JP2001325876A - Fuse element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly achieve lead-free state in Sn system of a fuse element embedded in electrical parts, such as a tantalum capacitor, while satisfactorily ensuring stable implementation of fuse-embedded electrical parts by lead-free solder and prevention of carbonization and/or burning of the electrical parts at fuse-fusing action. SOLUTION: Hypercomplex alloy of liquidus temperature of 300 deg.C to 550 deg.C, in which two kinds or more of other metallic elements such as Ag, Cu, Ni, Ge, Al are combined with Sn, is worked into a small diameter wire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuse element, and more particularly to a fuse element useful as a fuse element incorporated in an electric component such as a capacitor or a transistor.

[0002]

2. Description of the Related Art In an electric component, a current fuse element is sometimes connected to an electric component main body, and these are sealed with a resin mold or the like. For example, in a tantalum capacitor, a fuse element is connected to a capacitor element in order to prevent an overcurrent caused by incorrect polarity mounting.
These are molded with resin. It is also known to connect a fuse element to a power transistor and seal them with a resin.

[0003] These electronic components with a built-in fuse are heated at the temperature at which the fuse element is heated when the fuse is blown. Therefore, in order to prevent carbonization and combustion of the electric component body and the mold resin, it is necessary to suppress the heat generation temperature to a predetermined temperature or less. That is, assuming that the fusing current is i, the fusing time is tm, the fusing temperature of the fuse element is Tm, the resistance is R, the heat capacity per unit length of the fuse element is K, and the ambient temperature is θ. Almost

[Number 1] tm = K (Tm-θ) / Ri 2 (1) is satisfied, it is necessary to suppress the Tm below a predetermined temperature.

[0004] The above-mentioned electric component with a built-in fuse is usually mounted on a circuit board by a reflow method or a flow method.

[0005]

Conventionally, Pb-Sn based solder has been used in the reflow method and the flow method, and the mounting temperature has been set at 220 to 230 ° C. Conventionally,
Based on the premise that an alloy having a solidus temperature higher than the mounting temperature is used for the fuse element, Pb-1 to 10S
n, Pb-0.5-10Sn-1-5Ag, Pb-1
20In, Pb-1-20In-1-5Ag, Pb-
Pb-based alloys (melting point: 260 ° C. to 330 ° C.) such as 0.5 to 5 In-0.1 to 5 Cu are used. In these alloy-based fuse elements, since the solidus temperature is higher than the mounting temperature, it is possible to guarantee the safe mounting of the fuse built-in electrical components. Also, the liquidus temperature is about 330 ° C.
The temperature Tm at the time of fusing of the fuse element can be sufficiently lowered,
The fuse element can be safely blown without causing carbonization and combustion of the electric component body and the mold resin.

[0006] Recently, in order to prevent environmental pollution due to elution of lead ions from discarded electronic and electrical equipment, use of lead-free solder has been demanded.
Lead-free solders such as Sn-Cu, Sn-In and Sn-Bi have been developed. The mounting temperature using these lead-free solders is higher than that using Pb-Sn solder, and is expected to be 280 ° C. at the maximum. In response to the lead-free solder, the fuse element is required to be lead-free. However, it is necessary to use an alloy having a solidus temperature higher than the mounting temperature as in the related art. Assuming that the fuse element is lead-free, the mounting temperature is 280.
Alloys having a solidus temperature higher than ° C. will be used for fuse elements. Thus, the liquidus temperature of the fuse element becomes considerably higher than the liquidus temperature of the conventional Pb-based fuse element, and the fusing temperature Tm of the fuse element becomes higher. -It is dangerous because carbonization and combustion are likely to occur in the electric component body or mold resin at the time of fusing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuse element incorporated in an electric component such as a tantalum capacitor, and to stably mount the electric component with a built-in fuse with lead-free solder and to operate the electric component when the fuse is blown. An object of the present invention is to achieve a satisfactory lead-free Sn-based fuse element in the fuse element while sufficiently preventing carbonization and combustion.

