Technical Field

The present invention relates to a contact pin holder used to test an electronic device such as a CPU or a memory, and in particular, relates to a contact pin holder having a coaxial transmission line for testing a semiconductor package.

Background

In carrying out an evaluation test of signal transmission property or the like of an electronic device such as a BGA (ball grid array) device, a contact pin holder, having contacts each connectable to each terminal of the electronic device, is used. In recent years, a frequency of a signal used in the electronic device becomes higher, as a processing speed of the electronic device becomes higher. Corresponding to such a high-speed signal, the contact pin holder is also required to transmit the high-speed signal.

In transmitting a signal (in particular, a high-speed signal), it is important to stabilize a characteristic impedance of a transmission line for transmitting the signal. To this end, a metallic block structure, provided with a coaxial transmission line having predetermined characteristic impedance, has been proposed.

For example, Patent Literature 1 describes that "a dielectric layer 15 is disposed on the periphery of a contact probe 10 via a second metallic film 16, and a first metallic film 17 is disposed on an outer surface of dielectric layer 15. Due to this, a capacitor 18 is formed between second metallic film 16 (movable pins 11, 12) and first metallic film 17 (a metallic sleeve 9)."

Patent Literature 2 describes that "a contact probe 21 for transmitting a high- frequency signal has annular probe holders 31 fixed to two parts on the periphery of contact probe 21, and probe holders 31 are fitted into a through hole 3 so that probe holders are positioned at upper and lower part of a metallic block 2. Due to this, a hollow portion is defined between contact probe 21 and metallic block 2, and a coaxial

transmission line, having contact probe 21 as an inner conductor and metallic block 2 as an outer conductor, is formed, which has desired characteristic impedance." Citation List

Patent Literature

PTL1 Japanese Unexamined Patent Publication (Kokai) No. 2005-49163

PTL2 Japanese Unexamined Patent Publication (Kokai) No. 2007-198835

Summary

In the prior art, a block or the like adapted to hold contact pins is manufactured from metal. Therefore, although it is easy to electrically connect each contact pin, the block is relatively heavy and hard to be handled. Further, it is difficult to sophisticate the metallic block as a contact pin holder, for example, it is impossible to provide a plurality of ground systems in the metallic block.

Thus, the invention provides a contact pin holder, capable of being relatively easily sophisticated, while keeping desired characteristic impedance of a transmission line of the contact pin holder.

In order to achieve the object of the invention described above, the present invention provides a contact pin holder adapted to contact a plurality of terminals of an electronic device to corresponding contacts of a circuit board, comprising: an insulative substrate; a conductive member disposed on an inner surface of each of a plurality of holes disposed in the substrate; and a plurality of conductive contact pins, each inserted into and held in a respective hole of the plurality of holes so that each contact pin is electrically insulated from a corresponding conductive member, wherein at least one contact pin and the conductive member of the hole into which the at least one contact pin is inserted cooperatively define a coaxial transmission line.

In a contact pin holder according to the present invention, by constituting a substrate using insulative material, the weight of the contact pin holder may be reduced. The contact pin holder may be easily sophisticated, for example, a plurality of ground systems may be easily provided in the contact pin holder. Further, the possibility of design of the contact pin holder may be improved, for example, when a conductive material is disposed on an inner surface of a hole into which a contact pin is inserted, the conductive material may be partially disposed on the inner surface of the hole. Brief Description of the Drawings

Fig. 1 is a perspective view of a contact pin holder provided with a guide, according to the present invention.

Fig. 2 is a perspective view of the contact pin holder of Fig. 1.

Fig. 3 is a perspective view of a modification of the contact pin holder of Fig. 2.

Fig. 4 is a cross-sectional view of a contact pin holder according to a first embodiment.

Fig. 5 is a view showing a structural example of a contact pin of Fig. 1.

Fig. 6 is a cross-sectional view of a contact pin holder according to a second embodiment.

Fig. 7 is a cross-sectional view of a contact pin holder according to a third embodiment.

Detailed Description

Fig. 1 is a perspective view of a contact pin holder with a guide 1 according to one embodiment of the present invention. Contact pin holder with guide 1 has a contact pin holder (hereinafter, referred to a holder) 2, a plurality of conductive contact pins 3 held by holder 2, and a guide body 4 which supports holder 2. Guide body 4 has a guide part or a guide surface 41 for locating an electronic device to be tested (not shown) at a

predetermined position on holder 2. Guide body 4 further has a positioning part (a positioning hole 42 as shown in Fig. 1) for locating holder 1 at a predetermined position of a testing device (not shown) which tests the electronic device. Guide body 4 may have a positioning pin or a notch, instead of positioning hole 42.

