JPH0821666B2 - Lead pin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lead pin used for an external terminal or the like of an IC ceramic package.

(Prior Art) Conventionally, as a lead pin used as an external terminal of an IC ceramic package, there is known one in which a silver solder for brazing the lead pin to an electrode of the package is previously joined to one end of a lead pin body. . The lead pin to which such a silver solder is joined is manufactured as follows. As shown in FIG. 9, with the silver brazing piece 13 placed on the top surface 11a of the head of the lead pin body 11,
After these are set on the refractory jig 15, they are heated to a temperature equal to or higher than the melting point of the silver solder to melt the silver solder piece 13. After that, the molten silver solder is solidified to form a silver solder portion 17 on the upper surface 11a of the lead pin body 11 as shown in FIG. 10, whereby the lead pin 19 is obtained.

(Problems to be Solved by the Invention) However, the lead pin manufactured through the step of melting the silver solder as described above has the following problems.

(1) When a piece of silver solder is melted by heating it above its melting point, the molten silver solder spreads in a bowl shape on the top surface 11a of the head of the lead pin body due to its surface tension, as shown in FIG. Ideally, the height should be constant. However, in reality, even if careful attention is paid to process control such as strict temperature control, part of the molten silver solder will vibrate and other factors, causing the upper surface of the head of the lead pin body to rise.
It overflows from 11a. For example, as shown in FIG.
The melted silver solder 17a flows to the outer peripheral surface 11b of the head portion of the lead pin body or, as shown in FIG. 12, wraps around the lower head portion 11c of the lead pin body. As a result, it is difficult to form an amount of silver brazing part sufficient for the main brazing at the time of mounting the lead pin, and the silver brazing consumed to form a sufficient silver brazing part. Is unnecessarily large, the height of the brazing portion is also varied, and as a result, the total length of the lead pin is varied, which is inconvenient during mounting.

(2) As mentioned above, when the molten silver brazing material wraps around the underside of the head of the lead pin body and solidifies there (see Fig. 12), the diameter of the lead pin body is reduced by the amount of the attached silver brazing material. Becomes thicker. It is difficult to detect such adhesion of silver brazing to the underside of the head, and if such a lead pin is used as it is, it is possible to fix the lead pin to a fixing jig that fixes the lead pin during brazing assembly. There is a problem that you cannot do it. Such an adverse effect becomes a serious adverse effect when automating the brazing and assembling work.

In addition, the silver brazing material attached to the unnecessary portion as described above causes so-called stress cracking, in which, when stress is applied to the portion at the time of mounting, it penetrates into the crystal grain boundaries of the texture of the portion and causes cracks therein. This may cause breakage of the lead pin, which may cause a serious defect in the mounting package.

(3) When the silver solder is once heated to a temperature equal to or higher than the melting point and then melted and solidified as in the conventional case, the fluidity of the silver solder tends to decrease when heated again. Especially, it is often used for external terminals of ceramic packages. It is remarkable in the silver-copper binary wax. That is, in the case of the conventional product, the excellent "wetting" property and the throwing power inherent to the silver brazing are hindered during the main brazing.

Then, in order to solve such a problem of the prior art, it is conceivable to use a diffusion bonding method or the like to bond the silver brazing member to the lead pin body without melting.

In this method, since the silver brazing member is not completely melted, the height of the silver brazing member joined to the lead pin body is as follows when the silver brazing member is placed on the lead pin body.
It is almost determined by the height of the silver brazing member.
Therefore, when using a silver brazing member having a different height depending on how to place it, the silver brazing member must always be placed on the lead pin in a correct posture. However, in the work of mounting the silver brazing member on the lead pin body, it is difficult to control so that the silver brazing member is mounted in the correct posture for each lead pin. The silver brazing member on the lead pin body may be oriented in an incorrect direction due to vibration applied between the two.

An object of the present invention is to solve such a problem.

(Means for Solving the Problems) In order to achieve the above object, in the lead pin of the present invention, one end surface of the lead pin body does not completely melt the silver brazing member, The original shape of the silver brazing member is bonded as it is, and the shape of the silver brazing member does not change substantially depending on how it is mounted on the lead pin body. In the present invention, as the shape of the silver brazing member, a cube having the same length on each side or a cylindrical shape having the same diameter and height is used.

(Operation) In the lead pin of the present invention, the silver brazing member joined without being melted has a shape such that the heights thereof are substantially the same regardless of how the silver brazing member is placed on the lead pin body. . Therefore, even when the attitude of the silver brazing member is not controlled in the step of mounting the silver brazing material, and even if the attitude of the silver brazing material placed before the bonding step is changed, the silver brazing material after the bonding is completed. There is no variation in member height.