[0008]

The fuse element according to the present invention has a liquidus temperature of 300 ° C. or more in which Sn is mixed with two or more other metal elements such as Ag, Cu, Ni, Ge, and Al. 55
This is a configuration characterized by processing a multi-element alloy at 0 ° C. into a fine wire, and the compounding amounts of other metal elements are Ag: 5 to 30% by weight, Cu: 1 to 15% by weight, Ni: 0.5 to 5%. weight%,
Ge: 1 to 10% by weight, Al: 1 to 10% by weight. A preferred configuration of the fuse element according to the present invention is Ag5.
-30% by weight, 1-15% by weight of Cu, and the rest Sn as a multi-element alloy processed into a thin wire.

[Action] The solidus temperature is about 210 ° C. to 23 ° C.
0 ° C, mounting temperature of 260 ° C with lead-free solder
Although it is lower than 280 ° C, the liquidus temperature of the fuse element is 3
Since the temperature is higher than 00 ° C. and higher than the mounting temperature, the fuse element does not become a complete liquid at the time of mounting, but becomes a semi-molten state, has poor wettability to the fuse electrode, and has a poor fuse property. Since the wire element has a small wire diameter of 50 μm to 150 μm and has a large linear holding force (f / r where r is the wire diameter and f is the surface tension) due to the surface tension, it will be apparent from the examples described later. In addition, without substantial damage of the fuse element,
Electrical components with built-in fuse elements can be mounted.

Further, the liquidus temperature of the fuse element is set to 550.
C. or less, the Tm can be suppressed to 600.degree. C. or less and the fuse element can be formed without carbonizing or burning the electric component body or the mold resin, as is apparent from the examples described later. Can be safely blown. In addition, in order to set the liquidus temperature to 300 ° C. to 550 ° C. in a binary alloy of Sn and one of the other metal elements, it is necessary to increase the blending amount of the other metal element. In the case of (1), the amount of Ag needs to be 10 to 55% by weight or more, and when the amount of Ag is 25% by weight or more, the alloy is remarkably weakened. However, in the fuse element according to the present invention, Sn, Ag, C
u, Ni, Ge, Al, etc., two or more other metal elements are blended. As is clear from the comparison between Examples and Comparative Examples described later, the liquidus temperature can be reduced with a small amount of other metal elements. It is possible to prevent the fuse element from becoming brittle and to prevent the fuse element from being broken at the time of bending at the time of mounting or winding the bobbin at the time of wire drawing.

[0011]

Embodiments of the present invention will be described below 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, a fuse element a according to the present invention is connected between the electrodes, one electrode 31 is joined to the cathode of the capacitor element 1, and the other is connected. The lead conductor 4 is joined to the electrode 32. Reference numeral 5 denotes a sealing resin layer, for example, an epoxy resin layer. The fuse element and the electrode are joined by resistance welding,
Wire ball bonding, wedge bonding, or the like can be used.

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

The alloy of the fuse element according to the present invention includes S
A multi-component alloy in which two or more kinds of other metal elements such as Ag, Cu, Ni, Ge, and Al are mixed into n and the liquidus temperature is adjusted to 300 ° C. to 550 ° C. is used. A
g: 5 to 30% by weight, Cu: 1 to 15% by weight, Ni:
0.5 to 5% by weight, Ge: 1 to 10% by weight, Al: 1 to 1%
It is 10% by weight. Below the lower limit, the liquidus temperature is 3
When the temperature exceeds 00 ° C and exceeds the upper limit, the liquidus temperature becomes 5 ° C.
This is because the temperature will be 50 ° C. or higher. The wire diameter is usually 50μ.
m to 150 μm.

In this fuse element, the solid phase temperature is 214
° C to 230 ° C, and the mounting temperature is 230 ° C to 280 ° C.
Under the condition, the solid phase particles are mixed in the liquid phase, the wettability is poor, and the thinning of the fuse element due to the spread of the wettability to the electrodes during mounting heating is slightly suppressed. It is possible to maintain the original thickness by cooling and solidifying at the end of mounting. Therefore, the above-mentioned fuse built-in capacitor is
Mounting temperature 240 ° C higher than the solidus temperature of the
Even with the reflow method or the flow method using lead-free solder at 280 ° C., the fuse element can be mounted while being held stably.

