JP2001332165A - Fuse element and electric component with built-in fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuse element, particularly, a fuse element to be built in electric component including a tantalum capacitor, achieving good Sn-Ag based lead-free formation with the control of the mixing volume of Ag while satisfactorily assuring stable mounting of the electric component with a built-in fuse with lead-free soldering and carbonization and burning prevention of the electric component during fusing operation. SOLUTION: The fuse element built in the electric component to be mounted at 240-320 deg.C comprises a Ag-Sn composition consisting of 10-50 weight % of Ag and Sn in the rest, or 1-10 weight % of Sb added to the Ag-Sn composition consisting of 10-50 weight % of Ag and Sn in the rest.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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. These electronic components with a built-in fuse are heated at the temperature of the fuse element 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. For example, in the case of a tantalum capacitor, smoke of a tantalum powder sintered body is generated. To prevent
It is required to keep the temperature below 600 ° C. The current fuse is of a fast-blow type, in which the fusing current is i, the fusing time is tm, the temperature at the time of fusing of the fuse element is Tm, the resistance is R, and the fuse element is the same. Assuming that the heat capacity per unit length is K and the ambient temperature is θ, almost

The following holds: tm = K (Tm−θ) / Ri ² (1), and Tm is required to be 600 ° C. or less.

The above-mentioned fuse-containing electric parts are usually mounted on a circuit board by a reflow method or a flow method, and the fuse element has a melting point which is not damaged by the temperature at the time of mounting. You need to use

[0004]

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. Thus, the fuse element incorporated in the electric component includes Pb
-Sn, Pb-Sn-Ag, Pb-In, Pb-In-
Ag-based or melting point 2 with Sb, Au, Cu, etc. added to them
An alloy between 60 ° C and 320 ° C was used.

[0005] However, 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 required, and Sn-3.
Lead-free solders such as 5Ag and Sn-0.7Cu have been developed. The mounting temperature using these lead-free solders is higher than that using Pb-Sn solder, and is expected to be 320 ° C. at the maximum. Therefore, the fuse element is also required to be lead-free, and this lead-free is required to prevent the fuse element from being damaged at the time of mounting.
It is required to be able to guarantee the prevention of carbonization and combustion of the electric component body or the mold resin when the fuse is blown.

In the case of Ag-based, Al-based, and Au-based systems, even though overcurrent can be interrupted, it is particularly easy to reduce the thickness of Al.
-Si also has a eutectic temperature of 577 ° C,
It can only barely meet the fusing temperature requirements below. The use of zinc simple solder has also been proposed. However, even if the melting point is 420 ° C. and the above two conditions can be satisfied, the ionization tendency is high and the oxidation is easy, and the vapor pressure is high, so that the heat for electronic parts is high. -Hard to use.

Conventionally, iron having a low thermal conductivity has been used as an electrode material.
Using a nickel alloy or a Kovar alloy, a mold resin having a low thermal conductivity (15 × 10 ⁻⁴ cm ³ / ° C. · sec · cm or less), Sn-5Ag (solidus temperature 221 ° C.) Eutectic point (Ag 3.5% by weight, liquidus temperature 240 ° C.)
A square chip fuse using Sn-Ag near the eutectic point temperature of 221 ° C.) as a fuse element is known (Japanese Patent Laid-Open No. 59-81828), and even when mounted at a temperature of 240 ° C. Because of the low thermal conductivity of electrode materials and mold resin,
It is expected that the device can be mounted without damaging the device. However, such a result cannot be expected at all at a high temperature of about 320 ° C. under the use of the lead-free solder.