Further, when the silver brazing member is joined to the lead pin body, the silver brazing member does not substantially melt, and therefore the original shape is kept almost the same, and it does not melt like the conventional method. It does not flow down from the top surface of the top of the body, and all of the silver brazing material is used for the main brazing (bonding with the electrode during packaging), and it is also possible to melt unnecessary silver brazing material. Since there is no wraparound phenomenon based on this, it is possible to avoid stress cracking due to silver brazing that has occurred in the conventional lead pin legs and the like. Further, when the silver brazing material is joined to the lead pin body without melting and solidifying, the silver brazing material retains the fluidity of the body as it is, and when the heating temperature exceeds the predetermined value during the main brazing. At the same time, flow occurs, and brazing is reliably performed without impairing the original characteristics of brazing.

This point will be described by taking a silver-copper binary solder as an example. The structure of this binary wax is α rich in silver and β rich in copper.
Phase and (α + β) phase, and shows a substantially uniform structure by repeating the composition processing and annealing until the product. Therefore, when heated, melting starts at a melting point determined by the composition ratio of silver and copper, and at the same time when the pour point is reached, flow starts rapidly. However, as in the case of the conventional silver brazing clad lead pin, the brazing structure that has once undergone melting and solidification has an α phase rich in silver and a β rich in copper.
The phase and the (α + β) phase become a clearly separated macroscopic mixture. Therefore, melting starts from a eutectic composition phase and then gradually progresses to a phase with a high melting point, so that it begins to flow later in time as compared with the unmelted wax described above, and it is extremely high. Progress slowly. As a result, the fluidity and wettability of the solder are poor, and the probability of occurrence of brazing defects increases. On the other hand, since the wax attached to the lead pin body by the method of the present invention has a uniform structure, the flowability and wettability are maintained in a suitable state.

(Effect of the Invention) As described above, according to the lead pin of the present invention, the height of the silver brazing member after joining is substantially the same even if the placement of the silver brazing member on the lead pin body is different for each lead pin. Since it is held at a constant value, it is possible to manufacture a lead pin with silver brazing having no variation in dimensions.

In addition, since the silver brazing member is joined to the lead pin body without substantially undergoing melting and solidification, the conventional drawback is that molten silver brazing material flows from the top surface of the top of the lead pin body and adheres to unnecessary portions. It is possible to avoid various adverse effects caused by this, there is little variation in the entire lead pin, automation at the time of mounting is performed with high yield, and there is an advantage that silver brazing can be saved, as well as the above-mentioned stress cracking. It is possible to avoid a serious accident called fracture. Further, the structure of the silver brazing member remains substantially in a uniform state before its attachment, and the main brazing can be performed while maintaining the fluidity and wettability of the silver brazing material in good condition. Suitable brazing can be achieved.

Further, the shape of the silver brazing member of the present invention can be easily obtained by cutting from a wire rod having a square cross section or a wire rod having a circular cross section, so that it can be manufactured easily and can be manufactured at a low cost.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 8.

FIG. 1 is a diagram showing an example of a lead pin manufactured by the method of the present invention. As shown in the figure, the lead pin 1 is composed of a lead pin body 3 and a silver brazing member 5, and has a structure in which the silver brazing member 5 is diffusion-bonded to the top surface 31b of the lead pin body 3.

As shown in FIG. 2, the lead pin body 3 includes a disk-shaped head portion 31 and a cylindrical leg portion 33 coaxially formed on the lower surface 31a. To give an example of the dimensions of each part, the above head has a diameter of 0.75 mm and a thickness of 0.2 mm.
The leg has a diameter of 0.44 mm and a leg length of 4.5 mm.
Is. The lead pin body having such a shape is made of Kovar.

As shown in FIG. 3, the silver brazing member 5 is obtained by cutting from a wire 51 having a square cross section, and has a substantially cubic shape. Therefore, whichever surface is joined to the lead pin body 3, the height from the top surface 31 of the lead pin body is the same. That is, as shown in FIG. 1, this silver solder is used even when the surface 5a is joined to the top upper surface 31b of the lead pin body and when other surfaces such as the surface 5b are joined to the top upper surface 31b. There is no change in the height of the member. The silver brazing member is sized to fit within the top surface of the top of the lead pin body. For a lead pin body having the above dimensions, one side of the silver brazing member may be 0.46 mm. The silver brazing material is made of 85 silver-copper alloy.

Next, a process of joining the lead pin body 3 and the silver brazing member 5 will be described. First, on the top surface 31 of the lead pin body 3,
Place the silver brazing member 5. Here, in this mounting work, the attitude of the silver brazing member 5 is not controlled, and a method of simply dropping the silver brazing member 5 from above is used. Next, as shown in FIG. 4, the lead pin body 3 with the silver brazing member 5 mounted thereon is
Set in a fire resistant jig 7. After that, these are placed in an atmosphere furnace in which the mixing ratio of nitrogen and hydrogen is adjusted to 5: 1 and heated at 760 ° C. for 10 minutes. In this manner, the original shape of the silver brazing member 5 is kept almost unchanged, and the silver brazing member 5 is diffusion-bonded to the upper surface 31b of the top portion of the lead pin body without melting.