The reason why the fuse element is incorporated in the tantalum capacitor is to prevent an overcurrent from flowing due to an erroneous connection of the polarity. The interruption current is i, the interruption time is tm, and the fuse is not used. Assuming that the temperature at the time of fusing of the element is Tm, the resistance is R, the heat capacity per unit length of the fuse element is K, and the ambient temperature is θ, the above equation (1) is obtained.
Holds. The fuse element according to the present invention has a wire diameter of 50 μm
Under φ ~ 150μmφ, overcurrent can be cut off at 2-6A with a cut-off time of several milliseconds and at the time of fusing of the fuse element below 600 ° C, and the smoke temperature of the tantalum sintered body is 600 ° C.
The fusing operation can be safely performed in the following.

The fuse element according to the present invention can be mounted on a tantalum capacitor as described above.
The fuse element alone may be mounted on the fuse electrode of the circuit board by the above-mentioned reflow method or flow method. Further, the fuse element according to the present invention includes:
Even after repairing or mounting after mounting by the reflow method or the flow method, it is also possible to safely solder with a trowel. In these cases, the fuse element is subject to bending, but has sufficient flexibility and can be smoothly mounted, mounted or retrofitted without breakage.

The fuse element according to the present invention uses a multi-component alloy having sufficient flexibility.
50 μmφ wire drawing can be performed smoothly. In addition to this drawing process, it can also be manufactured by spinning in a rotating liquid. That is, the molten liquid jet formed from the nozzle is incident on the cooling liquid layer formed and held by centrifugal force on the inner peripheral surface of the rotating drum at the same speed and in the same direction as the peripheral speed of the cooling liquid layer,
The liquid layer incident jet can be quenched and solidified in a cooling liquid layer and spun. In this case, the jet in the space from the nozzle to the cooling liquid layer has a circular cross-section because the circular shape of the nozzle is held by the surface tension of the molten metal. Further, the peripheral speed of the cooling liquid layer, the incident angle of the cooling liquid layer of the jet, and the like 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 liquid layer (the pressure for flattening the jet). The jet that has been adjusted and incident on the cooling liquid layer also cools and solidifies while maintaining a circular cross section. Therefore, a fuse element having a fine wire having a wire diameter of 50 μmφ to 150 μmφ can be easily manufactured. During the wire drawing, winding onto a bobbin is required, or because of sufficient flexibility, it can be wound smoothly without breakage.

[0018]

[Examples] [Examples 1 to 6] Inside diameter 500 mm, width 45 m
m is rotated at 200 rpm to about 1600 ml
Water is formed in a layered form, and a composition melted by a heater is jetted into the cooling liquid layer as a jet from a quartz glass nozzle at the same speed as the peripheral speed of the cooling liquid layer by pressurizing nitrogen gas. According to the spinning method, Sn-Ag-Cu shown in Table 1 was used.
A thin wire having a wire diameter of about 100 μmφ was manufactured from the alloy, and this was used as a fuse element.

Comparative Example 1 As shown in Table 1, the alloy was S
The same as in the above example, except that n-40 wt% Ag was binary.

The solidus temperature and liquidus temperature, the rate of change in resistance, the current interruption characteristics (interruption time and temperature), and the flexibility of these examples and comparative examples were measured. (Average value of 20 samples).

The measuring method is as follows. [Solidus temperature and liquidus temperature] The measurement conditions by DSC were a heating rate of 10 ° C / min. [Rate of change in resistance value] This is for evaluating the possibility of mounting at a temperature of 280 ° C. As shown in FIG. 2, counter electrodes 62 and 62 are provided on a ceramic substrate 61 by applying and firing an Ag paste, a fuse element a is placed between the electrodes, and tin-plated copper is further provided on each electrode 62. A wire 63 was welded, and a sample in which each electrode and the fuse element a were welded by the welding heat was kept at 280 ° C. for 10 minutes, and the resistance change rate with respect to the initial value at 10 minutes was measured. [Interruption current characteristics] A current of 5 A flows through the fuse element.
The cut-off time and the fuse element temperature at the time of cut-off were measured. [Flexibility] 180 ° fuse element about 100mm long
When the test piece was bent and not broken, the test was passed.

[0022]

[Table 1]

In the fuse element according to the present invention, even if the melting start temperature (solidus temperature) is lower than the maximum mounting temperature of 280 ° C., the liquidus temperature is 300 ° C. or more and the temperature is 280 ° C.
In the semi-molten state, the electric component incorporating the fuse element according to the present invention has a high temperature of 280 ° C. Even if the fuse element is originally mounted, the fuse element can be stably held without substantial thinning. This can be confirmed from a sufficiently small resistance change rate of 10% or less.