The damage process of the fuse element at the time of mounting is such that the melted fuse element is pulled thin by the wetting of the electrodes based on the interfacial energy of the melt, and becomes thin at the end of mounting. The thinning is fixed by the accompanying cooling and solidification. If the thinning immediately before the cooling and solidification is very small, substantial damage can be avoided. Thus, Sn-A shown in FIG.
In the equilibrium diagram of g, in the non-eutectic region, melting starts at a solidus temperature of 221 ° C., and the liquid phase component increases with a further increase in temperature. A phase
If the amount of g is different, even when both solid and liquid coexist at the same temperature, the ratio of the liquid phase is different (therefore, the ratio of the solid component is different), and the interfacial energy of the solid / liquid coexist is reduced. Different.
Therefore, even at the same temperature, the interfacial energy is different between the region near the eutectic point and the region isolated from the eutectic point, and the degree of thinning of the fuse element at the time of mounting, that is, Differences also occur in degree. Therefore, by adjusting the amount of Ag, even if the temperature at which melting starts is the same, the interfacial energy in the solid-liquid coexisting state (semi-molten state) is adjusted.
It is presumed that damage to the fuse element during mounting can be suppressed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuse element, particularly a fuse element incorporated in an electric component such as a tantalum capacitor. While ensuring satisfactory prevention of carbonization and combustion of electrical components during fusing operation, the fuse element S
An object of the present invention is to achieve good lead-free in an n-Ag system by adjusting the amount of Ag. It is still another object of the present invention to provide a fuse element which can be easily processed.

[0010]

A fuse element according to the present invention is a fuse element incorporated in an electric component mounted at a temperature of 240 ° C. to 320 ° C., wherein Ag is 10 to 50% by weight. The composition is characterized in that the balance is an Ag-Sn composition comprising Sn, wherein the temperature of the fuse element at the time of fusing is usually 600 ° C. or less, and the wire diameter is usually 50 μm.
１５０150 μm.

Another fuse element according to the present invention has a temperature of 2
A fuse element incorporated in an electric component mounted at 40 ° C. to 320 ° C., Ag is 10 to 50% by weight, and the balance is S
The composition is characterized in that Sb is added in an amount of 1 to 10% by weight to an Ag-Sn composition consisting of n, and the temperature of the fuse element at the time of fusing is usually 600 ° C. or less, The wire diameter is usually set to 50 μm to 150 μm.

The electric component with a built-in fuse according to the present invention is an electric component mounted at a temperature of 240 ° C. to 320 ° C.
g is 10 to 50% by weight, and the balance contains a fuse element having a composition of Sn.
The temperature of the fuse element at the time of fusing is usually set to 600 ° C. or lower, and the wire diameter is usually set to 50 μm to 150 μm.

Another electric component with a built-in fuse according to the present invention is an electric component mounted at a temperature of 240 ° C. to 320 ° C., wherein Ag is 10 to 50% by weight and the balance is Sn.
A fuse element having a composition in which Sb is added to the Sn composition in an amount of 1 to 10% by weight, wherein the temperature of the fuse element at the time of fusing is usually 600 ° C. or less. And the wire diameter is usually 50 μm to 150 μm. The composition may contain unavoidable impurities.

[0014]

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-mentioned capacitor is mounted on a circuit board by a reflow method or a flow method together with other electric components such as an IC, a transistor, a chip resistor, etc., and a lead-free solder such as Sn-3. 5Ag eutectic (eutectic point temperature 221 ° C), Sn-0.7Cu eutectic (eutectic point temperature 227)
° C), Sn-4Sb (solidus temperature 235 ° C, liquidus temperature 240 ° C), etc., and the mounting temperature is 240 ° C to 320 ° C.
° C. Since the fuse element according to claim 1 of the present invention uses an alloy composition of 10 to 50% by weight of Ag and the balance of Sn, as is clear from the equilibrium state diagram of Sn-Ag shown in FIG. It becomes a semi-molten state at a mounting temperature of 240 ° C. to 320 ° C., becomes a state in which solid particles are mixed in a liquid phase, and has poor wettability. The thinning of the element can be kept slightly, and it can be maintained at almost the original thickness by cooling and solidifying at the end of mounting. Therefore, the above-mentioned fuse built-in capacitor is mounted at a mounting temperature of 240 ° C. to 320 ° C. higher than the solidus temperature of the fuse element.
° C reflow method using lead-free solder or flow
It is possible to mount the fuse element while keeping it stable by the method.

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.
It is required that the fuse element fusing temperature Tm be set to a smoke temperature of 600 ° C. or lower of the tantalum sintered body and tm be as short as possible. Thus, in the fuse element according to the first aspect of the present invention, as will be apparent from the examples described below, under a wire diameter of 50 μmφ to 150 μmφ, 2 to 6 A is cut off for several milliseconds, Further, the overcurrent can be cut off at a temperature of 600 ° C. or less when the fuse element is blown.

