PROBE SYSTEM FOR TESTING OF DEVICES UNDER TEST INTEGRATED ON A SEMICONDUCTOR WAFER, AND PROBE CARD, PROBE HEAD, AND GUIDING PLATE STRUCTURE THEREIN

A probe system and a probe card, a probe head and a guide plate structure thereof are described herein. The probe head includes a plurality of probes and guide plates. Each probe includes a first end, a second end, and a probe body. The first end is configured to abut a contact pad of the device under test. The second end is configured to abut a contact pad of a board of the probe system. The probe body extends between the first end and the second end according to a longitudinal development axis. The guide plate includes a pair of first guide holes for a pair of probes to pass through, and the pair of first guide holes are configured to slidably accommodate the pair of probes. The material between the pair of first guide holes in the guide plate has a relative dielectric constant not greater than 6, so as to reduce the return loss between the probe head and the device under test.

BACKGROUND OF THE INVENTION

The present invention relates to a probe head and a guide plate structure in the probe head. More specifically, the present invention relates to a probe head and a guide plate structure thereof which reduce the return loss between a probe card comprising the probe head and a device under test.

As a tool for testing the electrical properties of a semiconductor wafer or a packaged device, a probe card may generally comprise at least a probe head, a space transformer and a circuit board. The probe head may comprise a plurality of probes, and each of the plurality of probes may contact with a device under test (DUT) integrated in a semiconductor wafer to test the electrical performance of the device under test.

In recent years, the demand for high-frequency/high-speed testing of electronic devices under test is increasing day by day, and with the increase of data transmission rate during testing (e.g., from 50 to 60 Gigabits per second (Gbps) to more than 100 Gbps), the influence of impedance matching between the probe head as a whole and the device under test on high-speed signal transmission has become more significant. When the impedance of the test path (that is, the signal transmission path) is not matched, the influence of return loss will become significant.

However, since the probe head not only comprises electronic components but also comprises non-electronic components (e.g., probes and guide plates) together, mechanical characteristics of these components must be taken into account in the design of impedance matching thereof. Because it involves different types of components and the influence of the mechanical structure needs to be considered in the electrical design, such design is more difficult than the space transformer and the wiring substrate (e.g. printed circuit board, PCB) disposed thereon. Accordingly, an urgent need exists in the art to improve the degree of impedance matching between the probe head as a whole and the device under test.

SUMMARY OF THE INVENTION

In order to at least solve the above technical problems, the present invention provides a guide plate structure of a probe head of a probe system for testing a device under test integrated in a semiconductor wafer. The guide plate structure may comprise a first guide plate. The first guide plate may comprise a pair of first guide holes for a pair of probes of the probe head to pass through and extend according to a longitudinal development axis, and the pair of first guide holes may be configured to slidably accommodate the pair of probes. A first material between the pair of first guide holes in the first guide plate may have a relative dielectric constant not greater than 6. The first material is configured to provide a compensating impedance between the pair of first guide holes, and the compensating impedance is used to improve the impedance matching when probing the device under test with the pair of probes, so as to reduce a return loss between the probe head and a device under test.

In order to at least solve the above technical problems, the present invention further provides a probe head of a probe system for testing a device under test integrated in a semiconductor wafer. The probe head may comprise a plurality of probes, and each of the plurality of probes may comprise a first end, a second end, and a probe body. The first end ends at a contact tip and is configured to abut a contact pad of the device under test. The second end ends in a contact bottom and is configured to abut a contact pad of a board of the probe system. The probe body extends between the first end and the second end according to a longitudinal development axis. The probe head may further comprise a first guide plate, the first guide plate may comprise a pair of first guide holes for a pair of probes among the plurality of probes to pass through and extend according to the longitudinal development axis, and the pair of first guide holes are configured to slidably accommodate the pair of probes. A first material between the pair of first guide holes in the first guide plate may have a relative dielectric constant not greater than 6, so as to reduce a return loss between the probe head and the device under test.

In order to at least solve the above technical problems, the present invention further provides a probe card of a probe system for testing a device under test integrated in a semiconductor wafer. The probe card may comprise a circuit board, a space transformer arranged on the circuit board, and a probe head as described above. The probe head may be arranged on the other side of the space transformer opposite to the circuit board, and a second end of each of the plurality of probes in the probe head is configured to be electrically connected with the space transformer.

In order to at least solve the above technical problems, the present invention further provides a probe system for testing a device under test integrated in a semiconductor wafer. The probe system may include a chuck, a testing apparatus, and a probe card as described above. The chuck may be used for supporting the semiconductor wafer. The testing apparatus may be electrically connected with the device under test (i.e., the object to be tested) and used for establishing an electrical test program. The probe card may be arranged in the probe system.

