JP2000021528A - Contact pin for IC socket - Google Patents

Abstract

(57) [Problem] To provide a contact pin for an IC socket that can be applied to an object to be inspected whose inspection terminals have a narrow pitch. SOLUTION: An arc-shaped leaf spring portion 5 is integrally formed between a base portion 2 and a tip probe 4 using a plate material.
In the contact pin for the C socket, the leaf spring portion 5
The thickness is 0.08 to 0.11 mm, and the width w is 0.8 to 0.1 mm.
The radius of curvature of the inner arc 5a of the leaf spring portion 5 is 3.0 to 5.0 mm, and the length of the outer arc 5b of the leaf spring portion 5 is 5.6 to 5. 9mm contact pin for IC socket.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact pin for an IC socket, and more particularly, to a contact pin for an IC socket which can effectively cope with a narrow pitch of an inspection terminal on an inspection object.

[0002]

2. Description of the Related Art Conventionally, IC sockets have been used for inspecting electrical characteristics such as bare chip ICs and LSIs or package type LSIs (hereinafter collectively referred to as "inspected objects").

[0003] Such an IC socket is, for example, provided on a surface of a circuit board on which a predetermined inspection circuit is wired.
A pin probe type in which contact pins provided with a spring mechanism are provided in a matrix, or a contact pin which is processed into an arc shape and has spring elasticity on the surface of a circuit board. And other types are known.

In actual use, an object to be inspected is placed on the tip probe of the contact pin in the IC socket, and the object to be inspected is further pressed downward to check the inspection terminal and the tip probe of the contact pin. Are brought into mechanical contact with each other to establish conduction. In such a case, the height of the inspection object and the height of the contact pins that stand in the forest are usually varied, but the variation is caused by pressing the inspection object downward, thereby causing the spring mechanism and the contact pin to have the above-described structure. It will be absorbed by spring elasticity.

In recent years, high-density mounting of inspection objects has been promoted for the purpose of realizing miniaturization, weight reduction, and multifunctionality of various electric and electronic devices. As a result, BGA and PGA types, in which ball electrodes are arranged in an array or a matrix on the lower surface, have rapidly become widespread, and lands have been arranged in an array on the lower surface. The LGA type is rapidly spreading.

Moreover, the pitch between the above-mentioned electrodes (lands) tends to be finer with the progress of high-density mounting. Specifically, at present, the pitch is reduced to about 0.5 mm. Therefore, recently, there has been a demand for the development of an IC socket that can cope with the inspection of the inspection object even if the pitch between the electrodes is such a narrow pitch.

[0007]

By the way, when developing an IC socket which can cope with an object to be inspected having a narrow pitch between electrodes, the pitch between contact pins arranged on the IC socket also becomes narrow. It is necessary to solve such problems.

First, the contact pins that stand adjacent to each other on the circuit board do not come into contact with each other during non-working, and do not touch each other even when deformed during working. That is, its shape must be designed. Then, while satisfying the above conditions, at the same time, even in the case of deformation during actual operation, an appropriate contact state is realized between the tip probe and the electrode of the inspection object, and the contact resistance between them is increased. Means that the spring elasticity must be designed to be an appropriate value.

Further, the inspection using an IC socket is a cumulative number of burn-in tests performed under a predetermined heating environment of, for example, 100 ° C. or more while a test object is placed thereon and a load is applied to a contact pin. In this process, thermal fatigue of the contact pin also occurs, and the elasticity of the spring does not deteriorate even in such a case. It is necessary to select a material having excellent durability.

As described above, when designing the contact pin corresponding to the narrow pitch between the electrodes, it is necessary to solve the above-mentioned restriction condition regarding the shape, to prevent the spring elasticity from deteriorating at the time of actual operation, and to improve the durability. It is necessary to consider problems such as selecting a suitable material.

The present invention relates to the pin probe type I
In order to solve the above-mentioned problem required for the contact pin in the IC socket which functions not by the C socket but by the spring elasticity of the contact pin itself, even if the pitch between the electrodes of the inspection object is narrow, An object of the present invention is to provide a contact pin for an IC socket that can sufficiently cope with the problem.

[0012]

In order to achieve the above object, the present invention provides an IC socket in which an arc-shaped leaf spring is integrally formed between a base and a tip probe using a plate. In the contact pin, the leaf spring portion has a thickness of 0.08 to 0.1 lmm and a width of 0.8 to 0.1 mm.
The radius of curvature of the inner circular arc of the leaf spring is 3.0 to 5.0 mm, and the length of the outer circular arc of the leaf spring is 5.6 to 5.9 mm. I characterized in that
A contact pin for a C socket is provided. In particular, a contact pin for an IC socket in which the plate is made of a beryllium copper alloy is provided.

[0013]

FIG. 1 shows an example A of a contact pin according to the present invention.

The contact pin A is formed by integrally molding a plate material, which will be described later, as a whole, and includes a base 2 disposed on a circuit board 1 and a ball electrode 3 of an inspection object indicated by a virtual line.
A leaf spring portion 5 having an arc shape is formed between the tip probe 4 and the tip probe 4 which comes into contact therewith.