In the fuse element according to the first aspect of the present invention, the Ag content is less than 50% by weight.
It has sufficient toughness, and can smoothly supply the fuse element and join it to the electric component without disconnection even under the thin wire diameter of 50 μmφ to 150 μmφ. Also,
The fuse element can be drawn well.
In the fuse element according to claim 1 of the present invention, Ag is used.
The addition amount was set to 10% by weight or more, and Sn-
As is clear from the Ag equilibrium state diagram, even if the amount of Sn is slightly increased, the fluctuation of the liquidus temperature can be suppressed to a small extent. Melting point characteristics can be sufficiently maintained. The fuse element according to the present invention can also be used in a form in which a single fuse element is mounted on a fuse electrode of a circuit board by the above-mentioned reflow method or flow method. Further, 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.

The fuse element according to claim 1 of the present invention comprises:
It can also be manufactured by spinning in a rotating liquid. That is, a molten jet injected from a nozzle is made 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. Spinning can also be performed by rapid cooling and solidification in a cooling liquid layer. 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 wire diameter of 50 μmφ to 150
A fuse element having a fine line of μmφ can be easily manufactured.

According to the fuse element of the second aspect of the present invention, the Ag-Sn of the fuse element of the first aspect is provided.
A composition in which Sb is added to the composition (Ag is 10 to 50% by weight, the balance being Sn) and Sb is added to 1 to 10% by weight. The addition of Sb enhances the toughness and draws a thin wire having a wire diameter of 50 μm to 150 μm. In addition, the wire breakage resistance at the time of coil removal by spinning in a rotating liquid is enhanced to further facilitate the production of fine wires. The reason why the addition amount of Sb is 1 to 10% by weight is as follows.
If the amount is less than 10% by weight, the effect of improving the toughness is not obtained.
This is because it becomes difficult to enjoy the advantages based on the weight% and the balance Sn). This fuse element can also be used by being incorporated in an electric component such as a tantalum capacitor.

[0020]

[Example 1] A drum having an inner diameter of 500 mm and a width of 45 mm was rotated at 200 rpm to form about 1600 ml of water in a layered form. By pressurizing with nitrogen gas, spinning was performed by jetting a jet from a quartz glass nozzle as a jet at the same speed as the peripheral speed of the cooling liquid layer to produce a Sn-15Ag 140 μmφ fine wire, which was used as a fuse element. The fuse element has a solidus temperature of 221 ° C. and a liquidus temperature of 340 ° C.

[Embodiment 2] In the same manner as in Embodiment 1, Sn
A 90 μmφ thin wire of −35 Ag was manufactured and used as a fuse element. The solidus temperature of this fuse element is 221.
° C and the liquidus temperature is 430 ° C.

[Embodiment 3] In the same manner as in Embodiment 1, Sn
A 110 μmφ fine wire of −50 Ag was manufactured and
Element. The solidus temperature of this fuse element is 221.
℃, liquidus temperature is 490 ℃.

Example 4 An extruded wire of Sn-20Ag-6Sb was processed into a thin wire of 80 μmφ by die drawing, and this was used as a fuse element. The fuse element has a solidus temperature of 230 ° C. and a liquidus temperature of 380 ° C.

Comparative Example 1 In the same manner as in Example 1, Sn
A 110 μmφ fine wire of −5 Ag was manufactured and used as a fuse element. The solidus temperature of this fuse element is 221.
° C and the liquidus temperature is 240 ° C.

Comparative Example 2 In the same manner as in Example 1, Sn
A 90 μmφ fine wire of −55 Ag was manufactured and used as a fuse element. The solidus temperature of this fuse element is 221.
° C and the liquidus temperature is 520 ° C.

The following resistance value change rates and current interruption characteristics (interruption time and temperature) of these examples and comparative examples are as follows.
The measured flexibility and flexibility were as shown in Table 1 (average value of 20 samples).

[Rate of change in resistance value] This is for evaluating the possibility of mounting at a temperature of 280 ° C. As shown in FIG. 3, counter electrodes 62 and 62 are provided by applying and firing Ag paste on a ceramic substrate 61, a fuse element a is placed between the electrodes, and tin-plated copper is further provided on each electrode 62. The wire 63 was welded, and the sample welded between each electrode and the fuse element a by the welding heat was kept at 280 ° C. for 10 minutes in the atmosphere.
The rate of change in resistance value with respect to the initial time at 0 minutes was measured. The reason why the tin-plated copper wire 63 is provided is that the melted fuse element is apt to be wet and a strict evaluation is performed. [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] A sample which was wound around a rod having a diameter of 0.5 mm and did not break was evaluated as ○, and a sample which was broken was evaluated as ×.