Fig. 2 is a perspective view of holder 2 of Fig. 1. Holder 2 has a substrate 21 like a plate or a layer, made from insulative material such as glass epoxy. Each contact pin 3 is held by (for example, pressed into) substrate 2 so as to extend generally perpendicular to a surface 22 of substrate 21. In the example of Fig. 2, holder 2 is constituted by two platelike substrates 21 connected to each other by means of a connecting means such as a bolt 5 and a nut 6. Between the two substrates, a conductive layer (connecting part), as described below, is dispose. Holder 2 may have a positioning pin 7 which engages a positioning hole (not shown) formed on guide body 4. In addition, holder 2 may be formed by a substantially integral substrate, or may be dividable so as to facilitate assembling contact pins 3, as described below.

Fig. 3 is a perspective view of a modification of holder 2 of Fig. 2. In this modification, a surface of substrate 21 is not a substantially one plane, and has a plurality of (two in the embodiment) planes 22, 23 formed by a step or the like. As such, the holder may have the suitable configuration depending on the shape of the contact pin and/or the electronic device to be tested.

Fig. 4 is a cross-sectional view of holder 2 of the first embodiment as shown in Fig. 2, indicating a cross-section parallel to the extending direction of the contact pin. Holder 2 has insulative substrate 21 and a plurality of (four in the embodiment) contact pins 3a - 3d inserted into and held by substrate 21. In this embodiment, contact pins 3 a and 3 c are explained as ground pins, and contact pins 3b and 3d are explained as signal pins.

Fig. 5 shows an example of the concrete structure of each contact pin. Contact pin 3 a has a generally cylindrical hollow shell 31 inserted into a hole for pin (as described below) formed on holder 2, an elastic member 32 (coil spring in the example) disposed within shell 31 and capable of expanding or contracting in an axial direction of shell 31, a first conductive plunger 33 positioned at one end (the lower end in the embodiment) of coil spring 32 and projecting from one end (the lower end in the embodiment) of shell 31 so as to electrically contact a testing device (not shown), and a second conductive plunger 34 positioned at the other end (the upper end in the embodiment) of coil spring 32 and projecting from the other end (the upper end in the embodiment) of shell 31 so as to electrically contact an electronic device (not shown). Each of first and second plungers 33 and 34 contacts shell 31 , and thus a conductive path may be defined extending from first plunger 33 to second plunger 34 via shell 31. Alternatively or additionally, coil spring 32 may be made from conductive material, so that another conductive path extending from first plunger 33 to second plunger 34 via coil spring 32. Although Fig. 5 shows contact pin 3a, contact pins 3b - 3d may have the same structure as contact pin 3a.

Each contact pin extends generally perpendicular to surface 22 of holder 2 and passes through holder 2. In detail, contact pins 3 a, 3 c is held by press fitting, in a first hole for pin 24 formed in substrate 21 constituting holder 2, and a conductive material 241, such as copper, silver or gold, is provided on an inner surface of each hole for pin 24 by plating or the like. Therefore, contact pins 3a, 3c are at least partially electrically connected to conductive material 241. On the other hand, contact pins 3b, 3d is held by press fitting, in a second hole for pin 25 formed in substrate 21 constituting holder 2. In the exemplary embodiment, shell 31 of each contact pin is held by plate-like substrates 27, 28 each having a hole with a diameter smaller than an outer diameter of shell 31. Also, a conductive material 251 , such as copper, silver or gold, is provided on an inner surface of each hole for pin 25 by plating or the like. A diameter of second hole for pin 25 is larger than a diameter of first hole for pin 24. Therefore, each of contact pins 3b, 3d does not contact conductive material 251 (or contact pin 3b, 3d are insulated from conductive material 251), whereby each of contact pins 3b, 3d and conductive material 251 cooperatively constitute a coaxial transmission line. In this regard, the term "coaxial transmission line" means the configuration wherein shell 31 of the contact pin is insulated from conductive material 251 , and shell 31 is covered (or electromagnetically shielded) by the conductive material. In other words, "coaxial transmission line" does not mean only the case wherein the contact pin and the conductive material have cylindrical shapes which have the same axis. For example, the outer surface of the contact pin and the inner surface of the conductive material may have cylindrical shapes which are eccentric to each other.

In contact pins 3b, 3d, a dielectric material 35, such as resin or ceramics, may be disposed or filled between the outer surface of shell 31 and the inner surface of conductive material 251. Otherwise, without disposing the dielectric material between the outer surface of shell 31 and the inner surface of conductive material 251 , an area between them may be gas-phase, such as air, nitrogen or oxygen, or vacuum-phase.

