JPH0799220A - Probe card, coaxial probe needle for probe card and their production - Google Patents

Abstract

PURPOSE:To reduce the reflection of transfer signals issued from a tester side by electrically connecting a terminal part as a central conductor of a coaxial probe needle member with a printed board circuit and further electrically connecting a terminal part of a circumferential conductor with an earth board. CONSTITUTION:A coaxial cable 31 is bent as a U shape and a far end part of the cable 31 is inserted into a hole 22b in an earth board 22. Further, an exposed probe needle member 33 is passed through a hole 21c of an electrode pattern 21b in a printed board 21 and it is projected by an appropriate length from the board 21. Then a conductor mesh 35 is soldered to an upper-surface conductive layer 22c of the board 22. On the other hand, a far end part 33e of the member 33 is soldered to the pattern 21b. Thus, impedance matching with a tester side can be accomplished, and furthermore the electrical reflection can be reduced and dielectric noise can be suppressed as well, resulting in an excellent testing property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe card used in a probe device for inspecting electrical characteristics of a semiconductor device or the like, a coaxial probe needle for a probe card, and a manufacturing method thereof. In particular, it relates to a vertical needle type high density probe card for multiple pins (hereinafter referred to as VTPC).

[0002]

2. Description of the Related Art A typical probe device is described in, for example, Japanese Patent Laid-Open No. 64-73632. The probe card of this device has a probe needle that obliquely contacts the pad to be tested. However, with the recent increase in the integration of semiconductor devices, the number of pads per chip has increased, and the pad size and the inter-pad spacing have also been reduced, making it impossible for diagonal probe type probe cards to deal with the problem. ing.

Therefore, in recent years, the VTPC disclosed in, for example, Japanese Examined Patent Publication No. 28288/1987 and No. 28862/1988, is used in place of the probe card of the oblique needle type.
Is being put to practical use. In this VTPC, the number of probe needles mounted is greatly increased compared to the above-mentioned oblique needle type,
That is, it is possible to reduce the pitch of the mounting needles and increase the number of mounting needles.

[0004]

[Problems to be Solved by the Invention] However, VTP
In C, since it is prioritized that the probe needles are made extremely thin and mounted at a fine pitch, the characteristic impedance and the shielding property of each probe needle are not taken into consideration. Therefore, due to impedance mismatch between the probe needle and the tester side, signal reflection may occur at the probe needle, or crosstalk (a type of noise) may occur between adjacent probe needles. As a result, an abnormal waveform (ringing) occurs in the transmission signal, which may adversely affect the probing test.

The coaxial cable has advantages such as less noise entering a transmission signal and stable characteristic impedance. Therefore, it is expected that various advantages will be brought about when the coaxial cable is used for wiring in the probe card. However, in the coaxial cable, although it is necessary to ground the peripheral conductor, it is difficult to take a space for connecting the peripheral conductor to the ground on the printed circuit board as the density increases.

In other words, the outer diameter of the coaxial cable probe needle is about 0.8 mm.
When the printed circuit board of C is used, each electrode pattern for soldering the board side end of the holder conductor of each probe needle is 1 mm to
It is necessary to arrange them at a narrow pitch of about 1.5 mm. It is space-consuming to provide an insulating distance between the narrow pitch electrode patterns on the same plane as the electrode patterns and to provide a ground conductive layer (ground) for soldering the ends of the conductors around each probe needle. Almost impossible.

Further, when the frequency of the test signal is in the high frequency region, when the signal passes through the transmission line having the characteristic impedance different from the characteristic impedance on the tester side, the signal is reflected and noise is generated. Therefore, it is necessary to match the characteristic impedance of the probe needle that serves as the signal transmission path with the characteristic impedance of the tester (impedance matching).

The object of the present invention is to reduce the reflection of the transmission signal from the tester side, and to reduce the induced noise such as crosstalk, and to obtain excellent testing characteristics. And to provide a manufacturing method thereof. Another object of the present invention is to provide a coaxial probe needle for VTPC having the above advantages and a method for manufacturing the same.

