temperature of the electronic component to which the fuse element is attached, such as a tantalum capacitor or a power transistor. It is requested to do.

  Since the electronic component with a fuse element is usually mounted on a circuit board by a reflow method or a flow method, the fuse element must be able to withstand this soldering temperature. It must be higher than the soldering temperature.

  Conventionally, in order to prevent environmental pollution due to elution of lead ions from discarded electronic / electrical electronic parts, the use of lead-free solder has been requested, and Sn-Ag, Sn-Cu, Sn-In, Sn-Bi based lead-free solder has been developed. The mounting temperature using these lead-free solders is higher than that in the case of using Pb—Sn solders, and is approximately 260 ° C.

Corresponding to this lead freezing of solder, lead freezing is also demanded in the fuse element.
Conventionally, as a lead-free fuse element having an operating temperature of 300 to 400 ° C., an “alloy of 0.5 to 17% Al and the balance of Zn processed into a thin wire” has been proposed (Patent Document 1).
JP-A-10-134698

FIG. 2-1 shows a phase diagram of a Zn—Al alloy, where the liquidus temperature is between about 440 ° C. and about 380 ° C. when Al is 0.5 to 17%, and the solidus temperature is about 380 ° C. It is.
FIG. 2-2 shows the DSC (Differential Scanning Calorimetry) result of Zn-5Al, starting to dissolve at approximately 380 ° C. and completing dissolution at approximately 389 ° C. and being completely liquid phase (284.8 ° C. The peak of is due to crystal transformation and is not involved in dissolution).
When the alloy is heated and exceeds the solidus temperature, the liquid phase starts and the solid content decreases and becomes a solid-liquid coexistence state. Become.
Usually, the fusing of the fuse element occurs between the solidus temperature and the liquidus temperature. Thus, the fusing temperature of the fuse element described in Patent Document 1 is 380 ° C. to 440 ° C. according to the state diagram of FIG. 2-1.
At the fusing temperature of 380 ° C. to 440 ° C., there is little margin with respect to the smoke generation temperature of electronic components to which the fuse element is attached, such as tantalum capacitors and power transistors, and in order to lower the fusing temperature, Au, Ag, Cu, Ni, Pd, Patent Document 1 discloses that 0.1% to 5% of at least one selected from P is added.

However, when these elements are added, even when the solidus temperature can be lowered, the heat of solution at 260 ° C. to 370 ° C. is only about several percent of the total heat of solution, and the liquid phase is formed at 260 ° C. to 370 ° C. Is slight.
In this case, even if the fuse element starts to melt at a relatively low temperature, the temperature at which the fuse element is blown is not lower than that of an additive-free Zn—Al fuse element such as Au.

  The object of the present invention is based on such knowledge, and in a fuse element made of an alloy containing Zn-Al incorporated in a tantalum capacitor or the like, the fuse fusing temperature can be sufficiently reduced, and it is safe for solder mounting by lead-free solder. An object of the present invention is to provide a fuse element that can be held.

The fuse element according to claim 1 contains Zn, Al, and Ge, the content of each of Al and Ge is 0.5 to 15%, the total amount of Al and Ge is 5 to 20%, The balance is characterized in that the alloy of Zn is processed into a thin wire. The reason why the respective contents of Al and Ge are 0.5 to 15% is the ratio of the heat of dissolution H _{260 ° C. to 370 ° C. at 260 ° C. to 370 ° C.} and the total heat of heat ΣH H _{260 ° C. to 370 ° C.} / This is because ΣH is set to 0.2 or more, preferably 0.5 or more to make the fuse element fusing temperature much lower than the fusing temperature of the Zn-Al fuse element. If it exceeds 15%, dissolution occurs even at around 260 ° C. and lead-free soldering is difficult to perform safely. The reason why the total amount of Al and Ge is 5 to 20% is to enable easy thin wire processing, and if it is less than 5%, it is fragile and difficult to draw, and if it exceeds 20%, the ductility is large. This is because it becomes too difficult to draw the line.

