JP2007075897A - Lead-free solder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead-free solder which is free from harmful substances and excellent in solderability. <P>SOLUTION: The lead-free solder contains 30-60 wt.% zinc, 0.1-2 wt.% copper and the balance of tin, or contains 30-60 wt.% zinc, 0.1-2 wt.% copper, 0.1-1 wt.% nickel and the balance of tin. Either of the above-mentioned solders further may contain 0.01-0.5 wt.% aluminum. The invented solder is used for soldering electronic components or connecting fuse wires. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lead-free solder suitable for use in assembling electronic components and electronic devices, for example.

  Conventionally, tin-lead solder has been used for surface mounting of small electronic components on printed circuit boards and the like, and for manufacturing and assembly of electronic devices. However, since this type of solder contains lead that is not only harmful to the human body, but also leads to environmental destruction, it is possible for the electronics industry to realize solder that does not contain lead, which is a harmful substance. Various lead-free solders have been proposed in response to such demands.

  For example, Patent Document 1 describes a lead-free solder alloy composed of 7 to 10 weight percent zinc (Zn), 0.01 to 1 weight percent nickel (Ni), and the balance tin (Sn). In addition, the solder material disclosed in Patent Document 2 has been made in view of environmental problems after discarding electronic equipment, and tin, 3 to 18 weight percent zinc with respect to the tin, and a small amount It is a lead-free solder material containing an additive component (for example, nickel).

Japanese Patent Laid-Open No. 9-94688 JP 2000-15478 A

  The tin-zinc-nickel lead-free solder described above is an environment-friendly solder that does not contain lead. However, from the viewpoint of solder properties, the problem of poor workability and wettability, and appropriate There is also a problem that a good solder fluidity cannot be obtained. For example, when this kind of lead-free solder is used inside a component when mounting an electronic component on the board, the solder inside the component melts due to reflow when mounting the board, causing the fuse element to break, etc. There is a problem that quality cannot be maintained.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to use lead-free solder that is suitable for use in electronic equipment and electronic components and has no influence on the environment including the human body. Is to provide.

  As one means for achieving the above-described object, the present invention has the following configuration, for example. That is, the lead-free solder according to claim 1 is characterized by containing 30 to 60 weight percent zinc, 0.1 to 2 weight percent copper, and the remaining weight percent tin.

  The lead-free solder according to claim 2 comprises 30 to 60 weight percent zinc, 0.1 to 2 weight percent copper, 0.1 to 1 weight percent nickel, and the remaining weight percent tin. It is characterized by containing.

  The lead-free solder according to claim 3 further contains 0.01 to 0.5 weight percent of aluminum with respect to the lead-free solder. The lead-free solder according to claim 4 is characterized in that the lead-free solder is soldered in an oxygen atmosphere.

  As described above, according to the present invention, it is possible to provide lead-free solder that has no adverse environmental impact due to harmful substances and is excellent in properties such as solderability on the substrate.

  Embodiments according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an exploded configuration diagram of a chip-type fuse according to the present embodiment. The chip-type fuse shown in the figure has a structure in which a fuse is stretched in the hollow of a ceramic base, and this base is formed by fitting a ceramic case body 2 and a ceramic lid 3. Is done.

  An opening 9 that opens toward the upper surface is provided at the center of the case body 2, and recesses 11 that communicate with the opening 9 are provided at both ends of the case body 2.

  A groove 8 is formed on the bottom surface of each recess 11. A fuse wire (fuse element) 1 that is a fusible body is aligned with the groove 8 and stretched across the opening 9.

  When the fuse wire 1 is stretched between the recesses 11, a certain tension is applied to the fuse wire 1. To maintain the tension, for example, the fuse wire 1 is inserted into the groove portion 8 with resin or the like. May be temporarily fixed.