[0028]

Table 1 Current interruption characteristics Alloy composition Resistance change rate (%) Interruption time Fusing temperature Flexibility Example 1 Sn-15Ag +0.64 0.060 seconds 350 ° C ○ Example 2 Sn-35Ag +2.100 0.0015 seconds 500 ° C ○ Example 3 Sn-50Ag -0.99 0.090 seconds 530 ° C ○ Example 4 Sn-20Ag6Sb -3.5 0.014 seconds 380 ° C ○ Comparative Example 1 Sn-5Ag measurement impossible 0. 050 seconds 300 ° C ○ Comparative example 2 Sn-55Ag -0.76 0.120 seconds 540 ° C ×

In the fuse element according to the present invention, the melting start temperature (solidus temperature 221.degree. C.) is 320.degree.
Even if the temperature is lower, the liquidus temperature is 320 ° C. or higher, and the liquidus does not completely liquefy under the temperature of 320 ° C. and becomes a semi-molten state. Even if an electric component incorporating the fuse element according to (1) is mounted at a high temperature of 320 ° C., the fuse element can be stably held without substantial thinning. This means that the resistance change rate of Comparative Example 1 was not measurable (the fuse element was melted and the resistance value rise was extremely large), whereas the resistance change rates of Examples 1 to 4 were very small. It can be confirmed from that.

Further, in the fuse element according to the present invention, the liquidus temperature is sufficiently lower than 600 ° C., and the temperature of the fuse element at the time of fusing can be suppressed to 600 ° C. or less, so that electric parts and sealing can be prevented. The fact that carbonization and combustion of the resin can be prevented can also be confirmed from the temperature at the time of fusing of the current interruption characteristics in Table 1.

Furthermore, the fuse element according to the present invention is excellent in flexibility, and can sufficiently prevent bending breakage during supply and bonding to an electric component, from the evaluation of flexibility in Table 1. You can check. In particular, the fuse according to claim 2.
In the size element, the toughness of the composition is further enhanced by adding Sb within a range that can maintain the above-mentioned advantage sufficiently.
It is possible to further facilitate the production of fine wires of 50 μmφ to 150 μmφ.

[0032]

According to the present invention, in a fuse element, in particular, in a fuse element incorporated in an electric component such as a tantalum capacitor, the electric component having a built-in fuse can be stably mounted with lead-free solder and the fuse can be incorporated. Prevents carbonization and combustion of electrical components during the fuse fusing operation, and further ensures that the fuse element is easy to handle and easy to manufacture. Freezing can be enabled, and lead free is extremely useful for environmental protection.

[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 an equilibrium diagram of a Sn—Ag alloy.

FIG. 3 is a drawing showing a measurement sample of a resistance change rate.

[Explanation of symbols]

 a fuse element 1 capacitor element 5 sealing resin layer

Claims (6)

[Claims] 1. A fuse element incorporated in an electric component mounted at a temperature of 240.degree. C. to 320.degree.
A fuse element having an Ag-Sn composition of 0% by weight and the balance of Sn. 2. A fuse element incorporated in an electric component mounted at a temperature of 240.degree. C. to 320.degree.
0 to 10% by weight of Sb is added to an Ag-Sn composition comprising 0% by weight and the balance Sn.
Element. 3. The fuse element according to claim 1, wherein the temperature of the fuse element at the time of fusing is 600 ° C. or less. 4. The fuse element according to claim 1, wherein the wire diameter is 50 μmφ to 150 μmφ. 5. An electric component mounted at a temperature of 240.degree. C. to 320.degree. C., wherein a fuse element having an Ag-Sn composition composed of 10 to 50% by weight of Ag and the balance of Sn is incorporated. Fuse built-in electrical parts. 6. An electrical component mounted at a temperature of 240 ° C. to 320 ° C., wherein Ag is 10 to 50% by weight, and the balance is Sn-Ag-Sn composition in which Sb is added at 1 to 10% by weight. An electronic component with a built-in fuse, comprising the fuse element of (1).