The fuse element according to claim 2 contains at least one of Zn, Al, Mg, Sn, In, Ga, and Ge, and each of at least one of Al, Mg, Sn, In, Ga, and Ge. A content of 0.5 to 15%, a total amount of Al and at least one of Mg, Sn, In, Ga, and Ge is 5 to 20%, and the balance of Zn is processed into a thin wire. And The reason why the content of each of at least one of Al and Mg, Sn, In, Ga, and Ge is 0.5 to 15% is that the heat of dissolution at _{260 ° C. to 370 ° C.} H _{260 ° C. to 370 ° C.} is completely dissolved The ratio H with heat quantity ΣH H _{260 ° C. to 370 °} C./ΣH is set to 0.2 or more, preferably 0.5 or more to make the fuse element fusing temperature much lower than the fusing temperature of the Zn—Al fuse element. If the ratio is less than 0.5%, the ratio cannot be increased to 0.2 or more. If the ratio exceeds 15%, dissolution occurs even in the vicinity of 260 ° C., and it is difficult to perform lead-free soldering safely. The reason why the content of each of Al and at least one of Mg, Sn, In, Ga, and Ge is 5 to 20% is to facilitate the thin wire processing, and is less than 5%. This is because it is difficult to draw, and if it exceeds 20%, the ductility becomes too large and drawing becomes difficult.

The fuse element according to claim 3 is characterized in that an alloy in which at least one of Mg, Sn, In, and Ga is 3 to 20% and the balance is Zn is processed into a thin wire. The reason why the total content of at least one of Mg, Sn, In, and Ga is 3 to 20% is that the ratio of the heat of dissolution H _{260 ° C. to 370 ° C. at 260 ° C. to 370 ° C.} and the total heat of heat ΣH H _{260 C. to 370.degree.} C./.SIGMA.H is set to 0.2 or more, preferably 0.5 or more to make the fuse element fusing temperature much lower than the fusing temperature of the Zn-Al fuse element. If it exceeds 20%, dissolution occurs even at around 260 ° C., and lead-free soldering is difficult to perform safely.

  A fuse element according to claim 4 is a thin wire alloy in which at least one of Bi, Au, Ag, Cu, Ni, Pd, P, and Sb is added to the alloy according to any one of claims 1 to 3 in an amount of 1% or less. It is characterized by being processed. The reason for adding Bi, Au, Ag, Cu, Ni, Pd, P, and Sb is to increase the compatibility of the fuse element with the electrode connected by spot welding or the like, and mechanically toughen the interface with the electrode. This is because a strong alloy layer is formed to improve the bonding strength.

  The fuse element according to claim 5 is the fuse element according to any one of claims 1 to 4, wherein the thin wire section has a circular shape with a wire diameter of 0.03 to 0.6 mmφ or a thickness of 0.01 to 0.2 mm. It is characterized by a ribbon shape with a width of 3 to 0.1 mm.

(1) Contain no metallic elements harmful to the living body and contribute to environmental conservation. Furthermore, it has excellent corrosion resistance and can be used safely in corrosive environments.
(2) Heat of dissolution H at _{260 ° C. to 370 ° C. Ratio} H _{260 ° C. to 370 ° C.} and total heat of fusion ΣH _{260 ° C. to 370} ° C./ΣH is 0.2 or more, and the solidus temperature is set to 260 ° C. In addition, the liquid phase can be sufficiently advanced in the temperature range of 260 ° C. to 370 ° C., and the fuse can be blown at 370 ° C. or lower. Since this temperature is sufficiently lower than the fuming temperature of a tantalum capacitor or the like, it is possible to reliably prevent fuming of the tantalum capacitor or the like.
(4) Since the solidus temperature is 260 ° C. or higher, an electronic component with a fuse element can be safely mounted on a circuit board even by soldering with lead-free solder.
Therefore, according to the fuse element of the present invention, a lead-free fuse that can prevent smoke generation of a tantalum capacitor or the like by a quick operation, can perform lead-free soldering safely, and can be easily attached to an electronic component. An element can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a capacitor incorporating a fuse element according to the present invention.
In FIG. 1, 1 is a tantalum capacitor element, and 2 is an anode lead conductor. Reference numeral 3 denotes a wiring board having a pair of electrodes 31 and 32, connecting the fuse element a according to the present invention between the electrodes, joining one electrode 31 to the cathode of the capacitor element 1, and The lead conductor 4 is joined to the electrode 32. 5 is a sealing resin layer, for example, an epoxy resin layer.
For joining the fuse element and the electrode, resistance welding, ultrasonic welding, wire ball bonding, wedge bonding, heat pressure welding, or the like can be used.