According to the above descriptions, the probe head and the guide plate structure thereof provided by the present invention adopt the material with low relative dielectric constant as the guide plate material between a pair of probes corresponding to a group of differential signals, thus effectively reducing the impedance fluctuation caused by the guide plate between the pair of probes, thereby further reducing the return loss between the probe head as a whole and the device under test. That is, the impedance matching between the probe head (even the probe card to which the probe head belongs) as a whole and the device under test is improved. The more groups of probe pairs for differential signals are the abovementioned mechanism provided by the present invention applied to, the higher improvement effect can be obtained.

The above content provides a basic description of the present invention, including the technical problems solved by the present invention, the technical means adopted by the present invention and the technical effects achieved by the present invention, and various embodiments of the present invention will be further exemplified in the following description.

What shown inFIG.1toFIG.9andFIG.11are only exemplary examples for explaining embodiments of the present invention, and are not intended to limit the scope claimed in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following embodiments are not intended to limit the invention to be claimed to a specific environment, application, structure, process, or situation. In the attached drawings, elements unrelated to the invention to be claimed will be omitted. In the attached drawings, dimensions of and dimensional scales among individual elements are provided only as exemplary examples, and are not intended to limit the invention to be claimed. The same element symbols in the follow description may refer to the same elements unless otherwise specified.

Terminology described herein is only for ease of description of the content of the embodiments, and is not intended to limit the invention to be claimed. Unless otherwise specified clearly, singular forms “a” or “an” shall be deemed to include the plural forms as well. Terms such as “including”, “comprising” and “having” are used to specify the existence of features, integers, steps, operations, elements, components and/or groups stated after the terms, but do not exclude the existence or addition of one or more other additional features, integers, steps, operations, elements, components and/or groups or the like. The term “and/or” is used to indicate any one or all combinations of one or more related items enumerated. When the terms “first”, “second” and “third” are used to describe elements, the terms are not intended to limit but only distinguish these described elements. Therefore, for example, a first element may also be named as a second element without departing from the spirit or scope of the invention to be claimed.

Please refer toFIG.1, which demonstrates a probe system1. The probe system1may at least comprise a probe card11and a chuck12. The probe card11may be used to electrically connect and/or mechanically contact a device under test10and to test the electrical performance of the device under test10. The probe card11may be configured to test the device under test10. The device under test10may be semiconductor wafers. The chuck12may be used to support the device under test10for probing by the probe card11. The device under test10may comprise one or more contact pads (e.g., a contact pad101shown inFIG.1) such that the probe tip is configured to contact the one or more contact pads during testing of the device under test10.

The probe card11may comprise a circuit board111, a space transformer112, and a probe head113. The space transformer112may be disposed on the circuit board111, and the probe head113may be disposed on the space transformer112. The probe head113may basically comprise a plurality of probes and at least one guide plate, and one end of each probe may be electrically connected with the circuit board111through the space transformer112, and the other end of each probe may be in contact with a contact pad (e.g., a metal pad or a conductor bump) on the device under test10during testing. It shall be noted that the above-mentioned space transformer112is described as being disposed on the circuit board111simply according to the conventional dimensional relationship between the space transformer112and the circuit board111, and it is not intended to limit that the space transformer112must be located above the circuit board111in the physical sense.

The testing apparatus13may perform various test procedures and/or communicate test information to the device under test through the probe card11. The testing apparatus13may be, for example, a test head of a prober. In some test methods, there may be a Loopback test, the Loopback test uses the device under test10itself to generate a required high-frequency test signal, and the high-frequency test signal after passing through the probe card11is sent back to the device under test10for testing so as to determine whether the device under test works normally.

The circuit board111comprises a wafer side and a tester side. The wafer side of the circuit board111and the tester side of the circuit board111are disposed opposite to each other, and the tester side of the circuit board111is used for connecting a testing apparatus. In this embodiment, when the probe card11is used in the testing apparatus, the wafer side may be the lower side of the circuit board111which may face the space transformer112and/or the device under test, while the tester side may be the upper side of the circuit board111which may face away from the device under test and/or face the testing apparatus. In this embodiment, a general printed circuit board is adopted as the circuit board111, the circuit board111has a top surface, a bottom surface and a variety of signal lines located therein, and contact pads electrically connected with the signal lines are formed on the top surface and the bottom surface. The contact pad on the top surface of the circuit board111is touched through the pogo pin of the testing apparatus. The test signal of the testing apparatus may be transmitted to the bottom surface of the circuit board111through the signal lines described above.