The coaxial transmission line is constituted so as to have predetermined characteristic impedance. For example, when shell 31 of contact pin 3b or 3d has the cylindrical shape with an outer diameter "d" and conductive material 251 has the cylindrical shape with an inner diameter "D," and the cylinders are coaxial, characteristic impedance Zo of the coaxial transmission line may be calculated by a following equation. In the equation, "ε" is the permittivity of the material (the dielectric material or the gas- phase in the embodiment) between the contact pin and the conductive material. By properly determining the parameters "d," "D" and "ε," desired characteristic impedance may be obtained in each signal pin. Zo = 60/ε ¹ " · ln(D/d)

As shown in Fig. 4, holder 2 has a connecting part 26, which is stacked on or embedded in substrate 21, adapted to electrically connect conductive material 241 to conductive material 251. In the embodiment of Fig. 4, connecting part 26 is a conductive layer stacked between two plate-like substrates 21. By electrically connecting conductive material 241 to conductive material 251 by means of connecting part 26, each of contact pins 3a, 3c, inserted into hole 24, may be electrically connected to conductive layer 26 via conductive material 241.

Holder 2 may be formed as a substantial unified unit, otherwise, may be formed by combining some components in view of assembling of the contact pins or positioning the connecting part. For example, in the embodiment of Fig. 4, in order to dispose conductive layer 26 within the holder, substrate 21 is constituted by stacking a plurality of (two in the embodiment) layers and disposing connecting part (conductive layer in the embodiment) 26 between the layers. Further, in order to facilitate forming the conductive material (for example, a conductive coating) on the inner surface of the hole for pin, plate-like substrates 27, 28 may be bonded to substrate 21 after forming the conductive material on the inner surface of the hole for pin.

Fig. 6 is a cross-sectional view of a holder 2' used in a contact pin holder according to a second embodiment of the invention. Holder 2' has first and second connecting parts 26a', 26b', whereby the holder may have two ground systems. Concretely, first connecting part 26a' electrically connects a conductive material 241a', formed on an inner surface of a hole for pin 24a' into which a contact pin 3 a' is inserted, to a conductive material 241b', formed on an inner surface of a hole for pin 24b' into which a contact pin 3b' is inserted. Similarly, second connecting part 26b' electrically connects a conductive material 241c', formed on an inner surface of a hole for pin 24c' into which a contact pin 3 c' is inserted, to a conductive material 24 Id', formed on an inner surface of a hole for pin 24d' into which a contact pin 3d' is inserted. Further, first and second connecting parts 26a'and 26b' are insulated from each other. The contact pin holder may have three or more connecting parts, so as to configure three or more ground systems. In the second embodiment, each connecting part may be constituted as a conductive layer. In the second embodiment, contact pins 3a', 3c' are explained as ground pins, and contact pins 3b', 3d' are explained as signal pins.

In the second embodiment, substrate 2Γ of holder 2' is made from dielectric material, not conductive material such as metal, and thus a plurality of ground systems may be easily disposed in the substrate. When the contact pin holder has a plurality of ground systems, even when different signals, such as analogue and digital signals, high and low frequency signals or high and low amplitude signals, should be transmitted through the contact pin holder, an independent ground system suitable for each of the different signals may be configured, whereby the signal passing through the transmission line may be stable.

Fig. 7 is a cross-sectional view of a holder 2" used in a contact pin holder according to a third embodiment of the invention. Holder 2" may have at least one (two in the embodiment) dielectric layer 211", 212" stacked on (preferably, embedded in) substrate 21" made from insulative material such as glass epoxy. Conductive layers 213", 214" are formed on both sides of conductive layer 211", and conductive layers 215 ", 215 " are provided on both sides of conductive layer 212". Therefore, each conductive layer and the conductive layers on the both sides thereof cooperatively constitute a capacitor. In other words, holder 2" is constituted by stacking the insulative material or the substrate, the conductive layers and the dielectric layer. In order to increase a capacity of the capacitor, it is preferable that a dielectric constant of each dielectric layer is high as possible. Further, it is preferable that each dielectric layer is a high dielectric member having the higher dielectric constant than that of substrate 21". As the high dielectric material, an

"Embedded Capacitor Material (ECM)", available from 3M Company, may be used. The ECM is provided as a flexible sheet from the high-dielectric material. Such a holder may be made by a method of making a printed-circuit board.

The dielectric layer may include polymer. Preferably, the dielectric layer includes polymer and a plurality of particles. Concretely, the dielectric layer may be made by mixing resin and particles. Preferable resin may include epoxy, polyimide, polyvinylidene- fluoride, cyanoethyl pullulan, benzocyclobutene, polynorbornene, polytetrafluoro-ethylene, acrylate, and the mixture thereof. The particles may include dielectric (insulating) particles, for example, barium titanate, barium titanate strontium, oxidized titanium, lead titanate zirconium, and the mixture thereof.

For example, the thickness of each dielectric layer may be equal to or larger than

0.5μιη. The thickness of each dielectric layer may be equal to or smaller than 20μιη. The smaller the thickness, the larger is the electrostatic capacity of the capacitor. For example, the thickness may be equal to or smaller than 15μιη, or ΙΟμιη. On the other hand, the larger the thickness, the stronger is the adhesive strength. For example, the thickness may be equal to or larger than 1 μιη.

