JP2002257849A - Coaxial probe for probe card - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coaxial probe, for a probe card, whose outside diameter can be made thin, as compared with that in the conventional cases. SOLUTION: The coaxial probe for the probe card is provided with a conductive needle 1, an external conductor 2 which is arranged and installed in a coaxial core shape on the outer circumferential side of the conductive needle 1, by keeping a gap from the conductive needle by exposing the tip part L of the conductive needle 1, fixation members 4A, 4B, 4C used also as spacers which comprise an electrical insulating property and which are arranged and installed between the external conductor 2 and the conductive needle 1 in at least positions in both end parts of the external conductor 2 and insulators 3, 3', which form a cylindrical shape partitioned by the conductive needle 1, the external conductor 2 and the fixation members 4A, 4B, 4C used also as the spacers and which are composed of air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial probe for a probe card provided in a probe card used for inspecting electrical characteristics of an IC chip (semiconductor device) formed on a semiconductor wafer.

[0002]

2. Description of the Related Art As is well known, in a semiconductor device manufacturing process, after a large number of IC chips (semiconductor devices) are formed on a semiconductor wafer, the electrical connection state and input / output characteristics of each IC chip are determined. An electrical measurement called a probe test is performed in order to check the IC chip, and the quality of these IC chips is determined in a state of the semiconductor wafer before each IC chip is divided. For this probe test, a probe card having a large number of probes arranged corresponding to the electrode pad arrangement of the IC chip formed on the semiconductor wafer is used. The probe card is electrically connected to the tester and transmits a test signal between the tester and the IC chip to be tested by bringing the corresponding probe into contact with each electrode pad of the IC chip to be tested. It is used for.

[0003] Recently, the operating speed of semiconductor devices has become increasingly faster, and accordingly, in a probe test, it is necessary to inspect an IC chip using a test signal of a high frequency of several hundred MHz. It has become. In a probe test using such a high-frequency signal, a coaxial probe for a probe card (hereinafter, referred to as “coaxial probe”) is used. Coaxial probe
It has a coaxial line structure like a coaxial cable, and has the advantages of lower transmission loss at high frequencies, less noise entering transmission signals, and stable characteristic impedance compared to two parallel lines. Have.

FIG. 5 is a longitudinal sectional view showing an example of a conventional coaxial probe for a probe card, and FIG. 6 is a sectional view taken along line CC of the coaxial probe for a probe card shown in FIG. As shown in FIGS. 5 and 6, this conventional coaxial probe has a conductive needle (center conductor) 11 for signal transmission, which is in contact with an electrode pad of an IC chip, and a tip of the conductive needle 11 exposed. An insulator 13 covers the outer periphery of the conductive needle 11 and an outer conductor 12 further covers the outer periphery of the insulator 13. The rear end of the conductive needle 11 is electrically connected to a conductive needle pad (conductive needle pogo seat) provided on the substrate of the probe card, and the conductive needle pad is electrically connected to the tester via the pogo pin. It is to be connected. Further, the rear end of the external conductor 12 is electrically connected to an external conductor pad (external conductor pogo seat) provided on the substrate of the probe card, and the external conductor pad is connected to the ground of the tester via the pogo pin. It is designed to be electrically connected.

[0005] The conductive needle 11 of the coaxial probe is made of a conductive metal having a spring property and abrasion resistance, for example, rhenium.
Made of tungsten alloy. The insulator 13 is made of an insulator having a small relative dielectric constant, for example, Teflon (trade name of “polytetrafluoroethylene”) in order to reduce transmission loss. The relative permittivity of Teflon is 2.1. The outer conductor 12 is made of a conductive metal, for example, a copper alloy or an aluminum alloy.
In such a conventional coaxial probe, the insulator 1
3 is made of Teflon and its characteristic impedance is 50
In the case of Ω, the outer diameter was about 1.1 mm.

By the way, as described above, the operation speed of a semiconductor device has been increased, and the degree of integration of the semiconductor device has been rapidly increased. For this reason, the distance between the electrode pads of the IC chip has been reduced (narrow pitch), and in order to cope with this, the outer diameter has been reduced so that many probe cards have a narrow pitch. There is a need for a coaxial probe that can be mounted by mounting.