The space transformer112also comprises a wafer side and a tester side. Here it shall be noted that, the space transformer112may be composed of a multilayer circuit board. The tester side of the space transformer112is connected to the wafer side of the circuit board111. In this embodiment, when the probe card11is used in the testing apparatus, the wafer side may be the lower side of the space transformer112which may face the probe head113and/or the device under test, while the tester side may be the upper side of the space transformer112which may face away from the device under test, face the circuit board111, and/or face the testing apparatus. In this embodiment, the space transformer112comprises a multilayer organic (MLO) carrier or a multilayer ceramic (MLC) carrier, and the material thereof may be adjusted according to actual needs, which is not limited in the present invention. The space transformer112is provided with a variety of signal lines therein, and contact pads electrically connected with the internal signal lines thereof are formed on the top surface and the bottom surface of the space transformer112, and the spacing between contact pads on the top surface is greater than the spacing between the contact pads on the bottom surface. The space transformer112is mechanically arranged on and electrically connected with the wafer side of the circuit board111(i.e., the bottom surface of the circuit board111) and is located below the circuit board111so that the contact pads on the top surface of the space transformer112may be electrically connected with the contact pads on the bottom surface of the circuit board111, and thus the signal lines inside the space transformer112are electrically connected with the signal lines of the circuit board111. Here it shall be noted that, the space transformer112may also be mechanically arranged on and/or electrically connected with the wafer side of the circuit board111indirectly through another carrier (for example, a raised board) disposed between the space transformer112and the circuit board111.

The probe head113may be mechanically arranged on and/or electrically connected with the wafer side of the space transformer112. As shown inFIG.1, the probe head113is in the form of a probe holder, and the probe head113comprises an upper guide plate unit113a, a lower guide plate unit113band a plurality of probes. The upper guide plate unit113amay comprise at least one upper guide plate, and the at least one upper guide plate may be provided with a plurality of upper guide holes. The lower guide plate unit113bmay comprise at least a lower guide plate, and the at least lower guide plate may be provided with a plurality of lower guide holes. The upper guide plate unit113aand the lower guide plate unit113bmay be vertically arranged opposite to each other along a longitudinal development axis (e.g., substantially along the direction of the coordinate axis Z (hereinafter referred to as “Z axis” for short) of the local reference system inFIG.1). Each probe passes through one of the plurality of upper guide holes and one of the plurality of lower guide holes.

As shown inFIG.1, each probe may comprise a first end (e.g., an end115inFIG.1), a second end (e.g., an end114inFIG.1) and a probe body (e.g., a probe body116inFIG.1) located between the first end and the second end. The first end may be the pinhead which ends at a contact tip, and the first end may be configured to abut a contact pad of the device under test10integrated in the semiconductor wafer. For example, the end115shown inFIG.1is configured to abut a contact pad101of the device under test10. The pin bottom of each probe may pass through the upper guide hole of the upper guide plate unit to be electrically connected with the space transformer112. The second end may be the pin bottom which ends at a contact bottom, and the second end may be configured to abut a contact pad of the space transformer112. The probe body may be a pin body extending basically along the longitudinal development axis between the first end and the second end. The pinhead of each probe is used to make electrical contact with the device under test. The pinhead of each probe may be configured for electrical and/or contact communication with the corresponding contact pad of the device under test. In some examples, communication means that the probe may be configured to transmit test signals of the probe card11to the device under test10and/or receive signals from the device under test10.

Many embodiments of the present invention relate to different embodiments of the probe head113and the guide plate structure in the probe head113. It shall be noted, however, that although the probes and the guide plate structures in various embodiments of the present invention may vary slightly, the plurality of probes contained in the probe heads in various embodiments generally may all include at least one probe pair, and each probe pair may be used to transmit a group of differential signals, that is, the probe pair is a differential pair. In a preferred embodiment of the present invention, the differential pair is used to transmit differential signals. That is, two single-ended signal lines (e.g., a P line and a N line) are used to connect TX+ and RX+, and TX− and RX− respectively to transmit signals at the same time, and these two signals have the same signal voltage amplitude but opposite signal phases (i.e., one with the positive signal phase and the other with the negative signal phase). That is, these two signal lines are mutually referenced, in which the P line refers to the N line, the N line refers to the P line, and the P line and the N line are ideally mutual reference loops.

Additionally, although the probes are depicted as straight probes inFIG.1, this is not a direct limitation on the type of probes applicable to the present invention. In fact, the probes applicable to the present invention may at least include straight probes (as illustrated inFIG.1toFIG.5, whereinFIG.2toFIG.5illustrate the assembled state of a straight probe offset from a flat plate) or pre-bent probes (as illustrated inFIG.6toFIG.9) or the like form. More specifically, the straight probe may be, for example, a Forming wire (FW), a MEMS wire (MW), or a pogo pin or the like. The pre-bent probe may be, for example, a Cobra probe or a MEMS body pre-bent forming wire or the like.

The so-called vertical probe head type basically comprises a plurality of contact probes held by at least one pair of flat plates (guide plates) or flat plate-like guides which are substantially parallel to each other. The flat plate-like guides may be provided with specific holes (e.g., guide holes or guide holes) and may be configured to be separated from each other by a specific distance, so as to reserve a free space or an air gap117for the contact probe to move and possibly deform. This pair of guide plates especially comprises an upper guide plate and a lower guide plate, both of which are provided with individual guide holes, and the contact probes pass through the guide holes in an axially slidable manner, and the probes are usually made of special metals with good electrical and mechanical properties. A good connection between the contact probe and the contact pad of the device under test is ensured by pressing the test head on the component itself. During pressurized contact, the probe may be slidably contacted inside the guide holes in the upper and lower guide plates, which causes bending in the air gap between the two guide plates and causing sliding inside the guide holes.