It is preferable that the relative permittivity of the dielectric layer is high as possible. For example, the relative permittivity may be equal to or larger than 10 or 12.

Although there is no upper limit of the relative permittivity, the relative permittivity may be equal to or smaller than 30, 20 or 16.

When the high-dielectric material is used as the dielectric layer, the distance between the neighboring capacitors may be advantageously reduced. When two capacitors are positioned close to each other, the electrostatic capacitance may also be obtained between a ground layer of one capacitor and a ground layer of another neighboring capacitor. In the case that the high-dielectric material is used between the conductive layers, by which the electrostatic capacitance should be obtained, even when the distance between the conductive layers of one capacitor and the distance between two neighboring capacitors are equal to each other, the electrostatic capacitance of each capacitor may be increased. Therefore, the distance between the neighboring capacitors may be relatively small, whereby the thickness of the holder may be reduced.

The conductive layers formed on the both sides of each high-dielectric layer constitute ground layers electrically connected to the ground pin. In detail, conductive layer 213" on the upper side of first high-dielectric material 211", close to an electronic device-side surface (a top surface in Fig. 7) 271" of holder 2, and conductive layer 214" on the lower side of first high-dielectric material 211" may function as a ground layer.

Similarly, conductive layer 215" on the upper side of first high-dielectric material 212", close to a testing device-side surface (a bottom surface in Fig. 7) 281" of holder 2, and conductive layer 216" on the lower side of first high-dielectric material 212" may function as a ground layer. In other words, in the embodiment of Fig. 7, contact pins 3a", 3c" connected to ground layers 214", 215" and contact pin 3sd" connected to ground layers 213", 216" may function as the ground pins. Further, contact pin 3b" of the coaxial transmission line, which is not connected to either of the layers, functions as the signal pin.

Each high-dielectric layer and the conductive layers on the both sides thereof may be provided on whole area of holder 2. Therefore, an area of the capacitor thus formed may be generally the same as that of holder 2.

As shown in Fig. 7, it is preferable that the capacitor within holder 2", having the high-dielectric layer sandwiched by the ground layers, is positioned as close as possible to top surface 271" or bottom surface 281" of holder 2". This is because, the smaller the distance between the surface of holder 2" and the conductive layer is, the signal transmission property may be more improved during testing the electronic device.

Concretely, the smaller the distance between top surface 271" of holder 2" and high- dielectric layer 211" is, the input sensitivity of the electronic device to be tested is more improved, and the smaller the distance between bottom surface 281" of holder 2" and high- dielectric layer 24 or 25 is, the output sensitivity of the electronic device to be tested is more improved. In the present invention, the holder, including the high-dielectric layer sandwiched by the ground layers, is substantially unified, thus the capacitor may be easily positioned close to the surface of the holder, whereby the test of the electronic device can be carried out with a high degree of accuracy.

Another embodiment, including two or more features in the three embodiments as explained above, may be possible. For example, connecting part 26 of the first

embodiment may be applied to the second embodiment of Fig. 6, and two or more connecting parts may be used as in the third embodiment of Fig. 7. Further, each embodiment may include one or more power source pin.

The material constituting holder 2, 2' or 2" may include paper instead of glass fiber, and may include phenol resin or polyamide resin instead of epoxy resin. As the material constituting the conductive layer, silver or gold may be used instead of copper.

In the present invention, the holder is formed by insulative material and at least one signal pin constitutes the coaxial transmission line having predetermined characteristic impedance. Therefore, in comparison with a holder formed by conductive material such as metal, the holder is relatively light and sophisticated while having the predetermined characteristic impedance. For example, the holder may have a plurality of ground systems by means of a plurality of connecting parts, and/or may have a capacitor by means of a dielectric layer and conductive layers on the both sides of the dielectric layer. Further, the possibility of design of the holder may be improved, for example, when a conductive material is disposed on an inner surface of a hole into which a contact pin is inserted, the conductive material may be partially disposed on the inner surface of the hole.

In the above embodiments, each contact pin extends through the holder. However, at least one contact pin may partially extend (or terminate) in the holder in the thickness direction of the holder. In this case, the contact pin which terminates in the holder and another contact pin may be electrically connected by a connecting means similar to connecting part 26 as described above. Due to this, a pitch or array of contact pins on the top surface of the holder may be different from that on the bottom surface of the holder.

Reference Signs List

1 contact pin holder with guide

2 contact pin holder

21 substrate

24, 25 hole for pin

26, 26a', 26b' connecting part

211", 212" dielectric layer

213", 214", 215", 216" conductive layer

3a, 3b, 3c, 3d contact pin

31 shell

32 coil spring

33 first plunger

34 second plunger