[0007]

However, in the above-mentioned conventional coaxial probe, when obtaining a coaxial probe having a predetermined characteristic impedance, although the relative permittivity is small, the Teflon is several times larger than air. Since the insulator is formed by using such a method, the outer diameter of the coaxial probe could not be further reduced.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a coaxial probe for a probe card capable of reducing the outer diameter as compared with the related art. .

[0009]

In order to achieve the above-mentioned object, according to the present invention, a conductive needle and a distal end of the conductive needle are exposed to form a gap on the outer peripheral side of the conductive needle. Having an outer conductor arranged coaxially and having electrical insulation properties,
A spacer / fixing member disposed between the outer conductor and the conductive needle at least at both ends of the outer conductor, forming a space defined by the conductive needle, the outer conductor and the spacer / fixing member, A coaxial probe for a probe card, comprising: an insulator made of air.

According to a second aspect of the present invention, in the coaxial probe for a probe card according to the first aspect, the spacer / fixing member is made of polyimide or polytetrafluoroethylene.

According to the coaxial probe of the present invention, since the insulator made of air having a relative permittivity of 1.0 can be regarded as being small, the outer diameter can be reduced as compared with the prior art. it can. The reason will be described based on a formula for obtaining the characteristic impedance of a general coaxial line. FIG. 4 is a diagram showing a cross section of the coaxial line. In FIG.
1 denotes a center conductor, 52 denotes an outer conductor, and 53 denotes an insulator. The center conductor 51 corresponds to the conductive needle of the coaxial probe according to the present invention, the outer conductor 52 corresponds to the outer conductor of the coaxial probe according to the present invention, and the insulator 53 corresponds to the insulator of the coaxial probe according to the present invention. . The radius of the center conductor 51 is a (mm), and the outer radius of the insulator 53 is b.
(Mm), _assuming that the relative permittivity of the insulator 53 is εs, FIG.
The characteristic impedance Z ₀ (Ω) of the coaxial line shown in FIG.

Z ₀ = 138 · (ε _s ) ^1/2 · log (b / a) (1)

From equation (1), the characteristic impedance Z ₀ of the coaxial line is determined by the difference between the insulator 5 between the center conductor 51 and the outer conductor 52.
And the relative dielectric constant epsilon _s of 3, is determined by the distance from the center conductor 51 to the outer conductor 52. Therefore, as can be understood from Expression 1, when a coaxial line having a predetermined constant value, for example, a characteristic impedance Z _{0 of} 50Ω is formed using the center conductor 51 having the outer diameter 2a, the relative permittivity ε By providing an insulator 53 having a smaller _s, the outer diameter of the insulator 53 is smaller than that of the insulator 53 by a relative permittivity larger than that of the insulator 53.
b can be reduced, and thereby the outer diameter of the coaxial line can be reduced.

As understood from the above description, according to the coaxial probe according to the present invention having the coaxial line structure, since the relative dielectric constant can be regarded as 1.0, the insulator made of small air is provided. Thus, the outer diameter of the coaxial probe can be reduced as compared with the related art. As is well known, the substance having the smallest relative permittivity is vacuum (relative permittivity: 1.0000).
And the relative dielectric constant of air is 1.00059, which is a value that can be substantially regarded as 1.0.

In the coaxial probe according to the present invention, the spacer / fixing member having electrical insulation is disposed between the outer conductor and the conductive needle at least at each position of both ends of the outer conductor. This is for fixing the conductor and defining a cylindrical space made of air as an insulator between the conductive needle and the outer conductor in cooperation with the conductive needle and the outer conductor. In order to define a cylindrical space in cooperation with the conductive needle and the outer conductor, at least two spacer fixing members are required. An insulator made of air is provided between the conductive needle and the outer conductor in a portion other than a portion where the at least two spacer / fixing members are provided.
In a certain portion of the spacer / fixing member, the spacer / fixing member functions as an insulator for confining the propagation electromagnetic field.

Therefore, the spacer / fixing member is made of an insulator having a small relative dielectric constant, can accurately maintain a predetermined outer diameter of the insulator made of air, and has a member length of several meters.
A material having high mechanical strength (rigidity) is preferable so that the length is as short as possible. Further, it is preferable that the spacer / fixing member has good adhesiveness so that the conductive needle, the spacer / fixing member and the external conductor can be firmly integrated so as not to move with each other.