[0009]

A probe card according to the present invention is electrically connected to a tester and is in electrical contact with a circuit under test so that a test signal is transmitted between the tester and the circuit under test. A probe card used for transmission, comprising a board assembly having a printed board and a ground board insulated from each other, and a tip supported substantially by the board assembly, the tip being substantially perpendicular to a pad of a circuit under test. A coaxial probe needle assembly that is in contact with the coaxial probe needle assembly, wherein the coaxial probe needle assembly covers a central conductor including a tip portion that is brought into contact with a pad of the circuit under test and a portion other than the tip portion of the central conductor, A holder conductor that conducts with the conductor, a dielectric that surrounds the holder conductor, and a peripheral conductor that is coaxial with the holder conductor through the dielectric. When the sheath covering the periphery conductor,
And a terminal portion of the holder conductor is electrically connected to a circuit of the printed circuit board, and a terminal portion of the peripheral conductor is electrically connected to a circuit of the ground substrate.

A coaxial probe needle for a probe card according to the present invention is a coaxial probe needle used for transmitting a test signal between a tester and a circuit under test, and is substantially perpendicular to a pad of the circuit under test. Covering the center conductor including the tip part that is in contact with and the part of the center conductor excluding the tip part,
A holder conductor conducting to the central conductor, a dielectric surrounding the holder conductor, a peripheral conductor coaxial with the holder conductor via the dielectric, and a sheath covering the peripheral conductor, The terminal portion of the holder conductor is electrically connected to the circuit of the printed circuit board, and the terminal portion of the peripheral conductor is electrically connected to the circuit of the ground substrate.

In the method of manufacturing the coaxial probe needle for the probe card according to the present invention, the first coaxial cable having a characteristic impedance smaller than the characteristic impedance on the tester side is designed by using the mathematical expression for determining the characteristic impedance of the coaxial cable. Then, the dummy core wire is covered with a dielectric layer, this dielectric layer is covered with a conductive mesh, this conductive mesh is covered with a sheath, and a first coaxial cable having a characteristic impedance smaller than the characteristic impedance on the tester side is obtained. A central hole is formed in the first coaxial cable by forming the central conductor by pulling out the dummy core wire from the first coaxial cable, and a center conductor including a tip end portion that is brought into contact with the pad of the circuit under test is connected to the center. The portion of the conductor other than the tip is covered with a holder conductor to make the holder conductor conductive with the center conductor,
The holder conductor is inserted into the center hole so that the end portion of the holder conductor projects from the first coaxial cable to form a second coaxial cable, and the diameter of the holder conductor is smaller than the diameter of the dummy core wire. Is characterized by.

[0012]

[Function] Usually, a coaxial cable is made by a general technique,
A dummy core wire is extracted from this coaxial cable, and a separately formed probe needle member (holder conductor) is inserted into the extraction trace (hole) of this dummy core wire. At this time, the holder conductor for mounting has a smaller diameter than the dummy core wire. As it can be inserted smoothly into the extraction mark. Moreover, since this probe needle member is inserted afterwards, it can be separately and easily molded into a form having a required outer diameter dimension in consideration of rigidity and conductor resistance and a buckling tip side portion having a one-step smaller diameter. For this reason, the manufacture of the coaxial probe needle having the required probe needle member at the center becomes very simple, and the troublesome post-processing is unnecessary.

Further, when a coaxial cable is made using a dummy core wire having a slightly larger diameter so that the probe needle member for mounting is used as a reference, it can be easily replaced, based on the calculation formula of the characteristic impedance of the high frequency coaxial cable, Make a coaxial cable smaller than the desired characteristic impedance by selecting the material and thickness of the dielectric, and replace the dummy core wire of this coaxial cable with the probe needle member for mounting, so that it matches the tester side as much as possible. A coaxial probe needle having a desired characteristic impedance can be easily obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, a wafer mounting table 1 is provided as a main stage in the approximate center of a base (not shown) of the automatic probe apparatus. The wafer mounting table 1 is provided on an XYZ-θ moving table (not shown) so that it can be moved linearly along the X-axis, Y-axis, and Z-axis and can be rotated around the θ-axis. Has become. The wafer mounting table 1 has a vacuum chuck mechanism (not shown), and one semiconductor wafer W is suction-held on the mounting table 1.

A VTPC 2 faces the upper surface of the wafer mounting table 1. VTPC2 is a card holder (not shown)
The card holder is fixedly supported by a head plate (not shown) and an insert ring (not shown). Further, a contact ring 3 and a test head 4 are provided above. Contact ring 3
Includes a performance board (not shown) and an interface block (not shown). The performance board is a board for allocating pin electronics of the tester and for wiring such as power supply ground.
The interface block has cables and pogo pins for connecting the VTPC 2 and the performance board.