  The capacitor is mounted on a circuit board at a temperature of 230 ° C. to 280 ° C. by a reflow method or a flow method using lead-free solder together with other electronic components such as an IC, a transistor, and a chip resistor.

The reason why the fuse element is built in the tantalum capacitor is to prevent overcurrent from flowing and generating smoke due to an incorrect polarity connection.
In addition to the temperature, the fuse shut-off time is also involved in the smoke generation. If the fuse shut-off time is long, smoke is emitted at a low temperature, and the fuse shut-off time becomes longer as the fuse element resistance decreases. Also involved.
Therefore, the specific resistance of the fuse element attached to the capacitor or the like is 5.0 to 6.0 μΩcm, and the fuse cutoff time is 60 to 90 msec. It is effective to make the temperature lower than 400 ° C. as much as possible and higher than 260 ° C. in the lead-free solder mounting.

The cross-sectional dimension and shape of the fuse element are a round wire having a wire diameter of 0.03 to 0.6 mmφ or a ribbon having a thickness of 0.01 to 0.2 mm and a width of 3 to 0.1 mm.
The upper limit is to reduce the cross-sectional area of the fuse element and prevent the cut-off time from becoming too long. The lower limit is handling when the fuse element is built in an electronic component, assembly workability, drawing process Is to guarantee performance and cost reduction.
The ribbon shape having a thickness of 0.01 to 0.2 mm and a width of 3 to 0.1 mm has an advantage that the contact area with the electrode can be sufficiently widened to improve the bondability.

The fuse element according to the present invention can be safely soldered with scissors even after repairing or retrofitting after mounting by the reflow method or the flow method.
In these cases, the fuse element is bent but has sufficient flexibility and can be mounted, mounted or retrofitted smoothly without breakage.

The fuse element according to the present invention can be obtained by melting a base metal at a predetermined blending ratio, casting a billet, and drawing the billet.
As the Zn ingot, one containing impurities Pb, Fe, Cd and the like within the range defined by JISH2107 can be used.

In addition to this drawing process, it can also be produced by spinning in a rotating liquid. That is, the molten jet sprayed from the nozzle is incident on the cooling liquid layer formed and held on the inner peripheral surface of the rotating drum by centrifugal force at the same speed and in the same direction as the peripheral speed of the cooling liquid layer, and this liquid layer incident jet is It can also be spun by rapid cooling and solidification in the cooling liquid layer. In this case, the jet in the space from the nozzle to the coolant layer has a circular cross section with the circular shape of the nozzle being held by the surface tension of the molten metal. Furthermore, the peripheral velocity of the cooling fluid layer, the incident angle of the cooling fluid layer of the jet, etc. are set so that the circular holding force due to the surface tension of the jet is larger than the dynamic pressure of the cooling fluid layer (pressure for flattening the jet). The jet that has been adjusted and entered the cooling liquid layer is cooled and solidified while maintaining a circular cross section. Accordingly, even a thin fuse element having a wire diameter of 30 μm can be easily manufactured.
During these wire making operations, winding onto a bobbin is required, or for sufficient flexibility, it can be wound smoothly without breakage.

A thin wire having a wire diameter of 60 μmφ was produced by die drawing with an alloy composition of Al: 5.0%, Ge: 2.0%, and the balance Zn. The result of DSC (temperature increase rate: 10 ° C./min) of this alloy is as shown in FIG. 3. When H _{260 ° C. to 370 °} C./ΣH was determined, it was 0.8 or more.
This thin 3 mm piece was resistance-welded between the Ag-plated 42 alloy electrodes, a thermoelectric thermometer was placed at a position 0.5 mm above the center of the fine line, and 3A was energized to measure the fuse cutoff temperature. It was as follows (n = 10 average values).
In addition, a thin wire was resistance-welded to 42 alloy electrodes (n = 10 average values), 100% of the thin wire cut by applying a tensile force was joined, and 50 to 90% of the thin wire cut was joined. When the bondability was evaluated as a bondability x with 10% to 40% of the thin line cut or 100% of the bonded part peeled off, the evaluation was good.
Further, heating was performed at 260 ° C. for 10 seconds to check whether there was a change in the resistance value, but no abnormality was observed.