  Thus, the lid 3 is fitted (casing) in the opening 9 of the case body 2 on which the fuse wire 1 is stretched. The lid 3 has a shape in which both end portions 13 are fitted in the concave portion 11 (a shape in which the width and depth of the end portion 13 are slightly smaller than those of the concave portion 11). The center part of the cover has a shape that covers the opening 9 almost completely (the length and width of the cover center part are slightly smaller than that of the opening 9).

  In this manner, the base body in which the case main body 2 and the lid 3 are combined has a substantially rectangular parallelepiped shape. The appearance of the fuse at that time is shown in FIG. As shown in FIG. 2, when the case main body 2 and the lid 3 are combined, the bent portion 1D of the fuse wire 1 is projected from the end of the base. The bent portion 1D is connected to a metal cap as will be described later.

  The metal cap (electrode) 4 is made of, for example, a copper material or a copper alloy material, and is placed on one side of the cube (a surface facing the base) so that it can be placed on the end of the base in the state shown in FIG. Has an open shape. Further, before the electrodes 4 are put on the end portions of the substrate, solder pieces 5 having the composition described later are inserted into the interiors 6 of the respective electrodes 4 (see FIG. 1). And the electrode 4 in which the solder piece 5 was inserted is put on the both ends of a base | substrate (it press-fits).

  The supply of solder to the inside 6 of each electrode 4 is not limited to a solder piece, but a method of supplying molten solder or cream-like solder into a cap instead of the solder piece. It may be.

  FIG. 3 shows the appearance of the fuse when the electrode 4 is covered in this way. For the fuse in this state, as shown in FIG. 1, the portion (heating position) 7 indicated by the hatched portion of the electrode 4 is heated by a heater, for example, at 350 ° C. for about 3 seconds, so that the electrode 4 The solder piece 5 inserted in the inside of the metal melts.

  As a result, the solder piece 5 is soldered (fused) to the bent portion 1D of the fuse wire 1 described above, and the fuse wire 1 and the electrode 4 are electrically connected.

  The shape of the case body 2 and the lid 3 of the chip-type fuse according to the present embodiment is set so that the outer dimension of the lid 3 is slightly smaller than the inner dimension of the case body 2 as described above. . Therefore, those positions are easy to align, and the lid 3 is inserted into the case body 2 in the vertical direction during assembly, so that they are fitted.

  Therefore, in a state where the case main body 2 and the lid 3 are fitted, the end portion 13 of the lid 3 does not protrude from the concave portion 11 of the case main body 2, and the press-fitting of the electrode 4 to the base end portion is smoothly performed. In addition, the electrical connection between the fuse wire 1 and the electrode 4 can be ensured.

  When the lid 3 and the case main body 2 are fitted, they are bonded together with, for example, an adhesive such as epoxy, and heated for a certain period of time (for example, at 150 ° C. for about 15 minutes). Then, after the adhesive is cured, the electrode 4 is press-fit.

  Further, the electrode 4 of the chip-type fuse according to the present embodiment is also a place to be soldered to the land pattern of the mounting board when mounted on the printed board. Therefore, although not shown in the drawing, the dimensions of the electrode 4 are, for example, one of the four surfaces around the press-fitted electrode 4 for easy and reliable soldering to the board when the fuse is mounted. However, the thickness of the electrode 4 protrudes from the base surface of the chip-type fuse. The other three surfaces around the electrode 4 are aligned with the base surface of the chip-type fuse (become the same surface).

  Thus, by flattening the surface positions of the electrode 4 and the base body, for example, a vacuum chuck when mounting a chip-type fuse on a printed circuit board becomes easy, and the stamping operation on the fuse body is also possible. Easy to do.

  Next, the solder piece used for the chip-type fuse according to the present embodiment will be described in detail.

  In the fuse according to this embodiment, tin / zinc high-temperature solder is used as the solder piece used for connecting the fuse wire. The solder heat resistance (rate of change in resistance value) was measured when the content of zinc (Zn), which is considered appropriate as the content of zinc, was 30 to 60 weight percent. An example of the measurement result is shown in FIG.