The contact ring 3 is electrically connected to the test head 4 by a measuring interface including a cable and pogo pins. The contact ring 3 and the test head 4 are electrically connected to the external tester 5 by cables and pogo pins.

Next, referring to FIG. 1 and FIG.
C2 will be described. VTPC2 is a printed circuit board 2
1, ground substrate 22, fixed blocks 23, 24, 25,
26, a distribution plate (fixed plate) 27, guide plates 28 and 29, and a large number of coaxial probe needles 31 are assembled. Coaxial probe needle 3 on printed circuit board 21
A large number of circuits corresponding to 1 are formed. An opening 2 for passing a coaxial probe needle 31 is provided in the center of the printed board 21.
1a is formed. A large number of electrode patterns 21b are connected to the circuits on the front and back surfaces of the printed board 21. A through hole 21c for inserting the probe needle member 33 is formed in each electrode pattern 21b. The diameter of the through hole 21c is 250 to 500 μm. The electrode pattern 21b is 1
They are arranged at a narrow pitch of about mm to 1.5 mm.

The ground board 22 is placed on the printed board 21 and fastened together by screws 22e. The ground board 22 is insulated from the printed board 21.
A thin copper foil 22c is attached to the upper surface of the ground substrate 22. The coaxial probe needle 3 is provided in the center of the earth substrate 22.
An opening 22a for passing 1 is formed. Through hole 2
2b is formed on the ground board 22 so as to correspond to the through hole 21c of the printed board 21.

Ring-shaped fixed blocks 23, 24, 2
5, 26 are concentrically fastened to the lower side of the printed circuit board 21 one after another by positioning pins, fastening screws (not shown) and the like. The upper fixed block 24 holds the distribution plate 27 at the center of the ring. The lower fixed block 26 holds two guide plates 28 and 29 at the center of the ring. Distribution plate 2
7 and the guide plates 28 and 29 are provided in parallel with each other. The distribution plate 27 and the guide plates 28 and 29 are made of insulating resin. A large number of through holes 27a, 28a, 29a are formed in each plate 27, 28, 29 in the same arrangement pattern.

The ring central regions of the upper fixing blocks 23 and 24 are filled with an epoxy resin adhesive 32.
The coaxial probe needle 31 is fixed to the distribution plate 27 and the fixed blocks 23 and 24 with an adhesive 32. Since the bending portion 33a of the coaxial probe needle 31 is not fixed to the guide plates 28 and 29, when the tip 33b is strongly pressed against the pad P, the bending portion 33a is elastically deformed.

A large number of coaxial probe needles 31 of the present invention as probe needles are mounted on such a probe card 2. The center conductor 33g of the probe needle member 33 is made of gold and copper (Au-Cu) in order to reduce contact resistance and durability.
Made of alloy. The bending portion 33a is about 10 mm,
The needle tip (tip) 33b is approximately 250 from the lower guide plate 29.
It is projected downward by about μm.

The dielectric (internal insulator) 34 has a thickness of 0.
It is made of FEP with an outer diameter of about 158 mm and about 0.57 mm. The peripheral conductor (shield or the like) 35 is made of a tin-plated annealed copper braided shield wire. The sheath (external insulating coating) 36 is
It is made of polyester resin with a thickness of 0.025 mm and a standard outer diameter of 0.8 mm. By combining these materials and sizes, the characteristic impedance of the coaxial probe needle 31 (about 50 Ω) becomes compatible with the characteristic impedance of the tester 5.

A case where a chip on the semiconductor wafer W is subjected to a probing test will be described. A wafer W is mounted on the wafer mounting table 1, and the wafer mounting table 1 is moved to XYZ-
The probe tip 33b of each probe needle is brought into contact with the pad P of each chip by moving in the θ direction. At this time, overdrive is applied to ensure the mutual contact state between the needle tip 33b and the pad P. A test signal is transmitted from the external tester 5 to each probe needle 31 via the contact ring 3 and the test head 4.