The material of the plate material used for manufacturing the contact pin A is excellent in creep resistance in that the spring elasticity is unlikely to deteriorate even under the burn-in test and the durability can be ensured. Preferably, the material is In particular, a beryllium copper alloy is preferable. As described later, the contact pin A is required to have a small size and a considerably high dimensional accuracy. Therefore, industrially, the above-mentioned plate material is subjected to etching or the like. It is manufactured by press molding.

As a material of the plate material, a material whose spring elasticity is not so large may be used as a base material, and a material whose surface is coated with a metal material having a high elastic modulus to increase the overall spring elasticity may be used. Good.

Since the contact pin A has a circular arc shape as shown in FIG. 1 between the base 2 and the tip probe 4, the contact pin A is placed on the circuit board 1 as shown in FIG. Even if they are arranged, the pitch p between the tip probes can be reduced without contacting each other. In the case of this contact pin A, the pitch p is 0.8 mm.
The shape of the leaf spring portion 5 described later is designed as follows.

The leaf spring portion 5 has an inner circular arc 5a of the leaf spring portion 5.
The width w between the outer circular arc 5b of the plate spring portion and the outer circular arc 5b is a value described later, and the thickness is a thin plate material whose thickness in a direction perpendicular to the paper surface is a value t described later. The thinner the thickness t is, the smaller the pitch between the contact pins arranged in a direction perpendicular to the paper surface can be reduced. The spring elasticity cannot be obtained, and it is difficult to obtain a stable contact resistance, and at the same time, there is a problem that the material cost increases. As described above, in order to reduce the pitch between the contact pins A to 0.8 mm or less, a plate material having a thickness of 0.08 to 0.11 mm should be used. In particular, it is preferably 0.10 mm.

The width w of the leaf spring portion 5 is set to a value which is 0.8 to 1.0 times the thickness t. If the width w is smaller than 0.8 times the thickness t, the etching or press working applied to the production of this contact pin will cause
This is because it is difficult to obtain the required processing accuracy and difficulties arise in terms of stable supply, and if the thickness t is larger than 1.0 times the thickness, it becomes difficult in terms of securing stability as a spring. is there. For example, when the plate thickness t is 1 mm, it is preferable to form the plate spring portion 5 with the width set to 0.8 to 1.0 mm.

This leaf spring portion 5 has an arc shape,
The radius of curvature R of the inner arc 5a is 3.0 to 5.0 mm, and the length of the outer arc 5b, that is, the chord is 5.6 to 5.9 mm.

The above numerical values are based on the premise that the pitch between the contact pins is 0.8 mm or less, and further, to realize a stable contact resistance with the ball electrode of the test object. It is set in view of obtaining appropriate spring elasticity, preventing contact between adjacent contact pins, and reducing the overall height of the contact pins to make the IC socket as small as possible. .

That is, the shorter the length of the chord of the outer arc 5b of the leaf spring portion 5, the lower the height of the contact pin A is, which is advantageous in terms of miniaturization of the IC socket. Is too short, when the contact pin A is pressed downward by a required amount and deformed, the load on the leaf spring portion 5 increases, and the spring fatigue reaches a limit at an early stage, and the life of the contact pin A decreases. Will be invited. Also, if the length of this string is too long, IC
Difficulty arises in reducing the size of the socket. Therefore, the length of the outer arc 5b of the leaf spring portion 5 is 5.6 to 5.9 mm.
It is set to.

The smaller the radius of curvature R of the inner circular arc 5a of the leaf spring portion 5, the lower the height of the leaf spring portion 5 and the smaller the load when the leaf spring portion 5 is deformed. If the radius of curvature 5 is too small, the load is too small and the contact resistance of the test object with the ball electrode becomes unstable. Conversely, if the radius of curvature R is too large, the load when the leaf spring portion 5 is deformed increases, and the leaf spring portion becomes fatigued at an early stage, leading to a shortened life as a contact pin. For this reason, the radius of curvature R is set to 3.0 to 5.0 mm.

FIG. 3 shows another contact pin B of the present invention.

In the case of the contact pin B, a fillet is formed in a connecting portion 2a between the base 2 and the leaf spring portion 5 and a connecting portion 4a between the leaf spring portion 5 and the tip probe 4, so that this portion is formed. The width is widened in the radial direction of the arc to make the shape as a whole smooth.

When this contact pin B is deformed by being pressed by the ball electrode of the object to be inspected, it is connected to the connecting portion 2a between the leaf spring portion 5 and the base 2 and the connecting portion 4a between the leaf spring portion 5 and the tip probe. Since the applied stress is relieved, spring deformation can be caused only in the leaf spring portion 5, which is preferable in that it can withstand a higher load than the contact pin A.

[0027]

EXAMPLES Example 1 A beryllium copper alloy mill-hardened plate material having a Young's modulus of 14000 kg / mm ² (thickness t: 0.10 mm, width w: 0.09)
mm), a contact pin B having the shape shown in FIG. 3 was manufactured by etching. At this time, the curvature radius R of the inner arc 5a of the leaf spring portion 5 and the length (chord length) of the outer arc 5b were designed as shown in Table 1.