[Comparative Example 1]
A fine wire was produced in the same manner as in Example 1 except that Ge was not added to Example 1. The result of DSC is as shown in FIG. 2-2, and H _{260 ° C. to 370 °} C./ΣH was 0.
Moreover, when the cutoff temperature was measured like Example 1, it was 390 degreeC or more. The bondability was good.
From the comparison between Comparative Example 1 and Example 1, it was confirmed that the fuse blowing temperature could be reduced by 20 ° C. or more as compared with the case of no addition by addition of Ge.

[Example 2 to Example 5]
As shown in Table 1, with respect to Example 1, except that the Al amount and Ge amount were changed, a thin wire was produced in the same manner as in Example 1, and H _{260 ° C. to 370 °} C./ΣH, fuse fusing temperature, and bondability were The results were as shown in Table 1.
Although it was heated at 260 ° C. for 10 seconds and checked for the presence or absence of fluctuations in resistance, no abnormality was observed.

[Examples 6 to 13]
As shown in Table 2, a thin wire was manufactured in the same manner as in Example 1 except that Bi, Ag, Cu, Ni, Pd, P, and Sb were added to Example 1, and H260 to 370 ° C./ΣH and fuse It was as Table 2 when fusing temperature and bondability were calculated | required.
Any example product was heated at 260 ° C. for 10 seconds to check whether there was a change in resistance value, but no abnormality was observed.

[Examples 14 to 18]
As shown in Table 3, a thin wire was produced in the same manner as in Example 1 except that the composition contained at least one of Zn, Al, Mg, Sn, In, and Ga. H260 to 370 ° C./ΣH and fuse The fusing temperature and bondability were determined as shown in Table 3.
Any example product was heated at 260 ° C. for 10 seconds to check whether there was a change in resistance value, but no abnormality was observed.
In any of the examples, it was confirmed that the joining property could be improved by adding 0.5% of any of Bi, Ag, Cu, Ni, Pd, P, and Sb.

[Comparative Examples 2 to 3]
As shown in Table 3, containing Zn, Al and Sn or In, except that the total amount of Al and Sn, or In is less than 5%, to produce a fine line in the same manner as in Example _{1, H 260 ° C.} It was as Table 3 when -370 _degreeC / (Sigma) H, fuse fusing temperature, and joining property were calculated | required.

[Example 19 to Example 23]
A thin wire was produced in the same manner as in Example 1 except that the alloy composition shown in Table 4 was used, and the solidus temperature and specific resistance were measured in the same manner as in Example 1. As a result, H _{260 ° C. to 370 °} C./ΣH and The fuse fusing temperature and bondability were determined as shown in Table 3.
Although it was heated at 260 ° C. for 10 seconds and checked for the presence or absence of fluctuations in resistance, no abnormality was observed.
In any of the examples, it was confirmed that the joining property could be improved by adding 0.5% of any of Bi, Ag, Cu, Ni, Pd, P, and Sb.

It is drawing which shows an example of the electronic component with a fuse concerning this invention. It is a temperature state figure of a Zn-Al alloy. It is a DSC result of a Zn-5Al alloy. It is a DSC result of a Zn-5Al-2Ge alloy.

Explanation of symbols

a fuse element 1 capacitor element 5 sealing resin layer

Claims (5)

An alloy containing Zn, Al and Ge, each containing Al and Ge of 0.5 to 15%, the total amount of Al and Ge being 5 to 20%, and the balance being Zn is processed into a thin wire. A fuse element characterized by comprising: Zn, Al, and at least one of Mg, Sn, In, Ga, and Ge, and each content of Al and at least one of Mg, Sn, In, Ga, and Ge is 0.5 to 15%, A fuse element obtained by processing an alloy of Al and at least one of Mg, Sn, In, Ga, and Ge into a thin wire of 5 to 20% and the balance of Zn. A fuse element, wherein an alloy in which at least one of Mg, Sn, In, and Ga is 3 to 20% and the balance is Zn is processed into a thin wire. An alloy in which at least one of Bi, Au, Ag, Cu, Ni, Pd, P, and Sb is added in an amount of 1 weight or less to 100 parts by weight of the alloy according to any one of claims 1 to 3 is processed into a thin wire. A fuse element. The thin wire cross-section is a circular shape having a wire diameter of 0.03 to 0.6 mmφ or a ribbon shape having a thickness of 0.01 to 0.2 mm and a width of 3 to 0.1 mm. -Element.

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