DE102010011854B4 - Measuring head for improved contacting - Google Patents

Abstract

Measuring head (M)
- With a base body (G) having on a top (O) a central region (ZB) and a peripheral region surrounding the central region (RB),
- Having a contact spring (KF) having a support area (AB), with which it rests on the edge region (RB) of the base body (G), and a contact area (KB),
- With a recess (A) through the base body (G) in the central region (ZB),
- With a second contact spring (KF2), wherein
the contact region (KB) of the contact spring (KF) is arranged at a distance above the upper side (O),
- The second contact spring (KF2) has a second support area (AB) with which it rests on an edge region (RB) on an underside of the base body (G),
- The second contact spring (KF2) has a second contact region (KB) which projects through the recess (A) in the central region (ZB) and is arranged at a distance above the top (O).

Description

The invention relates to measuring heads for improved contacting of z. B. to be tested electrical or electronic components.

In the development and production of electrical or electronic components, eg. As RF devices, an inspection of the components for compliance with specification is essential. A test can already be advantageous in the form of on-wafer measurements during the manufacturing process. In particular, during the final inspection of a finished component, all functions provided by the component are to be tested in order to avoid the delivery of defective components. The inevitable consequence of this is that every single part of a batch has to be tested.

In order to do this with great reliability and low costs, the following minimum requirements for a measuring system arise: Reliable contacting should also be possible with lightly soiled or oxidized contacts. Each individual measurement should be able to be carried out as quickly as possible. This means for a corresponding measuring head that the measuring head should be able to be aligned in a short time relative to the corresponding component and that the contacting is advantageously carried out by a contact between a measuring head and the device under test (DUT = Device Under Test). Furthermore, a large number of measurements must be carried out before signs of wear, which necessitate the maintenance and repair of a corresponding measuring head, occur.

From the patent US 7,053,640 B2 is a test environment for RF circuits known that allows high isolation. However, the described test environment is only suitable for measurements of components that have already been separated after the manufacturing process. An "on-wafer measurement", ie the measurement of planar adjacent components, which were produced together on a wafer and which are not yet isolated, is not possible with this test environment.

From the publication WO 2007/146584 A2 Contacting devices with spring structures are known. Their spring structures are complicated to manufacture and prone due to the composite structure; Bending or breaking a test spring will cause the entire probe to become inoperative because it can no longer be guaranteed that every single component function can be tested.

Another desirable feature of measuring heads is the lowest possible electromagnetic coupling of the spring elements that make contact with the device under test. The measuring heads of the publications listed above have a relatively high electromagnetic coupling of the spring elements.

From the DE 697 33 928 T2 For example, microelectrical contact structures having elongate spring contact elements connected to a base plate in a support area are known.

From the DE 697 27 945 T2 For example, devices for contacting and testing semiconductor devices are known. Kontaktierungsschuhe are arranged on a base body with a breakthrough or an upwardly opening cavity.

From the DE 10 2004 051 384 A1 For example, devices for producing symmetrical high-frequency circuits are known. A DUT (Device Under Test) can be connected via cable to a vector network analyzer.

It is therefore an object of the present invention to provide a measuring head, which allows a quick and reliable contact and has a low wear. Another object is to provide a probe with spring elements that enables on-wafer measurements. Another object is to provide a measuring head which allows electromagnetically decoupled spring elements.

These objects are achieved by a measuring head according to claim 1. Advantageous embodiments emerge from the subclaims.

The invention comprises a measuring head with a main body and a contact spring. The main body has a central area on an upper side and an edge area that at least partially encloses the central area. The contact spring has a support region, with which it rests on the edge region of the base body, and a contact region. The contact region is arranged at a distance above the upper side of the main body.

In this case, the contact region of the contact spring can produce a galvanic connection between the measuring head and the component to be tested when a connection pad of a component to be tested is touched. The contact spring can be interconnected via electrical lines with a test system. This produces a reliable galvanic connection between the device under test and the test environment.

If the contact spring or its contact region and a connection pad of a component are pressed against one another, the grinding or scratching of the contact region of the contact spring on the potentially soiled or oxidized surface of a contact pad of the component causes the contamination or the oxide layer to penetrate when the contact spring is compressed and bent. so that nevertheless a reliable contact can be made.