Each of the obtained contact pins A is incorporated into an IC socket, a load is applied to the tip probe, the leaf spring is released, the leaf spring is bent 10,000 times, and a temperature of 125 ° C. is further applied. For 1000 hours.

Next, an LGA type I is inserted into the IC socket.
The C package was set, and the contact resistance with the ball electrode was measured for 100 contact pins. In order to absorb the dimensional tolerance of each part and the variation of the assembly accuracy, the displacement of the leaf spring portion of the contact pin should be at least 0.2 m.
m is required, so at least 0.2 when measuring contact resistance
A displacement of mm is given to the leaf spring.

The results are shown in Table 1.

In Table 1, R0 indicates that when the number of pins whose contact resistance exceeds 100 mΩ is less than 3%, R1 indicates that the contact resistance is 1
When the number of pins exceeding 00 mΩ is 3% or more and the cause is insufficient load on the leaf spring portion, R2 has a contact resistance of 1
When the number of pins exceeding 00 mΩ is 3% or more, the cause is the deterioration of spring elasticity due to spring fatigue, and S indicates the case where the pins contact each other and short-circuit.

[0032]

[Table 1]

As is apparent from Table 1, the length of the chord at the leaf spring portion should be 5.6 to 5.9 mm. When the radius of curvature of the leaf spring portion is 4.0 to 5.0 mm, the condition as a spring is satisfied even if the length of the chord is 6.0 mm or more. However, in this case, the length of the contact pin is 0.4 mm longer than the minimum value of 5.6 mm, which is disadvantageous in terms of miniaturization of the IC socket.
For this reason, the radius of curvature at the leaf spring is 3.
It is understood that the length should be set to 0 to 5.0 mm and the length of the string should be set to 5.6 to 5.9 mm.

Example 2 A contact pin A shown in FIG. 1 was produced by etching a beryllium copper alloy mill hardened material having a Young's modulus of 14000 kg / cm ² and a plate thickness of 0.10 mm. The width w of the leaf spring portion 5 is 0.09 mm, and the radius of curvature of the inner circular arc 5a is 3.
The length of the outer arc 5b is 5.72 mm.

The spring constant in this state is 0.0145 kg / mm
Met.

Then, the pin is plated with Ni having a thickness of about 3 μm, and a Pd-2 layer having a thickness of about 0.3 μm is further formed thereon.
5% Ni plating was performed. The spring constant of the obtained pin was 0.0165 kg / mm.

As described above, the Young's modulus is about 19700 kg / m
By plating the Ni is m ^2, and the spring constant of the pin is larger 0.002 kg / mm. When the spring displacement is 0.4mm, the load is 6.6g and 5.8g.
Is equivalent to the difference.

The contact resistance with an IC package having an Au land was measured using the IC socket incorporating the pin under the same conditions as in Example 1 and then measured. The initial contact resistance was 30 mΩ or less. And, even after the treatment, the spring constant of the contact pin is approximately 0.0165 kg / mm.
Was held.

[0039]

As is apparent from the above description, the contact pin for an IC socket according to the present invention has a leaf spring portion.
By adopting the dimensions and shapes shown in the above, the spring has elasticity that can cope with the inspection of the inspection object in which the pitch between the inspection terminals is narrow, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a side view showing an example A of a contact pin of the present invention.

FIG. 2 is a side view showing a state where contact pins A of FIG. 1 are arranged.

FIG. 3 is a side view showing another contact pin example B of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit board 2 Base part 2a Connection part of base part 2 and leaf spring part 5 3 Ball electrode 4 Tip probe 4a Connection part of tip probe 4 and leaf spring part 5 5 Plate spring part 5a Inner arc of leaf spring part 5 5B leaf spring part Outer arc of 5 (string length)

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Masayuki Nakamura 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Yasuyuki Ozaki 116-402 F, Namikicho, Kuroiso City, Tochigi Prefecture (Reference) 2G003 AA07 AG01 AG12 2G011 AA01 AA15 AA16 AB01 AC14 AE03 AE22 4M106 AA04 BA01 CA60 DJ34 DJ40 5E024 CA01 CB04

Claims (3)

[Claims] 1. A contact pin for an IC socket, wherein an arc-shaped leaf spring is integrally formed between a base and a tip probe using a leaf material, wherein the leaf spring has a thickness of 0.08 to 0.1 lmm. The width is 0.8 to 1.0 times the thickness, the radius of curvature of the inner arc of the leaf spring is 3.0 to 5.0 mm, and the length of the outer arc of the leaf spring is A contact pin for an IC socket having a length of 5.6 to 5.9 mm. 2. The contact pin for an IC socket according to claim 1, wherein said plate member is made of a beryllium copper alloy. 3. The contact pin for an IC socket according to claim 1, wherein said plate material comprises a base material and a material covering the surface thereof, and said material has a higher elastic modulus than said base material.