In addition, the bending of the contact probes (e.g., the forming wire or the MEMS wire among straight probes as illustrated inFIG.2toFIG.5) in the air gap may be assisted by properly configuring the probes themselves (such as the pre-bent probes as illustrated inFIG.6toFIG.9) or the guide plates thereof. InFIG.2toFIG.5, in order to simplify the explanation, only some contact probes among a plurality of probes usually contained in a test head are depicted in the figure, and the test head is of the so-called offset flat plate type (which is suitable for the forming wire or the MEMS wire among the straight probes). Specifically, the respective centers of the upper guide holes and the lower guide holes corresponding to each other may be misaligned with each other, that is, the center connecting line between the upper guide hole and the lower guide hole is not parallel to a longitudinal direction. The longitudinal direction may be direction parallel to the Z axis in the local reference system of the drawing, and it is perpendicular to a reference plane118. The reference plane118may correspond to a horizontal development plane of the guide plates. Accordingly, the contact probes accommodated in the guide holes of the upper guide plate and the lower guide plate are deformed with respect to a longitudinal development axis thereof (corresponding to the Z-axis direction of the local reference system of the drawing), and the longitudinal development axis is set to be perpendicular to the reference plane118. The upper guide plate and the lower guide plate may be parallel to each other and extend along the reference plane118, and the semiconductor wafer, the device under test10and the plates of the space transformer112may also develop along the reference plane118.

When the probe in the vertical probe head is of a pre-bent probe type, e.g., in the example of a test head made of Cobra in the prior art, as shown inFIG.6toFIG.9, the contact probe will have a pre-deformed configuration with an offset between the contact tip portion and the contact bottom portion which have been defined in the placement conditions of the probe head. Especially in this example, the contact probe comprises a pre-deformed part, which may assist the proper bending of the contact probe even when the test head is not in contact with the device under test. The contact probe is further deformed during its operation, i.e., when it is pressed to contact the device under test. It shall be noted that for proper probe head operation, the contact probe may have proper freedom of axial movement inside the guide holes. In this way, these contact probes may also be extracted and replaced when a single probe fails, without being forced to replace the entire probe head. The freedom of axial movement (especially when the probe slides inside the guide hole) is in contrast with the normal safety requirements of the probe head during its operation.

Please refer toFIG.2. A first embodiment of the present invention is a probe head20and a guide plate structure thereof. The probe head20may be used to replace the probe head113shown inFIG.1. The probe head20may be mechanically arranged on and/or electrically connected with the wafer side of the space transformer112. The probe head20may comprise an upper guide plate unit, a lower guide plate unit and a plurality of probes. The upper guide plate unit may comprise at least one upper guide plate, such as an upper guide plate201shown inFIG.2. The lower guide plate unit may comprise at least a lower guide plate, such as a lower guide plate202shown inFIG.2. Hereinafter, the at least one upper guide plate included in the upper guide plate unit and the at least one lower guide plate included in the lower guide plate unit will be exemplified by the upper guide plate201and the lower guide plate202, respectively.

The upper guide plate201may be provided with a plurality of upper guide holes, while the lower guide plate202may be provided with a plurality of lower guide holes. The upper guide plate201and the lower guide plate202may be vertically arranged opposite to each other along a longitudinal development axis (substantially along the Z-axis direction of the local reference system in the figure).

The probe head20may further comprise a plurality of probes, such as a probe pair203and a probe pair204shown inFIG.2for transmitting differential signals in pairs. Each probe passes through one of the plurality of upper guide holes and one of the plurality of lower guide holes. In addition, each probe may comprise a first end, and the first end may end at a contact tip and may be configured to abut a contact pad of the device under test10. For example, an end205shown inFIG.2is configured to abut a contact pad101of the device under test10. Each probe may further comprise a second end (e.g., an end206shown inFIG.2), and the second end may end at a contact bottom and may be configured to abut a corresponding contact pad of the space transformer112.

Each probe may further comprise a probe body extending between the first end and the second end according to a longitudinal development axis. For example, a probe body207shown inFIG.2extends between the end205and the end206according to a longitudinal development axis. Each probe body may have a transverse diameter, which is an extension of the cross section of the probe and/or a maximum transverse dimension of a cross section. The cross section is not necessarily a circle, and may be taken from a plane perpendicular to the longitudinal development axis (that is, perpendicular to the Z-axis direction in the figure). The probe body preferably has a square or rectangular cross section. According to some embodiments of the present invention, the probe may be a probe that is called a “buckling beam” in the art. That is, the probe has a constant and preferably square or rectangular cross section over its entire length, wherein the probe body is deformed and suitable for bending at a substantially central position, and thus the probe body is further deformed during the testing of the device under test.