Next, a method of manufacturing the probe card will be described with reference to FIGS. First, as shown in FIG. 1, the guide plates 28 and 29, the probe needle member 33, and the like are assembled in a shape below the fixed block 23.
The probe needle member 33 is a central conductor 33 having an average diameter of 70 μm.
The outer side of g is covered with a holder tube 33h having an outer diameter of 200 μm. The bending portion 33a has a length of about 10 m.
m, and the tip 33b is formed to have a diameter of about 15 μm. The distribution plate 27 and the two guide plates 28, 29 are set apart from each other and in parallel. Each plate 27, 28, 29
Are components of the probe card 2. Each plate 27, 2
A large number of through holes 27a, 28a, 29a are formed in 8 and 29, and the central axes of these through holes 27a, 28a, 29a are aligned. Tip portion 33 of probe needle member
a is successively inserted into the through holes 27a, 28a, 29a. The tip portion 33a is projected from the guide plate 29 by a predetermined length. A short circuit test is performed for each probe needle member 33. The through hole 27a is filled with an adhesive, and the probe needle member 33 is temporarily fixed to the distribution plate 27 (step S6).

Next, a method of manufacturing the first coaxial cable 31A will be described with reference to FIGS. 5 to 7 and steps S7 to S12 of FIG. A release agent is applied to the dummy core wire 33A (step S7). This dummy core wire 33A is melted F
EP (fluorinated ethylene propylene
ropylene) and cool. As a result, the dummy core wire 33A is covered with the dielectric 34 (step S
8). The dielectric 34 has an average thickness of 0.158 mm and an average outer diameter of 0.57 mm.

Further, the dielectric 34 is covered with a conductor mesh (surrounding conductor) 35 (step S9). Conductor mesh 35
Is a braided body in which tin-plated 0.05 mm diameter copper wire is woven.

Further, the conductor mesh 35 has an average thickness of 0.
When it is covered with the 025 mm sheath 36, it becomes the first coaxial cable 31A as an intermediate product as shown in FIG. 5 (step S10). The sheath 36 is made of a polyester film (trademark Millen mil-ene). The sheath 36 is bonded to the conductor mesh 35 with a vinyl chloride adhesive. The average outer diameter of the first coaxial cable 31A is 0.8 mm.

The sheath 36 of the first coaxial cable 31A is partially removed to expose the end of the dummy core wire 33A (step S11). Next, connect the dummy core wire 33A to the cable 31.
When pulled out from A, a cable 31A having a central hole 31c as shown in FIG. 6 is obtained (step S12). Central hole 31c
Has an average diameter of 254 μm.

The large diameter portion of the probe needle member 33 described above projects upward from the distribution plate 27. The large diameter portion of the probe needle member 33 is inserted into the center hole 31c of the cable 31A (step S13). As a result, as shown in FIG. 6, the second coaxial cable 31 is obtained as a finished product.

Next, a method of treating the end of the coaxial cable 31 will be described. The coaxial cable 3 is arranged so that the coaxial cable 31 protrudes above the distribution plate 27 by a length of 50 to 70 mm.
Trim the end side of 1. The sheath 36 is partially removed to expose the conductor mesh 35 at the end of the cable. Further, the conductor mesh 35 and the dielectric 34 are partially removed to expose the probe needle member 33 at the end of the cable. The exposed length of the probe needle member 33 is 10 to 20 mm. The exposed length of the conductor mesh 35 is 10 to 20 mm.

Bend the coaxial cable 31 to make a U-turn,
The end of the cable is inserted into the hole 22b of the ground board 22. Further, the exposed probe needle member 33 is inserted into the hole 21c of the electrode pattern 21b of the printed board 21, and the probe needle member 33 is projected from the printed board 21 by an appropriate length. Then, the conductor mesh 35 is soldered to the upper conductive layer 22c of the ground substrate 22 (step S1).
4). On the other hand, the terminal portion 33e of the probe needle member is soldered to the electrode pattern 21b (step S15).

As shown in FIG. 7, the side of the conductor mesh 35 is the ground side. The probe needle member 33 side is the signal line side. Here, in order to prevent the reflection of the transmission signal at each probe needle, the characteristic impedance Z on the probe needle side is
₂ may be made as equal as possible to the characteristic impedance Z on the tester side (step 16).

In impedance matching,
Measure the impedance Z ₂ and measure the impedance ratio Z ₂ /
Z is in the range of 0.9 to 1.1 (0.9 <Z ₂ / Z
If it is <1.1), it can be said that a practically good effect can be obtained.
Adopt this. The value of the impedance ratio Z ₂ / Z is 0.
When it is 9 or less or 1.1 or more and is out of the above-mentioned proper range, the first coaxial cable 31A is replaced with another one.

