JP2007181880A - Solder, soldering structure, and hole-through ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soldering structure having an inner electrode in the hole inner wall of a structural body, which generates no crack on the interface between the inner electrode and the hole inner wall of the structural body or in the inside of the structural body, which has sufficient strength of the inner electrode, and which is environmentally friendly because of containing no lead; and to provide a hole-through ceramic capacitor having a soldering structure like this. <P>SOLUTION: A soldering structure 1 comprises: a structural body 2 provided with a hole 2a, an inner electrode 3 formed on the inner wall of the hole; a leading wire 4 inserted in the hole; and a solder 5, with which the hole is impregnated, which fastens the leading wire to the inner electrode, and which contains no lead. The solder is made of an alloy whose volume does not shrink during solidification. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a soldering structure in which solder is filled in holes in a structure, and more particularly to a through-type ceramic capacitor.

Conventionally, as a soldering structure having an inner surface electrode on the inner wall of the hole of the structure, for example, there is a soldering structure 21 as shown in FIG. The electrode 3 includes a lead wire 4 inserted into the hole 2a, and solder 15 filled in the hole 2a in order to electrically and mechanically join the inner surface electrode 3 and the lead wire 4. As such solder 15, a solder mainly composed of Sn and Pb, or a solder mainly composed of Sn and Ag, Sn and Cu, or Sn and Sb is used in consideration of the influence on the environment. It has been.
JP 56-133810 A

  However, when the inner surface electrode 3 and the lead wire 4 are joined with the solder 5 in the conventional soldering structure 21, the volume of the solder 5 shrinks when solidified, and the shrinkage stress concentrates on the interface between the inner surface electrode 3 and the inner wall of the hole 2 a. As shown in FIG. 4, there is a problem that a peeled portion 15 a where the inner surface electrode 3 is peeled from the inner wall of the hole 2 a of the structure 2 is generated, or when the structure 2 is brittle, the structure 2 itself is cracked. It was.

  An object of the present invention is to solve the above-described problems. In a soldering structure having an inner surface electrode on the inner wall of a structure body, the interface between the inner surface electrode and the inner wall of the structure body or the inside of the structure body. It is an object of the present invention to provide an environment-friendly soldering structure that does not cause cracks, has sufficient internal electrode strength, and does not contain lead, and a feedthrough ceramic capacitor having such a soldering structure.

  In order to achieve the above object, a soldering structure of the present invention includes a structure having a hole, an inner surface electrode formed on the inner wall of the hole, a lead wire inserted into the hole, and an inner electrode filled in the hole. And solder that does not contain lead to which the lead wire is fixed, and the solder is made of an alloy that does not shrink in volume during solidification.

  Further, the hole in the soldering structure of the present invention is a through-hole penetrating from one surface of the structure to the other surface, the lead wire is inserted into the through-hole, and both ends of the lead wire are led out from both ends of the through-hole. It is characterized by being.

  The feedthrough ceramic capacitor of the present invention includes the soldering structure of the present invention, and the structure is a ceramic sintered body made of a dielectric composition that functions as a capacitor.

  As described above, according to the soldering structure of the present invention, the structure including the hole, the inner surface electrode formed on the inner wall of the hole, the lead wire inserted into the hole, the inner electrode filled in the hole, It is composed of solder that does not contain lead to which the lead wire is fixed, and the solder is composed of an alloy that does not shrink in volume during solidification, so that the interface or structure between the inner surface electrode and the hole inner wall of the structure In this case, no cracks are generated inside the electrode, and it has a sufficient inner surface electrode strength and does not contain lead. Therefore, an environment-friendly soldering structure and a feedthrough ceramic capacitor can be provided.

  An embodiment according to the present invention will be described in detail with reference to FIG. However, the same parts as those in the above-described conventional example are denoted by the same reference numerals, and detailed description thereof is omitted. The soldering structure 1 electrically connects the structure 2 having the hole 2a, the inner surface electrode 3 formed on the inner wall of the hole 2a, the lead wire 4 inserted into the hole 2a, the inner surface electrode 3 and the lead wire 4. It consists of solder 5 which does not contain lead filled in the hole 2a in order to join it mechanically and mechanically. The solder 5 is made of an alloy that does not shrink in volume when the solder is solidified.

