KR20010025573A - high speed probe for test automation - Google Patents

Abstract

PURPOSE: A high speed probe for automatic testing is provided to test electronic devices and PCBs at fine pitches, speed up the testing process by mapping optimized impedance, and automatize the testing procedure. CONSTITUTION: In a high speed probe for automatic testing, an internal conductor open on both ends has a long hollow cylindrical body. A needle(15) can be inserted into the internal conductor with external pressure incurred by a spring. An external conductor(13) surrounds the internal conductor at a constant distance. Insulating rings hold the external conductor tight on both ends and insulate the external conductor(13) from the internal conductor. A coaxial cable(11) has a SMA connector(25) on one end and the other end is connected to the internal conductor(19).

Description

High speed probe for test automation

The present invention relates to a probe used in testing electronic components or PCB substrates, and more particularly, can be used for fine pitch, and can be used in high speed by optimally matching impedance, and at the same time, suitable for test automation. A high speed probe.

As semiconductor technology advances, terminal pitches of electronic components, including memories, are becoming increasingly finer. Before these electronic components are shipped, tests are conducted on whether the finished electronic components perform well. Only parts that pass these performance tests are shipped. On the other hand, as the terminal pitch of the electronic component becomes finer, the PCB substrate for mounting the electronic component is also miniaturized, and the PCB substrate is also shipped through a test process. 1 shows an example of a PCB substrate of this trend, and shows a PCB substrate for a memory board as an example.

Referring to FIG. 1, a slot 3 is formed at a lower portion thereof so that a memory substrate can be attached and detached, and a space 1 is formed to mount a memory. And the coupon part 5 is formed in the left and right both sides of the upper part.

When the substrate is tested, the slot 3 or the coupon unit 5 is tested with an inspection device to determine whether the impedance falls within a desired range. Conventionally, an oscilloscope is used as an inspection device, and the probe of the oscilloscope is contacted with the coupon part 5 to measure the impedance of the coupon part 5. However, such a test work is made manually, so there is a problem that the test takes a long time.

In general, the oscilloscope probe has a needle and ground separated from the signal transmission, and it is very inconvenient to use a fine pitch of 0.5 mm or less because of the size of the probe's end needle and the ground. Therefore, the test takes a long time, and because of this, it is impossible to test all PCB boards. However, the PCB receiving side hopes to test all PCB substrates, and the PCB supplying side does not satisfy the demands of the industry.

In addition, since the test operation is made manually, there is a problem in that the reliability is low because the difference is very different depending on the operator.

In order to solve the above problems, efforts have been made to automate tests. However, at present, no suitable probe for automation has been developed.

For automation, probes must be able to touch multiple test points at the same time, and multiple test points must be contacted at the same time, but automation probes that meet all of these requirements are still under development.

In addition, due to the structure of the oscilloscope probe, there is a problem in that accurate measurements cannot be made at high speed.

Impedance matching between the probe and the oscilloscope needs to be carried out without loss of the signal from the EUT to the probe to the oscilloscope. As a result, the industry has implemented impedance matching at the next stage of the coaxial cable so that signals can be transmitted without loss even at high speeds. However, even if impedance matching is performed as described above, due to the loop formed between the end of the probe and the object to be measured and the ground, impedance matching is not performed well at the front end of the coaxial probe, so the error due to this part has to be reduced. This has not been done. However, with the ever-increasing speed of an EUT, the need for more sophisticated impedance matching increases.

Accordingly, an object of the present invention is to provide a high speed probe for test automation that can be used for fine pitch, can be used at high speed by optimally matching impedance, and is suitable for automating a test.

1 is a view showing an example of a conventional PCB substrate.

Figure 2 is a perspective view of a high speed probe for test automation according to an embodiment of the present invention.

3 is a cross-sectional view of the probe of FIG.

4 is a perspective view of the needle of the probe of FIG.

5 is a state diagram used in the probe of FIG.

Figure 6 is a side view of the plate of Figure 5;

<Description of the code | symbol about the principal part of drawing>

11: coaxial cable 13: external conductor

15: needle 15a: spring

17: coupling ring 19: inner conductor

21: insulation ring 25: SMA connector

45: plate

In order to achieve the above object, the high speed probe for test automation according to the present invention includes: an inner conductor having a hollow cylinder having both sides open and elongated; A needle inserted into the inner conductor and supported by a spring to allow entry / exit into and out of one end surface of the inner conductor by an external pressure; An outer conductor having a cylindrical shape on both sides of the inner conductor at equal intervals around the inner conductor, and having open sides; An insulating ring fixed to the outer conductor at equal intervals from the inner conductor and positioned in both ends of the outer conductor for insulation between the inner conductor and the outer conductor; The connector is configured on one side, the other side is characterized by including a coaxial cable connected to the other side of the inner conductor.

Hereinafter, a configuration of a high speed probe for test automation according to the present invention will be described in detail with reference to the accompanying drawings. 2 is a perspective view of a high speed probe for test automation according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view of the probe of FIG.