Because only a pressing against one another is necessary for producing a galvanic contact between the measuring head and the component, the measuring head and the component to be tested can be quickly brought into position relative to each other. The measurement is therefore not delayed by a lengthy and complicated alignment of the measuring head or the component; the measurement can be done quickly.

The arranged on the top of the body contact spring is simple; It is preferably well connected to the body and does not require a complicated structure. Such a contact spring can be a single metal layer with an upturned end. In this case, the upwardly bent end of the contact region of the contact spring. Inventive contact springs with a contact area and a support area are simple and therefore work with great reliability and small risk of failure.

The contact spring may be soldered to the top of the body. The contact between the contact region of the contact spring and the connection pad of the component can be effected by touching a tip or an upper edge of the contact spring in the contact region with the component. A contact area, which serves for the supply or discharge of electrical signals, is a signal-carrying contact area and may be e.g. be designed strip-shaped and narrow to keep a capacitive crosstalk small.

If a contact spring of the measuring head makes contact with a ground connection pad of a component, it is referred to as a "ground contact spring". These ground contact springs are preferably wide and as short as possible to avoid larger parasitic contact inductances. Their distance from the signal-carrying contact springs is kept as small as possible. The distance is preferably less than 150 microns.

The contact area and the support area may be substantially the same width.

It is also possible for the contact area to be wider, e.g. 1.2 times as wide, 1.5 times as wide, 1.75 times as wide, twice as wide, or three times as wide as the overlay area.

But it is also possible that the support area wider, z. B. 1.2 times as wide, 1.5 times as wide, 1.75 times as wide, twice as wide or three times as wide as the contact area. If the contact area is narrower than the support area, the risk of inadvertently touching the contact areas of different springs in the "narrowness" of the central area is reduced.

The contact springs may taper from the support region to the contact region and may be e.g. Trapezoidal be formed.

In one embodiment, the contact spring between the support area and the contact area comprises a bending edge. The bending edge connects the horizontally arranged on the body support area with the upwardly bent contact area of the contact spring. Metals are well suited as a material of the contact spring, since they are electrically conductive and on the one hand can be plastically deformed so that the contact area is always bent upwards, and on the other hand, the deformation by lightly pressing the contact spring to a component or the component to the contact spring represents an elastic, often repeatable deformation of the contact area.

In one embodiment, the measuring head comprises a recess through the base body in the central region. The bending edge of a contact spring or the bending edges of one or more arranged on the body contact springs may be aligned along the edge of the recess. The recess is preferably polygonal. That is, their edge region has rectilinear portions on the surface of the main body. These rectilinear regions preferably coincide with the bending edges of the contact springs.

In one embodiment, the recess is made rectangular by the main body. Alternatively, triangular, pentagonal, hexagonal and octagonal recesses come into question.

In one embodiment, the measuring head comprises a second contact spring. The support region of the second contact spring rests on an edge region on the underside of the base body. The contact region of the second contact spring protrudes through a recess in the central region, so that the contact region is arranged at a distance above the upper side of the main body. In other words, the measuring head comprises two levels, from which contact springs extend with their contact areas upwards. This is the result Possibility to contact pads on a device to be tested, significantly improved. Such a measuring head therefore has more degrees of freedom for arranging the contact springs than known contacting devices.

In one embodiment, the measuring head comprises a third spring, namely a shielding spring, with a third support area and a shielding area. The third bearing area is arranged on the edge area of the upper side or on the edge area of the lower side of the base body. The shielding region of the shielding spring is arranged relative to the first contact spring under its first contact region or relative to the second contact spring via its second contact region. The shielding area is galvanically isolated from the contact area of the contact spring. Such a shielding spring as part of the measuring head is well suited to isolate signal-carrying contact springs; an (unwanted) electromagnetic coupling signal-carrying contact springs is thus significantly reduced. The shielding spring can be connected to ground. It can be interconnected with the mass of a test device. It can touch a ground contact pad of the device under test. It can touch a contact pad of the DUT. But their shielding can also be provided only for shielding, touching a contact pad but without contact to protrude upwards.