Further, in the fuse element according to the present invention, the liquidus temperature is 550 ° C. or less, which is sufficiently low, and the temperature of the fuse element at the time of fusing can be suppressed to 600 ° C. or less. Table 1 shows that the carbonization and combustion of the sealing resin can be prevented.
It can also be confirmed from the temperature at the time of fusing of the current interrupting characteristics. Also,
From the comparison with Comparative Example 1, in order to obtain the characteristics equivalent to the example with the binary alloy, it is inevitable that the flexibility is deteriorated, and it is difficult to mount the capacitor on a capacitor or to use it industrially from the viewpoint of wire drawing. According to the invention, it is clear that industrial use can be made smoothly without such obstacles.

[Embodiment 7] Sn-20Ag- of Embodiment 3
The same as Example 3 above except that Sn-20Ag-1Ni was used for 5Cu.

Embodiment 8 Sn-20Ag- of Embodiment 3
The same as Example 3 above, except that Sn-20Ag-4Ge was used for 5Cu.

The solidus temperature and liquidus temperature, resistance value change rate, current interruption characteristics (interruption time and temperature), and flexibility of these examples were measured.

[Table 2] From the comparison between Example 3 and Examples 7 and 8, N
The substitution usefulness of i and Ge can be confirmed. For Al,
Also confirmed.

Example 9 The alloy composition was changed to Sn-5Cu-1.
It was the same as Example 1 except that Ni was used.

[Comparative Example 2]

Example 1 was the same as Example 1 except that the alloy composition was Sn-20Cu. When the solidus temperature and liquidus temperature, the rate of change in resistance value, the current interruption characteristics (interruption time and temperature), and the flexibility of this example and comparative example 2 were measured,
Table 3 shows the results.

[Table 3] It is clear from the comparison between Example 9 and Comparative Example 2 that the poor flexibility of the Sn—Cu binary can be eliminated by the ternary Sn—Cu—Ni. Sn-Cu-Ni or Sn-Ag-
In addition to Cu, Sn-Cu-Ge and Sn-Cu-Al have also been confirmed to be effective.

Example 10 The alloy composition was changed to Sn-5.5G.
The same as Example 1 except that e-4.5Al was used.

Example 11 The alloy composition was changed to Sn-8Ge-
Same as Example 1 except that 7Al was used.

The solidus temperature and liquidus temperature, the rate of change in resistance, the current interruption characteristics (interruption time and temperature), and the flexibility of these examples were measured.

[Table 4] From these examples, it can be seen that the ternary system of Sn-Ge-Al is Sn-Ag-Cu, Sn-Ag-Ge, Sn-Ag-
It is clear that it is as effective as Ni. Other than these, the effectiveness of the ternary system according to claim 1 has been confirmed.

[0034]

According to the present invention, there is provided a fuse element incorporated in an electric component such as a tantalum capacitor.
Stable mounting of electrical components with lead-free solder and prevention of carbonization and burning of electrical components during fuse fusing operation, as well as easy handling of fuse elements and satisfactory wireability. In addition, it is possible to make the fuse element lead-free in the Sn system, which is extremely useful in environmental protection by lead-free.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of a fuse built-in electrical component according to the present invention.

FIG. 2 is a drawing showing a sample for measuring a rate of change in resistance.

[Explanation of symbols]

 a fuse element 1 capacitor element 5 sealing resin layer

Claims (3)

[Claims] 1. A fuse element wherein a multi-element alloy having a liquidus temperature of 300 ° C. to 550 ° C., in which two or more of Ag, Cu, Ni, Ge, and Al are blended with Sn, is processed into a thin wire. . 2. Ag is 5 to 30% by weight, Cu is 1 to 15% by weight, Ni is 0.5 to 5% by weight, Ge is 1 to 10% by weight, and Al is 1 to 10% by weight. Hue described in 1
Element. 3. A fuse element wherein a multi-element alloy which is 5 to 30% by weight of Ag, 1 to 15% by weight of Cu and the balance Sn is processed into a fine wire.