Referring to FIG. 2, the high speed probe has an outer shape of a coaxial cable 11 having an SMA connector on one side and an elongated cylindrical + hollow outer conductor 13 connected to the other side of the coaxial cable 11. And a needle 15 inserted into the inner hollow of the outer conductor 13 and formed at one side to be in contact with the object to be inspected, and coupling the coaxial cable 11 and the outer conductor 13 to each other. It consists of a ring 17.

Referring to FIG. 3, a long hollow inner conductor 19 is formed in the inner hollow of the outer conductor 13, and the outer conductor 13 is disposed between both ends of the outer conductor 13 and the inner conductor 19. ) And an insulating ring 21 for insulating and supporting the inner conductor 19, and the needle 15 is inserted into the inner conductor 19.

The needle 15 is a configuration for transmitting a signal in contact with the object to be inspected, and FIG. 4 illustrates the needle 15 in detail. Referring to FIG. 4, the needle 15a is formed on one side, the spring 15b is formed on the center, and the other side 15c is another spring contact probe bent at a fine angle. As described above, since the needle 15 is another probe, in the present embodiment, the 'spring contact probe' and 'needle' are mixed for convenience.

The spring 15b is configured at the next end of the needle 15a for the purpose of securing the contact using one's own elastic force when one side of the needle 15a comes into contact with the inspected object. The spring 15b allows the needle 15a to elastically enter / exit into the inner conductor 19, so that when the needle 15 descends from the outside when it comes into contact with the inspected object, all of the needle 15a is not accurate. Accurate contact with the test point.

Since the end portion 15c of the spring contact probe 15 is bent at a predetermined angle, the spring contact probe 15 is inserted into the inner conductor 19 to be described later so that it does not easily come out. However, when the needle 15a of the spring contact probe is pulled from the outside, the spring contact probe 15 easily comes out of the inner conductor 19.

The spring contact probe 15 is inserted into the inner conductor 19 and the end portion 15c is in contact with the inner wall of the inner conductor 19. Thus, the signal transmitted through the needle 15 can be transmitted to the inner conductor 19.

Next, the inner conductor 19 is configured not only to perform the socket role of the needle 15, but also to cooperate with the outer conductor 13 to match the impedance, the outer diameter is about 0.3mm and the coaxial cable It is connected with the core wire 11a.

The inner conductor 19 is a detachable socket of the needle 15, and when one side of the needle 15 is damaged due to long use, only one side of the inner conductor 19 can be easily replaced. The needle 15 was made accessible by opening.

As described above, the other side 15c of the needle 15a is bent at a predetermined angle so that it is not easily separated from the inner conductor 19 due to the frictional force. However, when the needle 15 is forcibly pulled from the outside, it can be easily detached, and when the needle 15 is damaged, only the needle 15 can be replaced, thereby making it easy to maintain and maintain.

On the other hand, by the outer diameter of the inner conductor 19 and the inner diameter of the outer conductor 13, the characteristic impedance of the conductor portion (inner conductor 19 and outer conductor 13) that is the front end of the coaxial cable 11 is adjusted.

The outer conductor 13 serves to electrically shield the inner conductor 19 from the outside as well as to configure the characteristic impedance in cooperation with the inner conductor 19. The inner diameter is about 0.9 mm, and the outer diameter is It is about 1.2mm hollow conductor.

In order for the signal transmitted from the inspected object through the needle 15 to be transmitted to the inspection equipment without loss, the line must be impedance-matched with the input side. In the industry, it is desired to match a line with a characteristic impedance of 28 [Ω] or 50 [Ω]. Accordingly, in this embodiment, the outer diameter of the inner conductor 19 and the inner diameter of the outer conductor 13 are adjusted. The impedance was adjusted to 50 [Ω]. The characteristic impedance Z is calculated by the following equation.

On the other hand, this characteristic impedance should be applied to the track collectively. Therefore, in the present embodiment, the coaxial cable 11 was configured using a ready-made product having an outer diameter of about 1.2 mm and a characteristic impedance of 50 [Ω].

In Equation 1, the dielectric material is a dielectric material filled between the outer conductor 13 and the inner conductor 19, and its characteristic impedance is changed by the dielectric. In this embodiment, the dielectric is made air 23. That is, there is no dielectric between the outer conductor 13 and the inner conductor 19 and only the air 23 is filled, and the relative dielectric constant ε _r of the air 23 is 1.

Teflon is generally used as a dielectric for impedance matching in a probe. The Teflon has a relative dielectric constant of about 2.1. In this embodiment, when the Teflon is used as a dielectric, the thickness of the inner conductor 19 and the outer conductor 13 is increased to provide a probe that can be used at a fine pitch of 0.5 mm or less. Did not satisfy. Therefore, in the present embodiment, air 23 having a relative dielectric constant lower than that of the Teflon was used as the dielectric material to obtain a desired characteristic impedance value in the fine pitch.