Next, impedance matching will be described using the following equations 1, 2, and 3. Formula 1 is a formula for obtaining the characteristic impedance Zo (Ω) of a general high-frequency coaxial cable. The dielectric constant, the material, the thickness, and the like of the dielectric 34 are selected based on Equation 1 to create the first coaxial cable 31A having a smaller characteristic impedance (50Ω) than the desired characteristic impedance (about 37Ω).

[0035]

[Equation 1]

[0036]

[Equation 2]

[0037]

[Equation 3]

However, in the equation 1, d is the outer diameter of the central conductor [mm] K ₁ : the effective diameter coefficient of the central conductor D: the outer diameter of the dielectric [mm] Er: the dielectric constant of the dielectric dw: the diameter of the braided shield wire .

The dummy core wire 33A is made of tin-plated annealed copper and has an outer diameter d ₂ = 0.254 mm and a center conductor effective diameter coefficient K ₁ = 1. The dielectric (internal insulator) 34 is made of FEP with a dielectric constant Er = 2.1 and has an inner diameter of 0.254 m.
m, the thickness is 0.158 mm, and the outer diameter D is 0.57 mm.

The outer conductor (shield, etc.) 35 is composed of 35 braided shielded wires made of tin-plated annealed copper. The wire diameter dw is 0.05 mm, and this is tin-plated with a density of 90% or more, and the average outer diameter is 0.67 mm.

The sheath (external insulating coating) 36 has a thickness of 0.
Finishing of 025mm Standard outer diameter 0.72mm Made of Millen material. With this, the characteristic impedance Z ₁ of the first coaxial cable 31A is obtained by the mathematical expression 2.

As shown in FIG. 6, the dummy core wire 33A is extracted from the first coaxial cable 31A manufactured in such a state as to have an impedance of about 37Ω, and the hole 31c of the extraction trace has a diameter d ₁ slightly smaller than this. As for the characteristic impedance Z ₂ of the second coaxial probe needle 31 obtained by inserting the probe needle member 33 of = 200 μm, the effective permittivity Ee of the dielectric 34 is first obtained as in Expression 3. By substituting this into Equation 2, the characteristic impedance Z ₂ is obtained.

As described above, the coaxial probe needle 31 having the characteristic impedance Z ₂ matching the characteristic impedance Z on the tester side is obtained. Such a coaxial probe needle 3
If a large number of 1's are mounted on the probe card 2 and used, reflection of a transmission signal is reduced. Further, even with the probe needle members 33 arranged at a fine pitch, crosstalk is suppressed,
The occurrence of abnormal ringing can be prevented and excellent testing characteristics can be obtained.

The probe needle member 33 is a dummy core wire 3
Since the diameter is smaller than 3A, it can be smoothly inserted into the center hole 31c. Moreover, since the probe needle member 33 can be manufactured separately from the coaxial cable 31A, the needle tip portion 3
3b can be easily polished. Therefore, the assembling process is relatively easy, and the troublesome post-processing is unnecessary.

First, the target characteristic impedance (5
Create a coaxial cable 31A with a characteristic impedance (37Ω) smaller than 0Ω, and then dummy wire 33A.
Is replaced with the probe needle member 33, the coaxial probe needle 31 having the target characteristic impedance (50Ω) can be easily obtained.

According to the above embodiment, the coaxial probe needle 31
Since the end of the above is processed at the ground substrate 22 and the space on the upper surface of the printed substrate 21 can be effectively utilized, a VTPC having a large number of pins can be easily manufactured.

Further, according to the above-mentioned embodiment, it is possible to reduce the reflection of the signal on the transmission line, and the effect of suppressing the induced noise such as crosstalk is great, so that excellent testing characteristics can be obtained.

[0048]

Since the coaxial needle for a probe card of the present invention is constructed as described above, impedance matching with the tester side can be achieved to reduce electric reflection, and the effect of suppressing induction noise such as crosstalk is large. It has excellent testing characteristics and is optimal as a mounting needle for a vertical needle type ultra-high density probe card. According to the method of manufacturing a coaxial needle for a probe card of the present invention, an excellent coaxial needle for a probe card as described above can be manufactured very easily.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a probe card according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a part of the probe card in an enlarged manner.

FIG. 3 is a process drawing showing the method of manufacturing the probe card.

FIG. 4 is a process drawing (continuation) showing the method for manufacturing the probe card.

FIG. 5 is a cross-sectional view of a coaxial cable (intermediate product) including a dummy core wire.

FIG. 6 is a cross-sectional view of the coaxial cable excluding the dummy core wire.