In one embodiment, the measuring head comprises an auxiliary spring with a fourth support area and an auxiliary contact area. The fourth bearing area is arranged on the edge area of the upper side or on the edge area of the underside of the main body. The auxiliary contact region is arranged relative to the first contact spring under its (first) contact region and presses from below against the first contact region. Such an auxiliary spring can fulfill two tasks. On the one hand, it can increase the mechanical contact force between the contact region and a connection pad of the component. On the other hand, it can reduce the ohmic resistance of the contact because it represents a parallel circuit and thus an alternative path for electrical signals.

In one embodiment, the measuring head has a contact spring arranged on its upper side with a recess in the contact region. Through the recess in the contact region protrudes disposed on the underside second contact spring. It is advantageous that the upper contact spring can be made wide and thereby allows a high contact pressure without blocking lower contact springs by a large area.

In one embodiment, the measuring head comprises two springs whose bearing areas are arranged side by side on the edge region of the top or bottom, but whose contact areas are arranged vertically one above the other. The contact areas do not touch each other when they are elastically deformed by pressing against an electrical component or module. One of the two contact springs can be a shielding spring.

In one embodiment, a contact spring is connected to ground. In an embodiment, the base body comprises a printed circuit board. At least one or more or all of the contact springs comprise a material selected from copper, beryllium, tungsten, gold and silver. In particular, copper alloys, beryllium alloys and tungsten alloys are suitable as spring materials since they have good elasticity and good electrical conductivity. In one embodiment, the contact springs of the measuring head have a length between 0.5 and 5 mm, a thickness between 50 and 150 μm and a width between 100 and 500 μm. The main body of the measuring head can be round and have a diameter between 35 and 55 mm. The main body can be a PCB (Printed Circuit Board) with e.g. 45mm diameter.

In one embodiment, the measuring head comprises a recess, for. B. a polygonal recess, in the central region through the body. A contact spring is arranged with its support area on the underside of the base body. Their contact area protrudes into the recess and encloses an angle α with the underside of the main body or of the upper side of the main body, wherein 15 ° ≤ α ≤ 75 °. It is also possible for α to hold: 15 ° ≦ α S 25 ° or 25 ° ≦ α ≦ 30 ° or 30 ° ≦ α ≦ 45 ° or 45 ° ≦ α ≦ 75 °.

In one embodiment, the stroke of the contact region is between 25 and 100 μm. The stroke corresponds to the difference between the distances between the component and the measuring body and on the one hand in the relaxed, d. H. not elastically bent, state and on the other hand in the state of contact provided for pressing against the device. In other words, the stroke corresponds to the contact pressure when contacting.

In one embodiment, the probe is connected via coaxial lines to a multiturn network analyzer of the test environment.

In one embodiment, a contact region of a contact spring presses against a terminal pad of an electrical device to be tested, thereby interconnecting a multiturn network analyzer to the device.

In an embodiment, the probe comprises a reference potential body. This one can Be body with an electrically conductive surface. It can be arranged below the contact areas of all or individual contact springs. The reference potential body can be connected to the reference potential of the measuring head, for. B. with ground, be connected. Such a reference potential body can reduce or prevent the unwanted coupling of different contact springs.

• 1 eine Ausführungsform mit einer Kontaktfeder auf einem Grundkörper,
• 2 einen Grundkörper mit Ausnehmung und zwei Kontaktfedern,
• 3 einen Grundkörper mit Kontaktfedern auf seiner Ober- und seiner Unterseite,
• 4A das Profil einer Kontaktfeder,
• 4B das Profil einer Kontaktfeder mit einer Biegung im Kontaktbereich,
• 4C das Profil einer Kontaktfeder mit zwei Biegekanten im Kontaktbereich,
• 4D das Profil einer Kontaktfeder mit einer Biegekante im Kontaktbereich,
• 5 eine Anordnung verschieden geformter Kontaktfedern auf einem Grundkörper,
• 6 verschiedene Kontaktfedern mit verschieden geformten Auflagebereichen und Kontaktbereichen,
• 7 verschiedene Kontaktfedern mit verschieden geformten Auflagebereichen und Kontaktbereichen,
• 8A eine Ansicht eines Messkopfes mit einem Bezugspotenzial-Körper,
• 8B eine Ansicht eines Messkopfes mit einem Bezugspotenzial-Körper,
• 8C eine Ansicht eines Messkopfes mit einem Bezugspotenzial-Körper,
• 8D eine Ansicht eines Messkopfes mit einem Bezugspotenzial-Körper,
• 8E eine Ansicht eines Messkopfes mit einem Bezugspotenzial-Körper,
• 8F eine Ansicht eines Messkopfes mit einem Bezugspotenzial-Körper,
• 8G eine Ansicht eines Messkopfes mit einem Bezugspotenzial-Körper,

