JPH03116670A - Electric pin - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of a crack in solder and a ceramic substrate by sticking a high conductive body layer having sufficient thickness on the circumference of a core material except a pin part and also the tip part of a head part formed with a material having a low thermal expansion coefficient. CONSTITUTION:A material having a low thermal expansion coefficient is used as the core material 16 of a pin part 12 and the head part 14, and a high conductive body layer 18 having sufficient thickness is stack on the circumference of the core material 16 except the tip part 14a of a head part 14. When an electric pin 10 is soldered on a ceramic substrate 26, the thermal expansion coefficient of a whole head part 14 becomes considerably lower than that of copper itself since the head part 14 is formed with a cover layer 16 and a copper layer 18. This causes tensile stress generated during the cooling of solder 24 to be small to prevent the occurrence of cracks in solder and a ceramic substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to electrical pins, particularly for example in CPU (Central
The present invention relates to an electrical pin that is connected to a ceramic substrate (processing unit) via a brazing material and is suitable for electrically connecting a CPU and an external circuit element such as a memory.

[Conventional technology]

JP-A-57-18348 is used as a material for electrical pins that electrically connect between the CPU and external circuit elements such as memory.
As shown in the publication, Kov
ar) was used. The reason for this is that the coefficient of thermal expansion of Kovar is almost the same as that of a ceramic substrate, and when electrical pins made of Kovar are brazed onto a ceramic substrate, problems such as cracks (described later) may occur between the electrical pins and the ceramic substrate. This is because the occurrence of can be suppressed. FIG. 6 is a diagram showing an example of an electrical pin 100 using a base material 102 made of Kovar. In this example, the surface of the base material 102 is coated with a nickel plating layer 104 and a gold plating layer 1.
06 is formed.

[Problem to be solved]

However, due to Kovar's low conductivity, the voltage drop due to the resistance of the electrical pins using it is significant, and not only is it impossible to apply sufficient voltage to the CPU, but also the resistance of the electrical pins themselves in the power supply section Therefore, there was a problem in that it became a heating element.

In order to avoid the above-mentioned problem, it is conceivable to use a material with high conductivity, such as copper, as the material of the electric pin.

The problem in this case will be explained with reference to FIG. High conductivity materials such as copper generally have a coefficient of thermal expansion much larger than that of ceramics. For example, the coefficient of thermal expansion of mullite, a type of ceramic, is 3.0 x 10-'/
``C, whereas the coefficient of thermal expansion of copper is 17 x 1
0''/°C, which is about 6.7 times that of mullite. Therefore, when the electric pin 110 made of copper is brazed onto the ceramic substrate 122, the temperature of the solder metal is lowered during cooling to the chamber source after melting. A tensile stress 118 is generated due to the difference in thermal expansion coefficient between the copper 112 and the ceramic substrate 122, and the wax 12
0 and the ceramic substrate 122 are cracked.

Therefore, it is an object of the present invention to provide an electrical pin that has high conductivity (and does not cause cracks in the wax or ceramic substrate).

[Means to solve the problem]

The electrical pin of the present invention is an electrical pin having a pin portion formed to have substantially the same diameter over substantially the entire length, and a head portion formed at at least one end of the pin portion to have a diameter larger than the diameter, and particularly, A material with a low coefficient of thermal expansion is used as the core material of the head part and the head part, and a high conductive layer of sufficient thickness is applied around the core material except for the tip of the head part. .

〔Example〕

Embodiments of the electrical pin of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of the electrical pin 10 according to the present invention brazed to a substrate 26, FIG. 2 is a bottom view of the electrical pin 10 with the nickel plating layer and gold plating layer removed, and FIG.
5 through 5 are diagrams showing the manufacturing process of the electrical pin 10. As shown in FIG.

In FIG. 1, the electrical pin 10 of the present invention includes a core material 16 made of Kovar with a low coefficient of thermal expansion and a highly conductive layer 18 made of copper with high conductivity. The highly conductive layer 18 is formed over the entire length of the pin portion 12 excluding the tip or bottom surface 14a of the head portion 14 and the entire circumference of the head portion 14. In this embodiment, a thin nickel plating 20 and a thin gold plating 22 are applied all around the electrical pin 10 for corrosion resistance reasons.

In FIG. 2, a core material 16 made of Kovar is exposed at the tip 14a of the head portion 14 in a substantially concentric circle with the outer periphery of the head portion 14. It should be noted that according to the manufacturing method described below, the Kovar core material 16° at the tip 14a of the head portion 14 has a sufficiently larger area than the Kovar material of the pin portion 12.