FIG. 7 is a cross-sectional view of a coaxial cable (completed product) including a center conductor.

FIG. 8 is a circuit diagram showing a simplified signal transmission circuit of a probe card for explaining impedance matching.

[Explanation of symbols]

2 ... Probe card, 21 ... Printed circuit board, 21a
... Substrate central opening, 27, 32 ... Needle adhesive fixing part (27 ... Fixing plate, 30 ... Adhesive), 31 ... Second coaxial cable,
31A ... 1st coaxial cable, 33 ... Probe needle member, 33a ... Bending part, 33b ... Tip (needle tip), 3
3e ... Proximal end (terminal), 33g ... Central conductor, 33h ... Holder conductor, 34 ... Dielectric material, 35 ... Surrounding conductor, 36 ...
Sheath, W ... DUT (semiconductor wafer).

Front page continuation (72) Inventor Nobuyuki Negishi 2-25-25 Miyasaka, Setagaya-ku, Tokyo Junko Co., Ltd.

Claims (9)

[Claims] 1. A tester electrically connected to the tester,
A probe card used for transmitting a test signal between a tester and a circuit under test by electrically contacting the circuit under test, the board assembly having a printed circuit board and a grounding board insulated from each other, A coaxial probe needle assembly supported by the substrate assembly, the tip of which is in contact with the pad of the circuit under test substantially perpendicularly thereto, the coaxial probe needle assembly being in contact with the pad of the circuit under test. And a holder conductor that covers the portion other than the tip of the center conductor and that is electrically connected to the center conductor, a dielectric that surrounds the holder conductor, and the holder conductor through the dielectric. The holder conductor has a peripheral conductor provided coaxially and a sheath covering the peripheral conductor, and the terminal portion of the holder conductor is electrically connected to the circuit of the printed circuit board. To be connected, a probe card terminal portion of the peripheral conductor, characterized in that it is electrically connected to the circuit ground board. 2. The probe card according to claim 1, wherein the dielectric is made of fluorinated ethylene propylene. 3. The probe card according to claim 1, wherein the sheath is made of polyester resin. 4. The probe card according to claim 1, wherein an average outer diameter of the holder conductor is smaller than an average inner diameter of the dielectric, and a gap is formed between the holder conductor and the dielectric. 5. The holder conductor has an average outer diameter of 200 ± 20.
The probe card according to claim 5, wherein the probe card has a thickness of μm. 6. The probe card according to claim 5, wherein the average inner diameter of the dielectric is 254 ± 20 μm. 7. The grounding board is superposed on the printed circuit board, the through holes of the grounding board are formed at positions corresponding to the through holes of the printed circuit board, and the holder conductors are inserted into these through holes. The probe card according to claim 1, wherein the end portion projects from the printed circuit board. 8. A coaxial probe needle used to transmit a test signal between a tester and a circuit under test, the coaxial conductor needle including a tip portion which is in contact with a pad of the circuit under test substantially perpendicularly thereto. A holder conductor that covers a portion of the center conductor other than the tip portion and is electrically connected to the center conductor; a dielectric that surrounds the holder conductor; and a peripheral conductor that is provided coaxially with the holder conductor through the dielectric. A sheath covering the peripheral conductor, the terminal portion of the holder conductor being electrically connected to the circuit of the printed circuit board, and the terminal portion of the peripheral conductor being electrically connected to the circuit of the ground circuit board. A coaxial probe needle. 9. The method of manufacturing a coaxial probe needle uses a mathematical expression for determining a characteristic impedance of a coaxial cable, designs a first coaxial cable having a characteristic impedance smaller than a characteristic impedance on a tester side, and sets a dummy core wire. A dielectric layer is coated, this dielectric layer is coated with a conductive mesh, and this conductive mesh is coated with a sheath to form a first coaxial cable having a characteristic impedance smaller than the characteristic impedance on the tester side. By pulling out the dummy core wire from the first coaxial cable, a central hole is formed in the first coaxial cable, and a central conductor including a distal end portion that is brought into contact with the pad of the circuit under test is connected to the central conductor. The other part is covered with a holder conductor to make the holder conductor conductive with the center conductor, and the end of the holder conductor is the first coaxial cable. Insert the holder conductor to said central hole so as to al projects, the second coaxial cable is formed, the manufacturing method of the coaxial probe diameter of the holder conductor, characterized in that less than a diameter of the dummy wire.