  For comparison, the characteristic of a conventional tin-lead solder (containing 90 weight percent lead) is shown in the right end portion of FIG. In FIG. 4, the number shown before Zn is the content of zinc (Zn).

  As the ratio of tin (Sn) and zinc (Zn), the higher the ratio of zinc (Zn), the higher the melting point and the higher the solder heat resistance. However, when the ratio of zinc (Zn) is too large, the processing becomes difficult. . On the other hand, if the proportion of zinc (Zn) is too small, the fluidity increases and the solder heat resistance decreases.

  As shown in FIG. 4, even if the above conditions are taken into consideration, a tin / zinc-based high-temperature solder containing 30 to 60 percent by weight of zinc can be sufficiently put into practical use.

  Specifically, lead-free (lead-free) composed of 30 to 60 weight percent zinc, 0.1 to 2 weight percent copper, 0.1 to 1 weight percent nickel, and the remaining weight percent tin Use solder.

  Or lead-free (lead-free) solder composed of 30 to 60 weight percent zinc, 0.1 to 2 weight percent copper and the remaining weight percent tin, or 30 to 60 weight percent zinc, nickel A lead-free (lead-free) solder having a composition containing 0.1 to 1 wt.% Of tin and the remaining weight percent of tin is used.

  Thus, tin / zinc / nickel or tin / zinc / copper suitable for current fuses and having a solid phase temperature of 199 ° C. and a liquid phase temperature of 360 ° C. or higher by containing 30 to 60% by weight of zinc. It becomes the solder of the system.

  By the way, tin / zinc / nickel or tin / zinc / copper solder has fluidity due to reheating such as reflow when mounting a chip type fuse on a printed circuit board, so the air inside the chip type fuse expands. Therefore, there is a possibility that troubles such as flushing of solder may occur. For this reason, it is necessary to reduce the fluidity of the solder.

  Since aluminum has a low specific gravity, it solidifies on the surface of the joint when melted. Furthermore, since it is easy to oxidize, a strong oxide film is formed on the joint surface. For this reason, when the fuse reaches an open circuit state, the insulation is enhanced and the arc is extinguished.

  Moreover, since there is an effect of reducing the fluidity of the solder, 0.01 to 0.5 weight percent of aluminum is added to the solder in this embodiment.

  However, if the added amount of aluminum is less than 0.01 weight percent, the influence on the fluidity is small and there is no predetermined effect. On the other hand, if the added amount is more than 0.5 weight percent, the conductivity is lowered due to oxidation of aluminum when left at high temperature. In view of the above, in the present embodiment, the amount of aluminum added is set to a very small amount within the range in which fluidity is effective, and the amount added is set according to the solder use conditions.

  Thus, by containing 30 to 60 weight percent of zinc, a solid phase temperature suitable for a current fuse can be obtained, but 40 weight of zinc whose characteristics such as heat resistance are equivalent to those of a conventional tin-lead solder. It is preferable to use a tin-zinc solder containing a percentage. Therefore, in this embodiment, the current fuse uses a tin-zinc solder containing 40 weight percent zinc.

  Table 1 shows the evaluation results when the content ratios of copper, nickel, and aluminum contained in the tin-zinc solder are changed.

  Here, “workability” is workability such as when a solder joint is put into an electrode cap, and if it is moderately soft, it is preferable because it fits the inner surface of the electrode cap. Also, “solder manufacturability” is workability when a joint is manufactured by melting a solder material.

  “Heat resistance” is a change in resistance value accompanying a change in temperature, and “wetability” is the adherence of solder to the bonding target. If the wettability is poor, the solder peels off on the surface of the bonding target.

  FIG. 5 is a graph showing a comparison in resistance value change between the fuse using the solder according to the present embodiment and the fuse using the conventional solder. As the solder according to the present embodiment, here, a solder containing 40% by weight of zinc, 1% by weight of copper, 0.5% by weight of nickel and the remaining weight percent of tin is used. A performance test was conducted using 10 weight percent and 90 weight percent lead.

