1. Technical Field
The present invention relates generally to the structure of a probe card, and more particularly to a probe card, and its connecting circuit board and signal feeding structure.
2. Description of Related Art
To test if every electronic component of a device-under-test (DUT) is electrically connected correctly, a widely used method is to apply a probe card between a test machine and the DUT, wherein the probe card is functioned as a transmission interface of test signals. In order to have accurate test results, the impedance of a probe card has to match that of the test machine and the DUT to effectively transmit high-frequency test signals.
The impedance matching between a probe card, a test machine, and a DUT can be affected by many factors such as the structural differences between different kinds of probe cards. Typically, the factors which mostly affect the impedance matching are related to the difference between the diameter of a probe and the width of the pad on a circuit board. When an electrical signal is transmitted to a probe from a circuit board, it may be interfered due to the difference between the probe diameter and the width of the pad, and such problem may lead to disorder among electrical signals, and therefore the loss rate may increase, while the accuracy of test may decrease as well.
In view of the above, the primary objective of the present invention is to provide a probe card, and a connecting circuit board and a signal feeding structure of the probe card, which is helpful to transmit electrical signals more smoothly without letting the electrical signals interfere each other or become disorder. The accuracy of transmitting electrical signals can be increased as a result, and therefore the goal of impedance matching can be effectively achieved.
The present invention provides a probe card, which is adapted to be provided between a DUT and a test machine, including a connecting circuit board, a connector, and a probe. The connecting circuit board includes a substrate, a signal feeding structure, and a connecting layer, wherein the substrate has a first surface and a second surface, and the substrate has a plurality of ground vias and a signal via which communicate the first surface and the second surface; the signal feeding structure is made of a conductive material, and is disposed on the first surface of the substrate; the signal feeding structure comprises a ground pad and a signal feeding pad, wherein the ground pad is connected to the plurality of ground vias, and has a matching compensation opening; the matching compensation opening has a first side and a second side, wherein a width of the first side is less than a width of the second side; the signal feeding pad is located in the matching compensation opening without contacting the ground pad; the signal feeding pad has a first end and a second end, wherein the first end is toward the first side, while the second end is toward the second side, and is connected to the signal via; a width of the second end is greater than a width of the first end, and is no less than an aperture of the signal via; a first distance is formed between the first end a wall of the first side, and a second distance is formed between the second end and a wall of the second side, wherein the second distance is longer than the first distance; the connecting layer is made of a conductive material, and is disposed on the second surface of the substrate, wherein the connecting layer has a signal connecting portion and a ground connecting portion which are mutually separated; the signal connecting portion is connected to the signal via, and the ground connecting portion is connected to the plurality of ground vias. The connector is disposed on the connecting layer, wherein the connector is adapted to be electrically connected to the test machine, and has a signal transmitting portion and a ground transmitting portion; the signal transmitting portion is connected to the signal connecting portion, and the ground transmitting portion is connected to the ground connecting portion of the connecting layer. The probe has a point end and a connect end, wherein the point end is adapted to touch the DUT, and the connect end is connected to the first end of the signal feeding pad; a diameter of the connect end is no greater than the width of the first end.
The present invention further provides a connecting circuit board, which is adapted to be provided between a probe and a connector, wherein the probe has a connect end, and the connector has a signal transmitting portion and a ground transmitting portion. The connecting circuit board includes a substrate, a signal feeding structure, and connecting layer. The substrate has a first surface and a second surface, wherein the substrate has a plurality of ground vias and a signal via which communicate the first surface and the second surface. The signal feeding structure is made of a conductive material, wherein the signal feeding structure is disposed on the first surface of the substrate; the signal feeding structure comprises a ground pad and a signal feeding pad, wherein the ground pad is connected to the plurality of ground vias, and has a matching compensation opening; the matching compensation opening has a first side and a second side, wherein a width of the first side is less than a width of the second side; the signal feeding pad is located in the matching compensation opening without contacting the ground pad; the signal feeding pad has a first end and a second end, wherein the first end is toward the first side, and is adapted to be connected to the connect end of the probe; a width of the first end is no less than a diameter of the connect end; the second end is toward the second side, and is connected to the signal via; a width of the second end is greater than a width of the first end, and is no less than an aperture of the signal via; a first distance is formed between the first end a wall of the first side, and a second distance is formed between the second end and a wall of the second side, wherein the second distance is longer than the first distance. The connecting layer is made of a conductive material, wherein the connecting layer is disposed on the second surface of the substrate, wherein the connecting layer has a signal connecting portion and a ground connecting portion which are mutually separated; the signal connecting portion is connected to the signal via and the signal transmitting portion, and the ground connecting portion is connected to the plurality of ground vias and the ground transmitting portion.