Returning to FIG. 1 again, connect the electrical pin 10 to the ceramic substrate 2.
6, the molten wax 24 is soldered to the head portion 14.
It adheres to the bottom surface 14a and the outer periphery. As mentioned above, Kovar is exposed on the bottom surface 14a of the head portion 14 and is in contact with the wax 24 through the thin nickel plating layer and gold plating layer, and the thermal expansion coefficient of the entire head portion 14 is equal to the head portion I4. Because it is formed of a Kovar layer and a copper layer, its coefficient of thermal expansion is much lower than that of copper itself, so Low 24
The tensile stress generated during cooling is small, and the risk of cracking is significantly reduced. Further, most of the current flowing through the electric pin 10 is caused by the core material 1 made of Kovar having low conductivity.
Since the current flows through the copper layer I8, which has a higher conductivity than 6, the resistance is low, the voltage drop is small, a sufficient voltage can be applied to the CPU, and the electrical pin itself does not become a heating element.

Next, referring to FIGS. 3 to 5, the electric pin 1 of the present invention will be described.
The manufacturing method of 0 will be explained. That is, copper 32 is clad around the Kovar 30 in a conventional manner, and the formed rod 40 as shown in FIG. 3 is cut to a predetermined length. This cut rod 40 is held in a jig 50.5 as shown in FIG.
2 and process the header as well. For example, the end 40a of the rod 40 is struck with a hammer 54.

Since the hammer 54 is pre-formed with a concave shape (not shown) corresponding to the shape of the head, the head of the electric pin after being struck is formed into a predetermined shape as shown in FIG.

The formation of the head portions at both ends of the rod 40 may be performed in separate steps or may be performed simultaneously. Further, if necessary, only one end of the rod 40 may be formed with a head portion, and the other end may be simply formed into a hemispherical, conical, or pyramidal shape.

In order to improve the corrosion resistance of the electrical pin formed as described above, the electrical pin of the present invention is completed by applying thin nickel plating and thin gold plating.

Note that the method for forming the copper layer around Kovar is not limited to cladding, and other methods such as plating may be used, but cladding is preferable because it allows the formation of a highly conductive layer with a sufficient thickness. Also,
In the case of plating, it is difficult to use the long rod 40 shown in FIG. 3, and it must be done after cutting it to a predetermined length or processing the header.

In that case, a layer of high conductivity and high coefficient of thermal expansion is also formed at the tip of the head portion, which is not preferable for the above-mentioned purpose.

〔Effect of the invention〕

According to the electrical pin of the present invention, the material with a low coefficient of thermal expansion is substantially exposed at least in the central part of the tip of the head part, and the head part has a center part with a low coefficient of thermal expansion and an outer peripheral part with a high coefficient of thermal expansion. Since it is composed of two parts, the overall (average) coefficient of thermal expansion is low, and cracks in the solder and ceramic substrate can be effectively prevented during brazing while the solder is cooling.

In addition, since the electric pin of the present invention is covered with a sufficiently thick high conductive layer as a whole including the head, the current flowing through it is in the outer high conductive layer rather than in the low conductive core material. , the electrical pin has low resistance and the voltage drop is small (
For example, not only can sufficient voltage be applied to the CPU, but the electrical pins themselves do not become heat generating elements.

Additionally, the electrical pin of the present invention utilizes well-known technology and is therefore easy to manufacture.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the electrical pin of the present invention brazed to a ceramic substrate, Figure 2 is a bottom view of the electrical pin of the present invention with the nickel plating layer and gold plating layer removed, and Figures 3 to 3. FIG. 5 is a perspective view showing the manufacturing process of the electric pin of the present invention, and FIGS. 6 and 7 are cross-sectional views of the conventional electric pin and explanatory diagrams showing the problems of the electric pin. 10... Electrical pin 12... Pin part 14... Head part 1B... Core material 18... High conductor layer FIG, 1 Fl6.6 Fl6.2 Fl, G FIG, 3 FIG, 4 FIG, 5

Claims (1)

[Claims] (1) An electric pin having a pin portion formed to have substantially the same diameter over almost the entire length, and a head portion formed at at least one end of the pin portion to have a diameter larger than the diameter, the core of the pin portion and the head portion. An electrical pin, characterized in that the core material is made of a material with a low coefficient of thermal expansion, and a sufficiently thick high conductive layer is applied around the core material except for the tip of the head portion.