In the lead pin of this example manufactured in this manner, the height of the joined silver brazing member was constant in each lead pin, and there was almost no variation in the total length of the lead pin, which was suitable.

Here, the lead pin formed by the above method,
The fluidity with a conventional silver brazing lead pin having a silver brazing portion formed by melting was compared by measuring the fillet height. That is, five lead pins having the above-mentioned size are used as the lead pins of the present invention, and five lead pins having the same amount (about 1 milligram) of silver solder as the silver solder clad lead pin of the present invention are also used as conventional examples. Then, as shown in FIG. 5, the fillet height H when these lead pins A were brazed to the nickel plate B was measured.

 The results of this comparison are shown in the table below.

As is clear from the above table, the fillet height of the present invention is more than twice as high as that of the conventional one, and the fluidity of the silver brazing material is maintained in a better state.

Next, FIGS. 6 to 8 show examples of the shapes of silver brazing members used in other examples and comparative examples of the present invention. Of these, the silver brazing member shown in FIG. 6 is a regular tetrahedron, and in order to obtain a silver brazing member of about 1 milligram as in the above embodiment, the length of one side may be 0.73 mm.
Further, the silver brazing member shown in FIG. 7 has a spherical shape, and the diameter thereof may be set to 0.57 mm to obtain a silver brazing member of about 1 milligram. The examples shown in FIGS. 6 and 7 are comparative examples, and are difficult to manufacture due to the peculiarity of the shape as compared with the silver brazing member of the present invention, and are not practical. FIG. 8 shows another embodiment of the present invention. The silver brazing member shown in FIG. 8 is a cylinder whose outer diameter d and height h are the same. Even with such an equiaxed cylinder having the same diameter, the height of the silver brazing member can be made constant regardless of how to place it on the lead pin body. In order to obtain about 1 gram of silver brazing material in this cylinder, its outer diameter and height are about 0.5 mm.
And it is sufficient.

In addition, the above-mentioned example shows an example of the size and composition of each part, and is not intended to limit the present invention thereto. In particular, the shape of the silver brazing member, which is one of the features of the present invention, is not limited to the shape of each of the above-mentioned examples, as long as the height of the silver brazing member does not change depending on the posture in which it is placed. Of course, it may have any shape.

In addition, for the joining of the silver brazing material, it is possible to use spot welding, ultrasonic welding, etc. in addition to the heating below the melting point of the silver brazing material in vacuum or atmosphere as described in the present embodiment. Even by the method, the original shape at the time of supplying the silver brazing material can be substantially maintained, and the bonding can be achieved while the structure of the silver brazing material is maintained almost the same as at the time of supplying the silver brazing material, and the same effects and functions as those in the above-described embodiment can be exhibited. .

[Brief description of drawings]

FIG. 1 is a perspective view showing a lead pin according to an embodiment of the present invention,
2 is a side view showing the lead pin body of FIG. 1, FIG. 3 is a perspective view showing the silver solder of FIG. 1, FIG. 4 is a cross-sectional view for explaining the joining process of the silver solder members, and FIG. Explanatory drawing showing the fillet height in a fluidity comparison test, FIGS. 6 to 8 are perspective views showing an example of the shape of a silver brazing member, FIG. 9 is a sectional view showing a conventional silver brazing method, and FIG. The figure is a side view showing an ideal state of molten silver solder, and FIGS. 11 and 12 are side views showing the state of silver solder flowing from the top surface of the top of the lead pin body. 1 ... Lead pin 3 ... Lead pin body 5 ... Silver brazing member 7 ... Jig 31 ... Top of lead pin body 31a ... Top bottom surface 31b ... Top top surface 33 ... Legs

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Nara 2-9-12 Kajimachi, Chiyoda-ku, Tokyo Inside the Tokoriki main store (72) Inventor Masanori Shiratori 1810 Nishicho, Takashiro-cho, Kawauchi-shi, Kagoshima Kyose La Co., Ltd. Kagoshima Kawauchi Plant (56) References JP-A-60-121063 (JP, A)

Claims (1)

[Claims] 1. A lead pin used for an external terminal of an IC ceramic package comprising a lead pin main body and a silver brazing member joined to the lead pin main body, wherein (a) the silver brazing member has a length of each side. Have the same cubic shape or have the same cylindrical shape with the same diameter and height, and (b) the silver brazing member is diffusion-bonded to one end face of the lead pin. And the lead pin.