As a material of the spacer / fixing member having such functions and characteristics, polyimide (Polyimide) is most suitable. In addition, although the mechanical strength and adhesiveness are inferior to polyimide, polytetrafluoroethylene may be used as a material of the spacer / fixing member.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a coaxial probe for a probe card according to an embodiment of the present invention,
FIG. 2 is a sectional view taken along the line AA at the insulator position in FIG.
FIG. 2 is a sectional view taken along the line BB at the position of the spacer / fixing member in FIG. 1.

In this embodiment, the outer diameter D3 is 0.4
A coaxial probe having a characteristic impedance of 50Ω at 3 mm was manufactured. The coaxial probe according to the present embodiment is of a cantilever type (cantilever type) in which a conductive needle extends from obliquely above an IC chip and comes into contact with an electrode pad of the IC chip. This coaxial probe is shown in FIG.
As shown in FIG. 3, a conductive needle 1 and an outer conductor coaxially disposed with a gap between the conductive needle 1 and the distal end portion L of the conductive needle 1 being exposed. 2, which is electrically insulative and is disposed between the outer conductor 2 and the conductive needle 1 at both end positions and the center position in the longitudinal direction of the outer conductor 2 so that the outer conductor 2 is electrically connected to the conductive needle 1. Spacer / fixing member 4A, 4B, 4C to be fixed, conductive needle 1, outer conductor 2
And a cylindrical space defined between the conductive needle 1 and the outer conductor 2 by the spacer / fixing member 4A, 4B, 4C,
And insulators 3 and 3 'made of air.

The conductive needle 1 is made of a rhenium-tungsten alloy containing rhenium in an amount of 30% by mass, and has a surface plated with nickel in order to enhance its spring property (elasticity). The conductive needle 1 has a total length of 50 mm, an outer diameter D1 of the lead portion of 0.15 mm, and a length of the distal end portion L of about 2 mm.
The outer diameter of the tipmost portion that comes into contact with the electrode pads of the IC chip: about 25 μm.

The outer conductor 2 is made of a stainless steel tube whose front and inner surfaces are plated with nickel, and has high rigidity and spring properties. The outer conductor 2 has a total length of 28 mm, an inner diameter of 0.335 mm,
Outer diameter: 0.43 mm.

Also, the above-mentioned spacer / fixing member 4
A, 4B, and 4C use polyimide tubes. The spacer / fixing member 4 </ b> A provided between the outer conductor 2 and the conductive needle 1 at the position of the tip of the outer conductor 2 includes:
Total length LA is 3.0 to 3.5 mm, conductive needle 1 and outer conductor 2
The length LA 'of the portion sandwiched between is 2.5 to 3.0 m
m. The spacer / fixing member 4B disposed between the outer conductor 2 and the conductive needle 1 at the rear end position of the outer conductor 2 has a total length LB of 5.0 to 6.0 mm, and has a length LB of 5.0 to 6.0 mm. The length LB 'of the part sandwiched between is 2.5
〜3.0 mm. The spacer / fixing member 4C disposed between the outer conductor 2 and the conductive needle 1 at the center of the outer conductor 2 has a total length LC of 3.0 mm. That is, the three spacer / fixing members 4A, 4B, 4C
In this case, the lengths LA ', LB', and LC of the portions functioning as insulators for confining the propagation electromagnetic field are all reduced to about 3 mm.

An insulator 3 made of air forms a cylindrical space defined by the conductive needle 1, the external conductor 2, and the spacer / fixing member 4A, 4C, and also serves as the conductive needle 1, the external conductor 2, and the spacer. The outer diameter D2 of the insulator 3 'made of air in a cylindrical space defined by the members 4C and 4B is 0.335 mm.

To manufacture the coaxial probe constructed as described above, the spacer-fixing members 4A, 4B, and 4C made of a polyimide tube are closely fitted to the outer peripheral surface of the conductive needle 1 at predetermined positions. Process, and then
A step of applying an adhesive polyimide resin liquid to the outer peripheral surfaces of these spacer / fixing members 4A, 4B, 4C;
Thereafter, a step of inserting the conductive needle 1 to which the spacer / fixing members 4A, 4B, 4C are attached into the outer conductor 2 made of a nickel-plated stainless steel tube,
By holding the obtained product in a heating chamber in which the ambient temperature is set to about 120 ° C. for 60 to 120 minutes, the polyimide resin liquid is solidified, and the conductive needle 1, spacer / fixing members 4A, 4B, 4C and And integrating the external conductors 2 so that they do not move with each other.