  The test conditions here are the rate of change in resistance value when immersion is repeated 5 times in molten solder at 260 ° C. for 10 seconds. As can be seen from FIG. 5, the solder according to this embodiment is used. In the case of the used fuse, the change in resistance value is 2% or less at maximum. This is substantially the same characteristic as a fuse using conventional lead-containing solder (indicated by a dotted line in the figure).

  The reason why such characteristics are obtained is considered to be as follows. That is, the solder according to the present embodiment has low fluidity in a solid-liquid coexistence state, and even when heated when mounted on a printed circuit board, the shape of the solder (joint) connecting the fuse and the electrode does not change, The connection state is maintained.

  This is because the solder according to the present embodiment is soldered in an oxygen atmosphere, the surface is stably oxidized by the heat at that time, and a strong oxide film is formed. This is due to the decline.

  In addition, since the joint by solder according to the present embodiment is shielded from oxygen by a special flux, the oxidation of the joint of the solder may not proceed after that once soldering is performed. This is one of the reasons why the above characteristics can be obtained.

  As described above, according to the present embodiment, before the electrode is press-fitted into the end portion of the fuse base, a solder piece is put in the electrode in advance, and heat is applied from the outside of the electrode, By melting the solder, it is possible to reliably connect the electrode and the fuse wire, and it is possible to satisfactorily maintain the electrical joining state at the joint.

  In addition, by using tin / zinc / nickel solder that does not contain lead or other harmful substances as solder pieces used for connecting to the fuse wire inside the electrode, soldering can be performed in an environment or human environment. In addition to avoiding adverse effects on the health of the device, and adversely affecting other electronic components mounted together with the current fuse, the internal state of the current fuse can be maintained even if the substrate is overheated.

  Furthermore, by adding aluminum as a solder material alloy, the heat resistance and fluidity of the solder can be improved, thereby improving the solderability and preventing changes in the joint shape of the solder due to reheating. .

  Further, in the fuse according to the present embodiment, by heating the electrode at 350 ° C., sufficient bonding between the electrode and the fuse wire can be obtained. It was found that soldering was completed at a temperature below the phase temperature. Therefore, soldering can be performed even in a solid-liquid coexistence state between the solid phase temperature and the liquid phase temperature, and deterioration of plating on the electrode surface can be suppressed.

  The composition of the lead-free solder described above may contain inevitable impurities as indicated by Japanese Industrial Standards (JIS) or the like. However, even when such inevitable impurities are contained in the lead-free solder, it does not depart from the scope of the claims of the present invention.

1 is an exploded configuration diagram of a chip type fuse according to an embodiment of the present invention. FIG. It is a figure which shows the external appearance of the current fuse which has a base | substrate which united the case main body and cover which concern on the example of this Embodiment. It is a figure which shows the external appearance of the current fuse when the electrode which concerns on the example of this embodiment is covered. It is a figure which compares and shows the resistance value change of the fuse which uses the tin / zinc-type solder at the time of changing the content rate of zinc which concerns on the example of this Embodiment. It is a figure which compares and shows the resistance value change of the fuse which uses the solder which concerns on this Example, and the fuse which uses the conventional solder.

Explanation of symbols

1 Fuse wire (fuse element)
2 Case body 3 Lid 4 Cap (electrode)
5 Soldering piece 7 Heating position 9 Opening 8 Groove 11 Recess

Claims (4)

A lead-free solder comprising 30 to 60 weight percent zinc, 0.1 to 2 weight percent copper, and the remaining weight percent tin. A lead-free solder comprising 30 to 60 weight percent zinc, 0.1 to 2 weight percent copper, 0.1 to 1 weight percent nickel, and the remaining weight percent tin. The lead-free solder according to claim 1 or 2, further comprising 0.01 to 0.5 weight percent of aluminum. The lead-free solder according to claim 1, wherein the lead-free solder is soldered in an oxygen atmosphere.

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