The upper guide plate201and the lower guide plate202may be separated by a distance, and may each comprise a plurality of guide holes corresponding to the plurality of probes so as to slidably accommodate a probe in each guide hole, and the guide holes accommodating the same probe in the upper guide plate201and the lower guide plate202correspond to each other. In practical application, the upper guide plate201and the lower guide plate202may be offset on the XY plane to assist the contact probe to bend in the air gap. InFIG.2, in order to simplify the explanation, only some of multiple probes usually included in a probe head20are depicted in the figure.

As shown inFIG.2, the upper guide plate201may comprise a guide-hole pair208, while the lower guide plate202may comprise a guide-hole pair209. The guide-hole pair208and the guide-hole pair209may be used to accommodate the probe pair203. Similarly, the upper guide plate201may further comprise another guide-hole pair210, while lower guide plate202may comprise another guide-hole pair211, and the guide-hole pair210and the guide-hole pair211may be used to accommodate the probe pair204. In some embodiments, each guide hole in the guide-hole pair208and/or the guide-hole pair209may be substantially circular. In some embodiments, each guide hole in the guide-hole pair208and/or the guide-hole pair209may be substantially polygonal, such as rectangular, trapezoidal, parallelogram-shaped or the like. In addition, in some embodiments where the guide holes are polygonal, the guide-hole pair208and/or the guide-hole pair209may also each be arranged with the shortest sides of the polygons opposite to each other. That is, the guide-hole pair208and/or the guide-hole pair209may each be arranged with the width sides opposite to each other when taking the rectangular guide holes as an example.

In this embodiment, the probe pair203and/or the probe pair204are a differential pair that transmits a group of differential signals. In order to reduce the impedance fluctuation caused when the probe pair203transmits the differential signals, the area between the guide-hole pair209in the lower guide plate202(indicated by cross lines in the figure) may have a first material and/or the area between the guide-hole pair208in the upper guide plate201(indicated by diagonal lines in the figure) may have a second material. Similarly, the area between the guide-hole pair211in the lower guide plate202(indicated by cross lines in the figure) may have the first material and/or the area between the guide-hole pair210in the upper guide plate201(indicated by diagonal lines in the figure) may have the second material. InFIG.2, although the area between the guide-hole pair209is shown as extending along the direction of a coordinate axis X (hereinafter referred to as “X axis” for short) of the local reference system, in some embodiments, the area between the guide-hole pair209may also extend along the direction of a coordinate axis Y (hereinafter referred to as “Y axis” for short) of the local reference system. That is, when the differential pairs are arranged at intervals along the X-axis direction and the buckling direction of the probe is the X-axis direction (as illustrated inFIG.2), the area between the guide-hole pair209may be defined as extending along the X-axis direction; and when the differential pairs are arranged at intervals along the Y-axis direction and the buckling direction of the probe is still the X-axis direction, the area between the guide-hole pair209may be defined as extending along the Y-axis direction.

At least one of the first material and the second material may have a relative dielectric constant not greater than 6, so as to reduce a return loss between the probe head20and the device under test10, that is, to improve the degree of impedance matching between the probe head20and the device under test10. That is, the first material and the second material are configured to provide a compensating impedance between the guide-hole pairs208,209,210and211, and the compensating impedance is used to improve the impedance matching when probing the device under test with the probe pairs203and204. Furthermore, in some embodiments, the first material in the lower guide plate202and/or the second material in the upper guide plate201may even have a relative dielectric constant not greater than 4. For example, the first material and the second material may be ceramics, porous ceramics, ceramic matrix composite or engineering plastics respectively, and the second material may be different from the first material in some embodiments.

In some embodiments, the first material and/or the second material described above may be a composite material. That is, the first material and/or the second material with a relative dielectric constant not greater than 6 (or even not more than 4) may be composed of multiple materials.

In some embodiments, a thickness t2of the lower guide plate202may be not less than a thickness t1of the upper guide plate201. For example, when the thickness t2of the lower guide plate202is greater than the thickness t1of the upper guide plate201, better support can be obtained when the probe slides and moves in the guide-hole pair209and the guide-hole pair211, so that the probe can slide and move up and down in the guide-hole pair209and the guide-hole pair211more smoothly. However, in some embodiments, the thickness of the upper guide plate201may be not less than that of the lower guide plate202.

The probe pair203, the probe pair204, and other probes in the probe head20may all be in the form of straight probes. In some embodiments, the spacing between the corresponding centers of the probe pair203may have a first relative distance P1. The first relative distance P1may range from 80 micrometers to 220 micrometers, and preferably from 100 micrometers to 130 micrometers. Similarly, in some embodiments, the spacing between the corresponding centers of the probe pairs204may have a second relative distance P2. The second relative distance P2may also range from 80 micrometers to 220 micrometers, and preferably from 100 micrometers to 130 micrometers.