  First, an alloy that does not shrink in volume during solidification may be a combination of a metal that expands in volume during solidification and a metal that has a small volume shrinkage. Examples of metals that expand in volume during solidification include Bi and Ga. Is a rare metal, uneasy in terms of stable supply, and expensive, so it is inappropriate as a main component element of a solder material. Therefore, Bi is preferable as the main component of the solder 5.

  Next, the other Bi alone may cause embrittlement, so it is necessary to alloy it to provide toughness.

  Various elements can be added as the element to be added, but considering the characteristics to be provided as solder such as toxicity, supply capability, melting point and solderability, the additive elements are Ag, Au, Cu, In , Sb, Sn, Zn and the like are preferable. The amount of each element added can be adjusted according to the working temperature and required strength, but the alloy composition of the solder 5 is preferably Bi-0.01 to 5 mass% Ag, Bi-0.01 to 25 mass%. Au, Bi-0.01-0.5 mass% Cu, Bi-0.01-57 mass% In, Bi-0.01-5 mass% Sb, Bi-0.01-57 mass% Sn, Bi- It is 0.01-5 mass% Zn.

  In a Bi-Ag alloy, if the eutectic composition of the Bi-Ag alloy, that is, 40% by mass or less, the Bi-Ag alloy expands during solidification, so Ag can be added up to 40% by mass if the working temperature is not restricted. However, Bi-0.01 to 5% by mass Ag is more preferable. If the addition amount of Ag is within 5 mass%, the liquidus temperature of the solder 5 will be 300 degrees C or less, and workability | operativity will be maintained. On the other hand, if the addition amount of Ag is 0.01% by mass or more, an effect of suppressing the brittleness of the solder 5 is obtained, and the bonding strength of the solder 5 is maintained.

In a Bi-Au alloy, if the eutectic composition of the Bi-Au alloy, that is, 39% by mass or less, the Bi-Au alloy expands during solidification, so if the working temperature is not restricted, Au is added up to 39% by mass. However, Bi-0.01 to 25% by mass Au is more preferable. If the added amount of Au is within 25% by mass, the liquidus temperature of the solder 5 becomes 300 ° C. or lower, and workability is maintained.
On the other hand, if the added amount of Au is 0.01% by mass or more, the effect of suppressing the brittleness of the solder 5 is obtained, and the bonding strength of the solder 5 is maintained.

  In a Bi-Cu alloy, if the eutectic composition of the Bi-Cu alloy, that is, 44 mass% Cu or less, the Bi-Cu alloy expands during solidification, so if the working temperature is not restricted, Cu is added up to 44 mass%. However, Bi-0.01 to 0.5% by mass Cu is more preferable. If the amount of Cu added is within 0.5% by mass, the liquidus temperature of the solder 5 becomes 300 ° C. or lower, and workability is maintained. On the other hand, if the amount of Cu added is 0.01% by mass or more, an effect of suppressing the brittleness of the solder 5 is obtained, and the bonding strength of the solder 5 is maintained.

  In the Bi—In alloy, Bi—0.01 to 57 mass% In is preferable. If the amount of In added is within 57% by mass, the solder 5 does not shrink during solidification, and the solder 5 is maintained without being peeled off from the inner surface electrode 3 formed on the inner wall of the hole 2a of the structure 2. On the other hand, when the addition amount of In is 0.01% by mass or more, the effect of suppressing the brittleness of the solder 5 is obtained, and the bonding strength of the solder 5 is maintained.

  In a Bi-Sb alloy, if the eutectic composition of the Bi-Sb alloy, that is, 78 mass% Sb or less, the Bi-Sb alloy expands during solidification, so Sb is added up to 78 mass% if the working temperature is not restricted. However, Bi-0.01 to 5% by mass Sb is preferable. If the amount of Sb added is within 5% by mass, the liquidus temperature of the solder 5 becomes 300 ° C. or lower, and workability is maintained. On the other hand, when the added amount of Sb is 0.01% by mass or more, the effect of suppressing the brittleness of the solder 5 is obtained, and the bonding strength of the solder 5 is maintained.