In this embodiment, the characteristic impedance is matched in the frontmost conductor portions 13 and 19 that transmit signals by using air 23 as the dielectric and adjusting the inner and outer diameters of the coaxial cylindrical conductors 13 and 19. Since the coaxial cable 11 connected to the next stage is already optimized for characteristic impedance, the front end is impedance-matched, so that the probe is impedance-matched in all parts. Therefore, the probe can transmit a signal at high speed without loss, thereby generating an advantage that can be used for impedance measurement of a high speed PCB substrate and testing of a high speed IC. Test Results The probe according to the present example was usable at 800 MHz or higher.

Next, the insulating ring 21 is configured to insulate the outer conductor 13 and the inner conductor 19 and to support the inner conductor 19 at the center of the outer conductor 13. The insulating ring 21 is inserted into both ends of the outer conductor 13 to support the inner conductor 19. The use of the insulating ring 21 may affect the characteristic impedance of the conductor parts 13 and 19, but the influence of the insulating ring 21 may be negligible. However, if the influence of the insulating ring 21 is considered, the variation in the characteristic impedance due to the insertion of the insulating ring 21 may be offset by adjusting the inner diameter of the outer conductor 13 and the outer diameter of the inner conductor 19.

Next, the coaxial cable 11 is a configuration for transmitting the signal transmitted through the inner conductor 19 to the inspection equipment, the standard SMA connector 25 is configured on one side and the characteristic impedance is 50 [Ω]. . Therefore, when connecting the high speed probe to the inspection equipment, one side of the coaxial cable 11 may be inserted into the SMA connector configured on the inspection equipment side.

And the core wire (11a) located on the other side of the coaxial cable 11 is connected to the inner conductor 19 by soldering, and the coupling ring (17) is formed on the other outside of the coaxial cable (11) is coaxial with the outer conductor (13). Connect the cable (11). Therefore, the outer conductor 13 and the coaxial cable 11 is firmly connected.

5 is a diagram illustrating the use of the probe of FIG. 2 as described above. When the probe is used, a plurality of probes 30 are disposed in accordance with the shape of a coupon part as shown in FIG. 5, and then RF SMA connectors connected to the probes 30 are connected. The oscilloscope 43 may be connected to the switch 41 and the RF switch 41.

In the present embodiment, unlike the prior art, only the conductor (inner conductor 19) for signal transmission is configured in the probe 30, without configuring the ground. Therefore, the overall thickness of the probe 30 is minimized, and thus, the plurality of probes 30 can be arranged in accordance with the shape of the coupon unit as shown in FIG. 5. When arranging the probe 30, the probe connected to the ground of the PCB board should be separately placed. In addition, the plate 45 is provided so that the arrangement of the probe 30 is not scattered to form a hole in the plate 45 in the same shape as the coupon portion, and the terminal end of the outer conductor 13 of the probe 30 is inserted into the hole. Just do it.

5 shows an example where two test positions are used. In this case, the RF switch 41 is used halfway so that one point of oscilloscope 43 can measure several points at a time. The RF switch 41 sequentially switches a plurality of probes so that only one probe 30 may be connected to the oscilloscope 43.

6 shows a detailed view of the probe 30 inserted into the plate 45 from the side, and FIG. 6 shows only the lower part of the plate. Referring to FIG. 6, the end of the outer conductor 13 is inserted into the plate 45 to allow the needle 15 to protrude downward from the plate 45. In the test, as shown in FIG. 5, the plate 45 on which the probe 30 is set is lowered onto the substrate or component to be tested so that the needle 15 contacts the test point. The distance between the plate 45 and the test point is slightly narrower than the protruding length of the needle 15 so that the needle 15 can firmly contact the test point so that the needle 15 can firmly contact the test point by the elastic force of the spring. It is desirable to be able to.

As described above, in the probe 30 according to the present embodiment, the needle 15 is accessible by a spring. Therefore, even when all the needles 15 are not protruded to the exact same length, when the plate 45 is lowered onto the substrate in consideration of this point, the test can be performed by accurately contacting the substrate even if it is not completely flat.

As described above, the high speed probe for test automation according to the present invention is configured as a single probe by separating the signal transmission conductor and the ground, and allowing the needle 15 to enter and exit, and the conductor for signal transmission of the probe. The parts 13 and 19 were impedance-matched in the same manner as the characteristic impedance of the coaxial cable 11. Therefore, the probe is advantageous in that it can be used at high speed and easily used in automation equipment for testing a board or a component. The high speed probe for the present test automation is very useful for automating the testing of electronic components as well as fine pitch PCB substrates.

Claims (1)

An elongated hollow cylindrical inner conductor on both sides; A needle inserted into the inner conductor and supported by a spring to allow entry / exit into and out of one end surface of the inner conductor by an external pressure; An outer conductor having a cylindrical shape on both sides of the inner conductor at equal intervals around the inner conductor, and having open sides; An insulating ring fixed to the outer conductor at equal intervals from the inner conductor and positioned in both ends of the outer conductor for insulation between the inner conductor and the outer conductor; The connector is configured on one side, the other side is a high speed probe for test automation comprising a coaxial cable connected to the other side of the inner conductor.