Specifically, the first relative distance P1may be a center spacing corresponding to the first end (the contact tip) of the probe pair203or a center spacing corresponding to the second end (the contact bottom) of the probe pair203, and it corresponds to a center spacing of the corresponding groups of contact pads in the device under test10. In some embodiments, the center spacing corresponding to the first end (the contact tip) of the probe pair203may be equal to the center spacing corresponding to the second end (the contact bottom) of the probe pair203. Similarly, the second relative distance P2may be a center spacing corresponding to the first end (the contact tip) of the probe pair204or a center spacing corresponding to the second end (the contact bottom) of the probe pair204, and it corresponds to a center spacing of the corresponding groups of contact pads in the device under test10. In some embodiments, the center spacing corresponding to the first end (the contact tip) of the probe pair204may be equal to the center spacing corresponding to the second end (the contact bottom) of the probe pair204. In some embodiments, the center spacing of the respective groups of contact pads corresponding to the respective probe pairs in the device under test10may be a third relative distance P3, and the first relative distance P1and/or the second relative distance P2may be smaller than the third relative distance P3.

In some embodiments, the probe length of the respective probe pairs in the probe head20according to the longitudinal development axis may range between 3 millimeters and 7 millimeters. In some embodiments, the probe length may also be not greater than 6 millimeters or even preferably not greater than 4 millimeters.

In some embodiments, the thickness of the contact tip of each of the probe pair203, the probe pair204and other probe pairs in the probe head20in a direction of a probe-center-connecting line (e.g., a direction D1of a probe-center-connecting line corresponding to the probe pair203as illustrated inFIG.2) corresponding to the respective probe pairs may be greater than the thickness of the remaining parts of the first end (i.e., other parts except for the contact tip) in the direction of a probe-center-connecting line, and even further greater than the thickness of the probe body (the pin body) in the direction of a probe-center-connecting line in some embodiments. In order to achieve this result, the contact tip may be thickened in the production process (for example, the contact tip is entirely covered and thickened as a whole, or the contact tip is only partially thickened in the direction of a probe-center-connecting line), but the way in which the contact tip is thickened is not limited to electroplating. For example, for MEMS wires, the thickness of the contact tip may be increased through the MEMS process. When the contact tips of the probe pairs203,204are thickened, the contact areas thereof with the contact pads of the device under test will also be increased, thereby providing a more stable contact mode. Especially, when the return loss between the probe head and the device under test is reduced for impedance matching, the spacing between the corresponding centers of the probe pair203is reduced, that is, the first relative distance P1is reduced to be less than the third relative distance P3, and at this point, the thickened contact tip can still normally contact the contact pad.

In some embodiments, when the probe is a pre-bent (e.g., Cobra) probe (as described later forFIG.6toFIG.9), the width of the probe body may still be greater than the thickness of the thickened contact tip because the probe body is processed by stamping in the production process, so as to prevent the probe from slipping out of the guide hole of the guide plate. The thickness of the thickened contact tip may be greater than or equal to a remaining part of the first end and/or the probe body preferably by 2% to 20%, and more preferably by 10%. The increase in thickness of the thickened contact tip may range from 1 to 5 micrometers, and preferably may range from 1 to 2 micrometers. Taking the case where the contact tip is thickened (that is, the diameter is increased) by electroplating (e.g., in the case of Cobra) as an example, when the thickness of the first end of the probe is 50 micrometers, a thickness of 1 to 2 micrometers may be formed at the contact tip, and at this point, the thickness of the thickened contact tip is 52 to 54 micrometers.

Please refer toFIG.3. A second embodiment of the present invention is a probe head30and a guide plate structure thereof. In the probe head20shown inFIG.2, the lower guide plate202and/or the upper guide plate201only have the first material or the second material in the area between the respective guide-hole pair. However, the probe head30shown inFIG.3differs from the probe head20in that an entire lower guide plate302included in the probe head30may have the first material and/or an entire upper guide plate301included in the probe head30may have the second material.

The upper guide plate301may comprise a guide-hole pair303, while the lower guide plate302may comprise a guide-hole pair304. The guide-hole pair303and the guide-hole pair304may also be used to accommodate the probe pair203. Similarly, the upper guide plate301may further comprise another guide-hole pair305, while the lower guide plate302may comprise another guide-hole pair306, and the guide-hole pair305and the guide-hole pair306may be used to accommodate the probe pair204.

Please refer toFIG.4. A third embodiment of the present invention is a probe head40and a guide plate structure thereof. The probe head PH3differs from the probe heads20and30in that the probe head40may have the first material or the second material only in the area between each guide-hole pair on one included guide plate (as in the case of the upper and lower guide plates shown inFIG.2), and may have the first material or the second material on the entirety of another included guide plate (as in the case of the upper and lower guide plates shown inFIG.3). In other words, the distribution of the first material and the second material among the two guide plates may be different.FIG.4illustrates one case in which the probe head40may adopt the upper guide plate301in the probe head30as its upper guide plate and adopt the lower guide plate202in the probe head20as its lower guide plate.