The present invention further provides a signal feeding structure, which is adapted to connect a connect end of a probe and a signal via of a substrate, including a ground pad and a signal feeding pad. The ground pad is made of a conductive material, wherein the ground pad is disposed on the substrate, and has a matching compensation opening which goes through the ground pad; the matching compensation opening has a first side and a second side, wherein a width of the first side is less than a width of the second side. The signal feeding pad is made of a conductive material, wherein the signal feeding pad is disposed on the substrate and is in the matching compensation opening without contacting the ground pad; the signal feeding pad has a first end and a second end, wherein the first end is toward the first side, and is adapted to be connected to the connect end of the probe; a width of the first end is no less than a diameter of the connect end; the second end is toward the second side, and is connected to the signal via; a width of the second end is greater than a width of the first end, and is no less than an aperture of the signal via; a first distance is formed between the first end a wall of the first side, and a second distance is formed between the second end and a wall of the second side, wherein the second distance is longer than the first distance.
Whereby, with the aforementioned design, electrical signals can be transmitted more smoothly without letting the electrical signals interfere each other or become disorder. As a result, the accuracy of transmitting electrical signals can be increased, and therefore the goal of impedance matching can be effectively achieved.
The present invention will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, in which
As shown in
As shown in
The signal feeding structure 14 is made of a conductive material, and is disposed on the first surface 121 of the substrate 12. As shown in
The signal feeding pad 142 is located in the matching compensation opening 143 without contacting the ground pad 141, and a shape thereof is similar to a shape of the matching compensation opening 143. An area of the signal feeding pad 142 is smaller than an area of the region surrounded by the ground vias 12. More specifically, the signal feeding pad 124 is located within a projection range of the region. In addition, as shown in
With the aforementioned design, a first distance D1 is formed between the first end 142a and a wall at the first side 143a, and a second distance D2 is formed between the second end 142b and the wall at the second side 143b, wherein the second distance D2 is greater than the first distance D1. In the first preferred embodiment, the distance between the signal feeding pad 142 and the wall of the matching compensation opening 143 is gradually narrower from the second end 142b to the first end 142a (i.e., from the second side 143b to the first side 143a).
Since the width of the signal feeding pad 142 is gradually narrower from the second end 142b toward the first end 142a, the parasitic inductance at each portion thereof gradually increases from the second end 142b toward the first end 142a. In addition, since the distance between the signal feeding pad 142 and the wall of the matching compensation opening 143 is gradually narrower from the second end 142b toward the first end 142a, the parasitic capacitance between the signal feeding pad 142 and the matching compensation opening 143 gradually increases from the second end 142b toward the first end 142a.
In this way, as it can be seen from the formula of impedance: Z=√(L/C) without taking resistance into account, if the parasitic capacitance C generated between the signal feeding pad 142 and the wall of the matching compensation opening 143 due to the distance therebetween changes in proportion to the parasitic inductance L generated by the width of the signal feeding pad 142, the corresponding impedance is instant, and therefore the impedance Z is equal at each portion of the present invention.