The measuring head will be explained in more detail below on the basis of exemplary embodiments and associated schematic figures. Show it:

• 1 an embodiment with a contact spring on a base body,
• 2 a basic body with a recess and two contact springs,
• 3 a body with contact springs on its top and bottom,
• 4A the profile of a contact spring,
• 4B the profile of a contact spring with a bend in the contact area,
• 4C the profile of a contact spring with two bending edges in the contact area,
• 4D the profile of a contact spring with a bending edge in the contact area,
• 5 an arrangement of differently shaped contact springs on a base body,
• 6 various contact springs with differently shaped contact areas and contact areas,
• 7 various contact springs with differently shaped contact areas and contact areas,
• 8A a view of a measuring head with a reference potential body,
• 8B a view of a measuring head with a reference potential body,
• 8C a view of a measuring head with a reference potential body,
• 8D a view of a measuring head with a reference potential body,
• 8E a view of a measuring head with a reference potential body,
• 8F a view of a measuring head with a reference potential body,
• 8G a view of a measuring head with a reference potential body,

1 shows the arrangement of a contact spring KF on a base body G a measuring head M , The main body G includes a central area For example, and a border area RB , The contact spring KF includes a support area FROM with which they are on the edge area RB of the basic body G is arranged. The contact area KB the contact spring KF protrudes at an angle α relative to the top O of the basic body G up. This is the contact area KB at a distance above the top O arranged. The measuring head M and the DUT to be measured are pressed against each other in the case of a test of a device under test (not shown here) so that the contact area KB the contact spring KF presses against a terminal pad of the device and thus an electrical interconnection between the device and the measuring head M is made.

2 shows a main body G with a recess A in the central area For example, through the main body G , On the top of the edge region is a contact spring KF arranged. Left at the bottom of the edge area is another contact spring KF2 arranged. The contact area KB the left contact spring KF2 is trapezoidal. He tapers from the bending edge BK towards the end of the contact area.

3 shows a cross section through a measuring head M and a component arranged above it BE , The main body G includes contact springs on both its top and bottom. The contact area KB one of the lower contact springs contacts the device BE , The second spring HIF represents an auxiliary spring, whose auxiliary area HIB from below against the contact area KB one of the upper contact springs presses.

4A illustrates a basic form of a contact spring KF with a support area FROM , a contact area KB and a bending edge BK that the contact area KB with the support area FROM combines.

4B shows an embodiment of a contact spring KF who are in their contact area KB a second bending edge BK2 having. In the case of contacting with a connection pad of a component touches the bending edge BK2 the connection pad.

4C shows an embodiment of a contact spring KF with two bending edges BK2 . BK3 in the contact area KB , The bends between the segments of the contact region can be designed so that in the case of contacting, ie, upon deformation of the contact region, the contact region flat with a contact surface KFL is connected to a connection pad of a device.

The embodiments of 4B and 4C differ in that the contact of the spring of 4C can be made flat with a connection pad. In contrast to touches the contact spring of 4B a connection pad essentially with its bending edge. Then, with the same contact force, the contact area is reduced and increases the contact pressure.

4D shows a further embodiment of a contact spring, wherein the contact region has a bend or a bending edge. The terminal part of the contact spring is bent more steeply upwards than the part of the contact spring connected to the contact area.

5 shows possible shapes of the contact area, the sake of simplification on the same body G are shown. A first contact area KBA extends in a first portion having a first width, which may correspond to the width of the contact spring in the support area. In a second section, the width of the contact area is reduced.

The second contact area KBB includes a recess AU. Through this recess, for example, a contact region of a arranged on the underside of the body contact spring project upwards.