Please refer toFIG.5. A fourth embodiment of the present invention is a probe head50and a guide plate structure thereof. The probe head50differs from other embodiments previously described in that it comprises at least one multilayer guide plate. The multilayer guide plate may have at least a first layer and a second layer, and an air layer may be interposed between the first layer and the second layer. Each probe in the probe head50may penetrate through the first layer, the air layer and the second layer.FIG.5illustrates one case in which the probe head50may adopt the upper guide plate301in the probe head30as its upper guide plate and may comprise a multilayer lower guide plate501. The lower guide plate501may have a guide-hole pair502, a guide-hole pair503, a first layer504and a second layer505, and an air layer506may be interposed between the first layer504and the second layer505. The air layer506may be formed by separating the first layer504from the second layer505by a frame507(indicated by horizontal lines in the figure) of the lower guide plate501. The guide-hole pair502and the guide-hole pair503may penetrate through the first layer, the air layer and the second layer, while the probe pair203and the probe pair204may penetrate through the guide-hole pair502and the guide-hole pair503respectively. However, the multilayer guide plate is not limited to comprising two layers, and the probe head50is not limited to comprising one multilayer guide plate. That is, in some embodiments, both the upper and lower guide plates of the probe head50may be multilayer guide plates, and each multilayer guide plate may comprise more than two layers.

In addition, in some embodiments, the multilayer guide plate may have the first material or the second material only in the area between each guide-hole pair, just like the guide plate in the probe head20. However, in some embodiments, the multilayer guide plate may have the first material or the second material on the entirety of the first layer and the second layer, just like the guide plate in the probe head30.

Please refer toFIG.6. A fifth embodiment of the present invention is a probe head60and a guide plate structure thereof. The probes included in the probe head shown inFIG.2toFIG.5are all straight probes, while a plurality of probes included in the probe head60may be pre-bent probes (e.g., a probe pair601and a probe pair602shown inFIG.6for transmitting differential signals in pairs). Each probe passes through one of a plurality of upper guide holes and one of a plurality of lower guide holes. In addition, each probe may comprise a first end, and the first end may end at a contact tip and may be configured to abut a contact pad of the device under test10. For example, an end603shown inFIG.6is configured to abut a contact pad101of the device under test10. Each probe may further comprise a second end (e.g., an end604shown inFIG.6), and the second end may end at a contact bottom and may be configured to abut a corresponding contact pad of the space transformer112.

Each probe may further comprise a probe body extending between the first end and the second end according to a longitudinal development axis. For example, a probe body605shown inFIG.6extends between the end603and the end604according to a longitudinal development axis. Each probe body may have a transverse diameter, which is an extension of the cross section of the probe and/or a maximum transverse dimension of a cross section. The cross section is not necessarily a circle, and may be taken from a plane perpendicular to the longitudinal development axis (that is, perpendicular to the Z-axis direction in the figure). The probe body preferably has a square or rectangular cross section, and the probe body may have a flat shape because it has been processed by stamping in the production process.

For the guide plate structure included in the upper guide plate201and the lower guide plate202in order to reduce the impedance fluctuation caused when the probe pair601and the probe pair602transmit differential signals, reference may be made to the contents described for the probe head20, and this will not be further described herein. In some embodiments, the spacing between the corresponding centers of the probe pair601may have a fourth relative distance P4. The fourth relative distance P4may range from 80 micrometers to 220 micrometers, and preferably from 100 micrometers to 130 micrometers. Similarly, in some embodiments, the spacing between the corresponding centers of the probe pair602may have a fifth relative distance P5. The fifth relative distance P5may also range from 80 micrometers to 220 micrometers, and preferably from 100 micrometers to 130 micrometers. Specifically, the fourth relative distance P4may be a center spacing corresponding to the first end (the contact tip, e.g., the end603shown inFIG.6) of the probe pair601or a center spacing corresponding to the second end (the contact bottom, e.g., the end604shown inFIG.6) of the probe pair601, and it corresponds to a center spacing (e.g., the third relative distance P3) of the corresponding groups of contact pads in the device under test10. In some embodiments, the center spacing corresponding to the first end (the contact tip) of the probe pair601may be equal to the center spacing corresponding to the second end (the contact bottom) of the probe pair601. Similarly, the fifth relative distance P5may be a center spacing corresponding to the first end (the contact tip) of the probe pair602or a center spacing corresponding to the second end (the contact bottom) of the probe pair602, and it corresponds to a center spacing (for example, the third relative distance P3) of the corresponding groups of contact pads in the device under test10. In some embodiments, the center spacing corresponding to the first end (the contact tip) of the respective probe pairs may be equal to the center spacing corresponding to the second end (the contact bottom). In some embodiments, the center spacing of the respective groups of contact pads corresponding to the respective probe pairs in the device under test10may be a third relative distance P3, and the fourth relative distance P4and/or the fifth relative distance P5may be smaller than the third relative distance P3.