The connecting layer 16 is made of a conductive material, and is disposed on the second surface 122 of the substrate 12, wherein the connecting layer 16 has a signal connecting portion 161 and a ground connecting portion 162 which are mutually separated, as shown in
Two opposite ends of the probe 20 are a point end 22 and a connect end 24 respectively, wherein the point end 22 is adapted to touch a test portion of the DUT, and the connect end 24 is connected to the first end 142a of the signal feeding pad 142. In the first preferred embodiment, a diameter φ2 of the connect end 24 is no greater than the width W1 of the first end 142a, and is preferred to be slightly less than the width W1 of the first end 142a. Such design can not only prevent the problem of free welding during installation, but also prevent the problem of current disorder which may happen due to excessive difference between cross-sectional areas when electrical signals passing through where the connect end 24 and the first end 142a are connected, which allows current to flow through more smoothly.
The probe holder 30 is made of an insulating material, and is disposed on the substrate 10, wherein a portion of the probe 20 between the point end 22 and the connect end 24 is embedded in the probe holder 30, while the point end 22 and the connect end 24 are exposed out of the probe holder 30. The reason to provide the probe holder 30 in the present invention is to stabilize the probe 20. In addition, the probe holder 30 separates the probe 20 and other components, and therefore the probe 20 may have better efficiency on transmitting signals.
The connector 40 is disposed on the connecting layer 16, and is electrically connected to the test machine. The connector 40 has a signal transmitting portion 42 and a ground transmitting portion 44, wherein the signal transmitting portion 42 is a metal pin, and is connected to the signal connecting portion 161. In other words, the signal transmitting portion 42 is electrically connected to the probe 20 through the signal connecting portion 161, the signal via 123, and the signal feeding pad 142. The ground transmitting portion 44 is a metal holder surrounding the signal transmitting portion 42, and is connected to the ground connecting portion 162. Similarly, the ground transmitting portion 44 is electrically connected to the ground pad 141 through the ground connecting portion 162 and the plurality of ground vias 124.
With the aforementioned design, such as the width W1 of the first end 142a of the signal feeding pad 142 is slightly greater than the diameter φ2 of the probe connect end 24, the width W2 of the second end 142b of the signal feeding pad 142 is slightly greater than the aperture φ1, and the width of the signal feeding pad 142 is gradually narrower from the second end 142b toward the first end 142a, when an electrical signal passes through where the probe 20 and the first end 142a are connected and where the second end 142b and the signal via 123 are connected, the problem of current disorder which may happen due to excessive differences between cross-sectional areas can be prevented. Furthermore, since the width of the signal feeding pad 142 is gradually narrower, the signal feeding pad 142 may be served as a connecting interface, which allows electrical signals to pass therethrough more smoothly. As a result, the loss while transmitting electrical signals can be effectively reduced, and the accuracy of transmission can be enhanced as well.
In addition, since the matching compensation opening 143 is gradually narrower from the second side 143b toward the first side 143a, the distance between the signal feeding pad 142 and the wall of the matching compensation opening 143 is gradually narrower from the second end 142b toward the first end 142a, too. Therefore, the parasitic capacitance generated between the signal feeding pad 142 and the wall of the matching compensation opening 143 would change in proportion to the parasitic inductance generated along with the width of the signal feeding pad 142, which makes the impedance at each portion of the transmission path equal, and therefore effectively reaches the goal of impedance matching.
It is worth mentioning that, in addition to the aforementioned design, a signal feeding pad 542 and a matching compensation opening 543 of the second preferred embodiment can be gradually narrower in a ladder shape, as shown in
In addition, a signal feeding pad 642 and a ground pad 641 of the third preferred embodiment can be disposed on different layers of the substrate 62, as shown in
It must be pointed out that the embodiments described above are only some preferred embodiments of the present invention, and are not limitations of the present invention. For example, different ways of gradual narrowing mentioned in different preferred embodiments can be correspondingly modified to be adapted to be used for other designs which dispose the signal feeding pad and the ground pad either on the same layer or on different layers of the substrate. As long as the functions of impedance matching and conversion of connecting interfaces can be achieved by using the gradual narrowing shapes of the signal feeding pad and the matching compensation opening, all equivalent structures which employ the concepts disclosed in this specification and the appended claims should fall within the scope of the present invention.
Number | Date | Country | Kind |
---|---|---|---|
103124721 | Jul 2014 | TW | national |