The contact areas KBC and KBD belong to contact springs whose bearing areas next to each other on the edge area RB of the basic body G of the measuring head M are arranged. Here is the spring with the contact area KBC on the top and the spring with the contact area KBD on the bottom of the main body G arranged. But the contact springs can also both be arranged side by side on the top or on the underside of the base body. Their shape makes it possible, for. B. at different bending angles that the contact areas KBC and KBD overlap. For example, the contact area KBD represent a shielding area of a shielding spring, which is the contact area KBC Electromagnetically decoupled from the contact areas of other contact springs.

6 shows further possible embodiments of the contact springs KF , for simplicity's sake, on the same basic body G are shown. The contact springs may have contact areas, which taper or widen from the bending edge towards the point provided for contacting. Contact areas may have more than one intended for contacting site or recesses. The width of the contact spring may have a crack at the bending edge and be wider or narrower. The contact area may include areas in which the width is constant and areas in which the width varies. In particular, the shape of the contact springs can be designed so that an electromagnetic coupling between different springs is minimized.

7 shows further possible embodiments of the contact springs KF , which are shown for reasons of simplification on the same body. Exemplary are three side by side arranged contact springs KF denoted by reference symbol "KF". The contact springs may be arranged in groups, wherein the contact springs of a group have a smaller distance from one another than to contact springs of other groups.

8A shows a cross section through a measuring head M , The measuring head M further includes a reference potential body BPK , This may comprise a body with an electrically conductive surface and be arranged below the contact areas. The reference potential body may be solidly formed of a metal. It can include an alloy. It may be truncated pyramidal and may include gold. The reference potential body BPK can with the reference potential of the measuring head, z. B. with ground, be connected. It is arranged as close as possible to the contact regions of the contact springs, but preferably without touching them during the measurement. The reference potential body BPK can be spaced by different width column of the springs. Then the reference potential body acts BPK as a reference potential for electrical signals that propagate in the contact springs. The reference potential body BPK can significantly improve the impedance matching in propagating RF signals in this way.

8B shows a cross section through a measuring head M with a reference potential body BPK , where the main body G of the measuring head M Has arranged on the top and on the underside of the body arranged contact springs. The contact areas KB the contact springs contact the device BE ,

8C shows a cross section through a measuring head M with a reference potential body BPK wherein the reference potential body has a plurality of grooves NU includes, whose gradients are adapted to the course of the contact areas of the contact springs. A groove NU can do a wall W or two walls W include. A groove can also be open to one side and exactly one wall W include. In 8C are the sidewalls of the grooves NU shown. A contact region may then be disposed in a groove without touching the reference potential body. Thus, the contact area is better protected not only downwards but also laterally against couplings with contact areas of other contact springs. The reference potential body may be completely or partially coated with a dielectric. A dielectric may be disposed locally on the reference potential body to prevent accidental contact of a contact area.

8D shows a cross section through a measuring head M with a groove NU in a reference potential body BPK , The contact area of a lower contact spring KF runs to a large extent in the groove NU in the reference potential body BPK , Between the contact spring with the contact area KF whose support area is arranged on the underside of the base body, and the reference potential body is provided a cutout. The contact area of the contact spring does not touch the reference potential body. The contact region of an upper contact spring extends to a smaller extent in the groove NU in the reference potential body BPK ,

8E shows a cross section through a measuring head M with a reference potential body BPK , At the reference potential body BPK is another spring F, which is the device BE contacted, arranged.

8F shows a cross section through a measuring head M with a reference potential body BPK , In the reference potential body BPK are openings PP for receiving spring-loaded contact pins KS arranged. A contact pin KS contacts the device BE , Another contact pin KS contacts the contact area of a contact spring electrically or mechanically supports it.

A contact pin may be a commercially available spring-loaded contact pin.

8G shows a cross section through a measuring head M with a reference potential body BPK , The reference potential body BPK includes massive peaks MS on its upper side, which makes electrical or mechanical contact with a component BE produce. The direct placement of the device on the reference potential body can be controlled by mechanical or electrical mechanisms. In particular, the contact pressure can be electrically or mechanically controlled, regulated or limited.

The use of a spring-loaded contact pin in a measuring head according to the invention is not dependent on the presence of reference potential bodies.