  In the Bi—Sn alloy, Bi—0.01 to 57 mass% Sn is preferable. If the added amount of Sn is within 57 mass%, the solder 5 does not shrink during solidification, and the solder 5 is kept without peeling from the inner surface electrode 3 formed on the inner wall of the hole 2a of the structure 2. On the other hand, if the added amount of Sn is 0.01% by mass or more, the effect of suppressing the brittleness of the solder 5 is obtained, and the bonding strength of the solder 5 is maintained.

  In a Bi-Zn alloy, if the eutectic composition of the Bi-Zn alloy, that is, 32% by mass or less, the Bi-Zn alloy expands during solidification, so Zn is added up to 32% by mass if the working temperature is not restricted. However, Bi-0.01-5 mass% Zn is preferable. If the added amount of Zn is within 5% by mass, the liquidus temperature of the solder 5 becomes 300 ° C. or lower, and workability is maintained. On the other hand, if the added amount of Zn is 0.01% by mass or more, the effect of suppressing the brittleness of the solder 5 is obtained, and the bonding strength of the solder 5 is maintained.

  The solder composition of the present invention is not particularly limited to the above-described binary solder, and is a solder composition that does not shrink in volume when the solder is solidified, for example, a multi-component solder based on the above-described binary alloy. It does not matter.

  In addition, the soldering method of the solder 5 in the present invention includes, for example, immersion soldering and reflow heating. The soldering structure and the through-type ceramic capacitor of the present invention include the inner surface electrode 3, the lead wire 4, and the solder 5. Any method may be used as long as they can be electrically and mechanically joined to each other.

The structure 2 in the present invention may be a ceramic sintered body made of a ceramic material such as Al ₂ O ₃ or BaTiO ₃ , but is not particularly limited thereto, and can be soldered with metal or resin. Any structure made of a material may be used.

  In addition, examples of the conductive component constituting the inner surface electrode 3 in the present invention include Ag, Ag / Pd, Ag / Pt, Au, Ni, Cu, Al, and the formation method thereof includes sputtering, vapor deposition, and paste. Although the printing method is mentioned, it does not specifically limit and any material and formation method may be used.

  In addition, the lead wire 4 in the present invention uses, for example, a metal wire such as Cu, Fe, Ni, or Au as a core, and if necessary, Sn, Pb, Sn—Pb, Pd, Au, Sn—Cu, Sn— Examples thereof include Ag, Sn—Ag—Cu, Sn—Bi plated, and the like, but any material can be used as long as the composition can be electrically and mechanically joined to the solder 5.

Another embodiment according to the present invention will be described in detail with reference to FIG. The through-type ceramic capacitor 11 is formed on a cylindrical ceramic sintered body 12 made of a dielectric material mainly composed of BaTiO _{3 and} having a through-hole 12a penetrating from one surface to the other surface, and an inner wall of the through-hole 12a. In order to electrically and mechanically join the inner surface electrode 13, the lead wire 14 inserted into the through hole 12a, and the inner surface electrode 13 and the lead wire 14, lead contained in the through hole 12a is not contained. It consists of solder 15 and a surface electrode 16 formed on the surface of the ceramic sintered body 12.

  In addition, as for the material of the inner surface electrode 13, the lead wire 14, and the solder 15, all can select and use the same thing as the inner surface electrode 3, the lead wire 4, and the solder 5 in above-mentioned embodiment. Further, the material and shape of the surface electrode 16 are not limited at all.

  First, solders having the compositions shown in Table 1 were prepared, and these were used as the solders of Examples 1 to 26 and Comparative Examples 1 to 5, respectively.

Next, a cylindrical ceramic sintered body made of a dielectric material containing BaTiO ₃ as a main component and having ₃ mmφ through holes penetrating both end faces is prepared. Next, an inner surface electrode made of Ni was formed on the inner wall of the through hole by electroless plating, and then a lead wire in which Sn was hot-plated with Cu as a core material was inserted into the through hole of the ceramic sintered body and held there In this state, as shown in FIG. 3A, the solders of Examples 1 to 26 and Comparative Examples 1 to 5 are flow soldered at 325 ° C., and the evaluation samples of Examples 1 to 26 and Comparative Examples 1 to 5 are prepared. 100 pieces of each were obtained.

  Then, about the evaluation sample of Examples 1-26 and Comparative Examples 1-5, the generation | occurrence | production condition and joining strength of the crack in the interface vicinity of an inner surface electrode and a ceramic sintered compact were measured, and these were put together in Table 1.