As described above, when the outer diameter D3 is 0.43 mm, it has a characteristic impedance of 50Ω, and the outer diameter is reduced to about half of that of a conventional coaxial probe (outer diameter: about 1.1 mm). A coaxial probe was obtained. The coaxial probe according to the present embodiment provides 700 MHz
The probe test using the high-frequency test signal was successfully performed.

In the above-described coaxial probe according to the present embodiment, in order to reliably prevent contact between the conductive needle 1 and the outer conductor 2, the spacer / fixing member 4C is also provided at the center of the outer conductor 2 in the longitudinal direction. Is arranged. When the conductive needle 1 is as short as about 30 mm, the spacer / fixing member 4C provided at this central position is unnecessary. Regarding spacer / fixing members other than the spacer / fixing members 4A and 4B located at both end positions, depending on the length of the conductive needle 1,
What is necessary is just to arrange | position suitably. In addition, as the conductive needle 1, a gold-plated surface may be used instead of nickel plating to reduce electric resistance. Similarly,
As the external conductor 2, a metal plated on the surface may be used instead of the nickel plating. Furthermore, the outer conductor 2
In a probe card in which a large number of coaxial probes are densely mounted at a narrow pitch, an insulating material such as polyimide is formed on the outermost surface in order to prevent a short circuit even if adjacent external conductors come into contact with each other. Coated material may be used.

In the above-described embodiment, the coaxial probe of the wrench lever type has been described. However, the coaxial probe according to the present invention is a vertical contact type coaxial probe in which the conductive needle is in vertical contact with the electrode pad of the IC chip. Is also applicable.

Further, the present invention provides not only a coaxial probe but also, for example, a conductive needle (center conductor) 1 made of a copper wire and an outer conductor 2 made of a nickel-plated stainless steel tube to form a coaxial wire. It becomes possible to replace the enamel wire used for multilayer printed wiring by wires on the substrate of the probe card or the like with the coaxial line, and it is also applicable as a coaxial line in multilayer printed wiring by wires.

[0029]

As described above, according to the coaxial probe for a probe card according to the present invention, since the insulator made of air is provided, the outer diameter can be reduced as compared with the prior art. . As a result, a large number of probes can be mounted on the probe card at a narrow pitch, which can contribute to an improvement in efficiency of a probe test of a semiconductor device having a high degree of integration and a high operation speed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a coaxial probe for a probe card according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA at an insulator position in FIG.

FIG. 3 is a view showing a position B in FIG.
It is -B sectional drawing.

FIG. 4 is a diagram showing a cross section of a coaxial line.

FIG. 5 is a longitudinal sectional view showing an example of a conventional coaxial probe for a probe card.

FIG. 6 is a view showing a C of the coaxial probe for a probe card shown in FIG. 5;
It is -C sectional drawing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Conductive needle 2 ... Outer conductor 3, 3 '... Insulator 4A,
4B, 4C ... spacer and fixed member

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Genichi Wakata 2-5-1-13 Nishi-Nagasu-cho, Amagasaki-shi, Hyogo Japan Electronic Materials Co., Ltd. F-term (reference) 2G003 AA07 AB01 AG03 AH04 2G011 AA02 AA17 AA22 AB06 AC32 AE22 4M106 AA01 AA02 BA01 CA09 CA70 DD01 DD15

Claims (2)

[The claims] 1. A conductive needle, and an outer conductor which is exposed coaxially to the outer periphery of the conductive needle with a gap between the conductive needle and the distal end of the conductive needle, and has an electrically insulating property. A spacer / fixing member disposed between the outer conductor and the conductive needle at least at both ends of the outer conductor, and a space defined by the conductive needle, the outer conductor and the spacer / fixing member. A coaxial probe for a probe card, comprising: an insulator made of air. 2. The coaxial probe for a probe card according to claim 1, wherein said spacer / fixing member is made of polyimide or polytetrafluoroethylene.