A measuring head is not limited to one of the embodiments described or illustrated. Variations, which z. B. even more contact springs in other positions, z. B. third or fourth layers, a multilayer main body, further form variants of contact areas or support areas, further recesses in the body or any combinations thereof include, represent embodiments of the invention also represent. In particular, also provide measuring heads with deviating shaped contact springs embodiments of the invention.

LIST OF REFERENCE NUMBERS

A:

recess

FROM:

support area

AF:

Abschirmfeder

BE:

electrical or electronic component

BK,

BK1 . BK2 : Bending edge

BPK:

Reference potential body

G:

body

HIB:

auxiliary area

HIF:

auxiliary spring

KB, KBA, KBB, KBC, KBD:

contact area

KF, KF2:

contact spring

KFL:

contact area

KS:

pin

M:

probe

MS:

massive top

NU:

groove

O:

top

PP:

Opening for receiving a spring-loaded contact pin

RB:

border area

W:

Wall of a groove

For example:

central area

Claims (15)

Measuring head (M) - with a base body (G) having on a top (O) a central region (ZB) and a peripheral region surrounding the central region (RB), - with a contact spring (KF), a support area (AB ), with which it rests on the edge region (RB) of the base body (G), and has a contact area (KB), - with a recess (A) through the base body (G) in the central region (ZB), - with a second contact spring (KF2), wherein - the contact region (KB) of the contact spring (KF) at a distance above the top (O) is, - the second contact spring (KF2) has a second bearing region (AB), with which it rests on an edge region (RB) on an underside of the base body (G), - the second contact spring (KF2) has a second contact region (KB) which projects through the recess (A) in the central region (ZB) and is arranged at a distance above the upper side (O). Measuring head according to the preceding claim, wherein the contact spring (KF) between the support area (AB) and the contact area (KB) comprises a bending edge (BK). Measuring head according to one of the preceding claims with a polygonal recess (A) through the base body (G) in the central region (ZB). Measuring head according to the preceding claim with a rectangular recess (A) through the main body (GK) in the central region (ZB). Measuring head according to one of the preceding claims, comprising - A shielding spring with a third support area and a shielding area (KBD), wherein - The third bearing area on the edge region (RB) of the top (O) or on the edge region (RB) of the underside of the base body (G) is arranged and - The shielding (KBD) of the shielding spring under the first contact region (KBC) of the contact spring or over the second contact region of the second contact spring is arranged and is electrically isolated from the contact region (KBC). Measuring head according to one of the preceding claims, comprising - An auxiliary spring (HIF) with a fourth support area and an auxiliary area (HIB), wherein the fourth bearing area is arranged on the edge area (RB) of the upper side or the lower side of the main body (G), - The auxiliary area (HIB) is located below the first contact area (KB) and presses against the first contact area (KB). Measuring head according to one of the preceding claims, having a first contact spring (KF) arranged on the upper side (O), whose contact region (KBB) has a recess (AU) through which the contact region of a second contact spring arranged on the underside protrudes. Measuring head according to one of the preceding claims, with two contact springs, whose contact areas are arranged side by side on the edge region (RB) of the upper side (O) or the underside, the contact areas (KBC, KBD) are arranged vertically one above the other and their contact areas (KBC, KBD) do not touch each other when pressing an electrical component (BE) deforms them elastically. Measuring head according to one of the preceding claims, wherein a contact spring (KF) is connected to ground. Measuring head according to one of the preceding claims, whose contact springs (KF) - have a length between 0.5 and 5 mm, - have a thickness between 50 and 150 microns and - Have a width between 100 and 500 microns. Measuring head according to one of the preceding claims with a polygonal recess (A) in the central region (ZB) through the main body (G), - With a contact spring (KF), the support area (AB) is arranged on the bottom and the contact area (KB) in the recess (A) and with the bottom of the base body (G) forms an angle α, wherein 15 ° <= α <= 75 °. Measuring head according to the preceding claim, wherein the stroke of the contact area (KB) is between 25 and 100 μm. Measuring head according to one of the preceding claims, which is connected via coaxial cables to a multi-port network analyzer. Measuring head according to the preceding claim, having a contact region (KB) which presses against a connection pad of an electrical component (BE) to be tested and thereby interconnects the multiturn network analyzer with the component (BE). Measuring head according to one of the preceding claims, further comprising a reference potential body (BPK).

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