  The crack occurrence rate was determined by observing and judging using a metal microscope after the cross section of the evaluation sample was surfaced with emery paper and mirror-polished with a buff, and the ratio of the evaluation sample in which cracks were observed was determined.

Further, the bonding strength is obtained by cutting the evaluation sample at a position L1-L2 of 3 mm from the side on which the ceramic sintered body is flow soldered as shown in FIG. 3 (b), and as shown in FIG. 3 (c). Was pulled on a perforated holding jig, the lead wire was held with a wedge-shaped chucking jig, and the tensile strength was obtained by pulling the lead wire in the direction in which the solder fillet remains.
The pulling speed was 25 mm / min.

  As is clear from Table 1, the evaluation samples of Examples 2, 3, 6, 7, 10, 11, 14, 15, 17, 18, 24, and 25 all have a crack occurrence rate of 0%. Also, the bonding strength was as high as 111 to 145 N, which was within the most preferable range of the present invention.

  In addition, the evaluation samples of Examples 1, 5, 9, 13, 16, and 23 have a small amount of addition of Ag, Au, Cu, In, Sb, Sn, and Zn, respectively. , 7, 10, 11, 14, 15, 17, 18, 24, and 25, the bonding strength was slightly inferior, but within the practical range and no cracks were generated. Within the scope of the invention.

  On the other hand, the evaluation samples of Examples 4, 8, 12, 19, and 26 have a high liquidus temperature because the added amounts of Ag, Au, Cu, In, Sb, Sn, and Zn are excessive. Moreover, it was not vitrified and could not be evaluated, and was outside the scope of the present invention.

  Moreover, the evaluation samples of Comparative Examples 1 to 5 were all cracked and the bonding strength was 41 to 98 N, which was low and inferior to the above-described examples within the scope of the present invention.

  Further, in Examples 4, 8, 12, 19, and 26, since the liquidus temperature of the solder is high, the solder does not sufficiently melt, the solder does not penetrate into the through hole of the ceramic sintered body, and cracks occur. The occurrence rate and the bonding strength could not be measured, and were outside the scope of the present invention.

It is sectional drawing of the soldering structure of one embodiment which concerns on this invention. The present invention relates to a feedthrough ceramic capacitor which is a soldering structure according to another embodiment of the present invention, wherein (a) is a longitudinal sectional view and (b) is a transverse sectional view. It is explanatory drawing which shows the preparation methods of the evaluation sample for the joint strength measurement in the Example of this invention, (a) is a longitudinal cross-sectional view of flow solder, (b) is a longitudinal cross-sectional view which shows the cutting direction of an evaluation sample (C) is a longitudinal sectional view showing an evaluation method. It is a perspective view of the conventional soldering structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Soldering structure 2,12 Structure 2a Hole 3,13 Inner surface electrode 4,14 Lead wire 5,15 Solder 11 Through-type ceramic capacitor 12 Ceramic sintered body 12a Through-hole

Claims (9)

A solder which is an alloy of Bi and Ag, characterized in that Ag is 0.01 to 5% by mass and the balance is Bi. A solder which is an alloy of Bi and Au, wherein Au is 0.01 to 25% by mass and the balance is Bi. A solder which is an alloy of Bi and Cu, wherein Cu is 0.01 to 0.5% by mass, and the balance is Bi. A solder which is an alloy of Bi and In, wherein In is 0.01 to 57% by mass and the balance is Bi. A solder which is an alloy of Bi and Sb, wherein Sb is 0.01 to 5% by mass and the balance is Bi. A solder which is an alloy of Bi and Zn, wherein 0.01 to 5% by mass of Zn and the balance is Bi. A structure including a hole, an inner surface electrode formed on the inner wall of the hole, a lead wire inserted into the hole, and lead filled in the hole to fix the inner surface electrode and the lead wire A soldering structure, wherein the solder is made of any one of claims 1 to 6. The hole is a through hole penetrating from one surface of the structure to the other surface, the lead wire is inserted into the through hole, and both ends of the lead wire are led out from both ends of the through hole. The soldering structure according to claim 7, wherein: A feedthrough ceramic capacitor comprising the soldering structure according to claim 7 or 8, wherein the structure is a ceramic sintered body made of a dielectric composition functioning as a capacitor.