Please refer toFIG.7. A sixth embodiment of the present invention is a probe head70and a guide plate structure thereof. In the probe head60shown inFIG.6, the lower guide plate202and/or the upper guide plate201have the first material or the second material only in the areas between the respective guide-hole pairs. However, the probe head70differs from the probe head60in that, the probe head70may comprise the upper guide plate301and the lower guide plate302described previously for the probe head30, wherein the whole lower guide plate302may have the first material and/or the whole upper guide plate301may have the second material.

Please refer toFIG.8. A seventh embodiment of the present invention is a probe head80and a guide plate structure thereof. Similar to the probe head40, the probe head80differs from the probe heads60and70in that the probe head80may have the first material or the second material only in the area between each guide-hole pair on one included guide plate, and may have the first material or the second material on the entirety of another included guide plate. In other words, the distribution of the first material and the second material among the two guide plates may be different.FIG.8illustrates one case in which the probe head80may adopt the upper guide plate301previously described for the probe head30as its upper guide plate and adopt the lower guide plate202previously described for the probe head20as its lower guide plate.

Please refer toFIG.9. An eighth embodiment of the present invention is a probe head90and a guide plate structure thereof. The probe head90differs from the aforementioned fifth to seventh embodiments in that it comprises at least one multilayer guide plate.FIG.9illustrates one case in which the probe head90may adopt the upper guide plate201previously described for the probe head20as its upper guide plate and may adopt the lower guide plate501previously described for the probe head50as its lower guide plate. However, the probe head90is not limited to only comprising one multilayer guide plate. That is, in some embodiments, both the upper and lower guide plates of the probe head90may be multilayer guide plates. The multilayer guide plate may have a first layer and a second layer, and an air layer may be interposed between the first layer and the second layer. Each probe in the probe head90may penetrate through the first layer, the air layer and the second layer.

In addition, in some embodiments, the multilayer guide plate may have the first material or the second material only in the area between the respective guide-hole pairs, just like the guide plates in the probe head20the probe head60. However, in some embodiments, the multilayer guide plate may also have the first material or the second material on the entirety of the first layer and the second layer, just like the guide plates in the probe head30and the probe head70.

For the technical requirements as described above for the prior art, both electrical and mechanical characteristics should be considered during the designing of the probe head. In particular, the guide plate in the probe head needs to bear the force generated by elements such as the probe and/or the space transformer during the test, and thus it is required to meet the requirements of both electrical and mechanical characteristics during the test as much as possible, so as to avoid the damage (for example, the cracking of the guide hole, or chipping due to friction during the test) caused by the force exerted by the probe on the wall of the guide hole after the assembly is offset from the flat plate, which otherwise would affect the result of the testing. Therefore, after considering both improving the degree of impedance matching between the probe head20and the device under test10and improving the mechanical characteristics of the guide plate, the present invention proposes a solution of making the material of the guide plate have a relative dielectric constant not greater than 6 (or even not more than 4). In addition, in some embodiments, especially when the device under test needs high-frequency/high-speed testing, in order to take both the electrical and mechanical characteristics of the guide plate into account, the probe head form of a guide plate material with a relative dielectric constant not greater than 6 (or even not more than 4) in combination with a pre-bent probe (such as a Cobra probe or a MEMS body pre-bent forming wire, etc.) may be selected. Because offset of the guide plates are not required for the pre-bent probe, the force exerted by the probe on the wall of the guide hole may be greatly reduced. In this case, the electrical requirements for high-frequency/high-speed testing can be met, and meanwhile the requirements for mechanical characteristics of the guide plates can be slightly reduced.

Next, please refer toFIG.10andFIG.11together.FIG.10is an eye diagram when a device under test is tested based on a guide plate structure in the prior art (i.e., without using a material with a low relative dielectric constant), andFIG.11is an eye diagram when a device under test is tested based on a guide plate structure according to one or more embodiments of the present invention (i.e., using a material with a low relative dielectric constant generally speaking). InFIG.10, the eye height is about 188 millivolts (mV) and the eye width is about 7.82 picoseconds (ps). InFIG.11, the eye height is 252 millivolts and the eye width is about 9.10 picoseconds. As compared toFIG.10, the eye height inFIG.11is improved by 1.34 times, and the eye width is improved by 1.16 times. As can be clearly seen by comparing the two figures, the material with a low relative dielectric constant provided according to the present invention is used as the guide plate material between a pair of probes corresponding to a group of differential signals, which effectively reduces the impedance fluctuation caused by the guide plate between the pair of probes, thereby reducing the return loss between the probe head as a whole and the device under test. That is, the impedance matching between the probe head (even the probe card to which the probe head belongs) as a whole and the device under test is improved, thereby improving the signal integrity.