GB2526110A

GB2526110A - Device testing

Info

Publication number: GB2526110A
Application number: GB1408522.9A
Authority: GB
Inventors: Christopher Miles Jones
Original assignee: DIAGNOSYS TEST SYSTEMS Ltd
Current assignee: DIAGNOSYS TEST SYSTEMS Ltd
Priority date: 2014-05-14
Filing date: 2014-05-14
Publication date: 2015-11-18
Also published as: GB201408522D0

Abstract

A testing apparatus and a device carrier for testing a device in accordance with a testing protocol. The testing apparatus comprises test circuitry for applying the testing protocol and a tester port for receiving a device carrier to which a device to be tested is connected. The tester port has electrical contacts coupled to the test circuitry connecting with corresponding contacts on the device carrier when the device carrier is clamped to the tester port. The electrical contacts on the device carrier are electrically coupled to a socket for receiving the device to be tested. The testing apparatus has electromagnet and the device carrier has a ferromagnetic disc armature so the device carrier can be clamped to the tester port. The clamping voltage may be reduced to maintain contact after initial clamping, for example from 12V to 2V.

Description

TITLE OF THE INVENTION

DEVICE TESTING

BACKGROUND OF THE INVENTION

The present invention relates to the field of testing of devices, for example semiconductor devices, and in particular to apparatus and methods for clamping a device for testing in a tester.

There are various scenarios in which electronic / electrical devices undergo some form of testing. For example, it is common during semiconductor manufacturing to diagnostically test devices to seek to identify if there are any problems with the manufacturing process, for example based on an analysis of observed failure rates among a random sample of devices. As another example, there is an increasing global problem with counterfeit devices entering the marketplace, and so a device may also undergo testing is to determine if the device is genuine or counterfeit.

Testing is performed by connecting a device to be tested, generally referred to as a device under test (DUT), to a testing apparatus. The testing apparatus is configured to apply electrical signals to the device and measure the response of the device to the signals in accordance with a pre-defined testing protocol for the OUT. If the OUT response to the applied signals is as expected, it may be deemed to "pass" the test. If the DUT response is not as expected, it may be deemed to "fail" the test. It will be appreciated the specific nature of the testing protocol, for example in terms of the signal to be applied and the expected responses, will depend on the nature of the DUT.

A DUT is typically connected to a testing apparatus through an intermediate device carrier I load board. That is to say, the OUT is mounted to a device carrier, and the device carrier is mounted to the testing apparatus. A testing apparatus will typically be programmable I configurable so that it can test a number of different types of device. The use of device carriers allows devices having different pin-out arrangements to be appropriately connected to the testing apparatus through a single interface. In effect the device carrier provides an adapter to convert between the arrangement of connections on the testing apparatus and the arrangement of connections on the OUTs. Thus, for each type of device having a particular arrangement of connections a different device carrier may be provided to allow that type of device to be connected to the testing apparatus. Testing apparatus may then be configured through appropriate programming to apply an appropriate testing protocol for that type of device.

A single testing apparatus may thus be used with a number of different types of device carrier for testing different types of device. In some situations a user may wish to change device carriers on a regular basis, for example where the user is regularly testing different types of device that use different device carriers or where devices which might be the same type are to remain in their own device carrier (E.g. to protect them during handling). It is therefore desirable for device carriers to be coupled to a testing apparatus (tester) in a manner which is quick and easy to use, while remaining reliable and cost-effective. Some previously-proposed approaches have involved mechanical engagement, pneumatic engagement or vacuum engagement.

However, the Inventors have recognised these existing methods can in some circumstances be subject to some drawbacks. For example, existing approaches can suffer from uneven engagement forces, which can result in unreliable electrical contacts being established between the connections on the device carrier and the corresponding connections on the testing apparatus. Existing approaches are also relatively complex, which increases cost and unreliability. Existing approaches based on vacuum engagement are less prone to mechanical failure, but can be relatively noisy and can cause contamination to be sucked into the region of the DUT and device carrier.

In view of these drawbacks, there is a need for improved mechanisms for engaging a device carrier with a testing apparatus.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a testing apparatus for testing devices in accordance with a testing protocol, the testing apparatus comprising: test circuitry for applying a testing protocol to a device to be tested; a tester port for receiving a device carrier to which a device to be tested is connected, wherein the tester port comprises a plurality of electrical contacts which are electrically coupled to the test circuitry and arranged to connect with corresponding electrical contacts on the device carrier to establish an electrical connection between the test circuitry and the device carrier when the device carrier is clamped to the tester port; and an electromagnet arrangement configured to selectively apply a clamping force to a device carrier located at the tester port to clamp the device carrier to the tester port.

In accordance with some embodiments the electrical contacts of the tester port are spring loaded, for example spring loaded pins I probes.

In accordance with some embodiments the electromagnet arrangement comprises an electromagnet (or a plurality of electromagnets) and an electromagnet control unit configured to selectively supply power to the electromagnet to selectively apply the clamping force.

In accordance with some embodiments the electromagnet control unit is configured to supply a first level of power to the electromagnet (or respective ones of a plurality of electromagnets) to initially clamp the device carrier to the tester port and to then subsequently supply a second level of power to the electromagnet (or respective ones of a plurality of electromagnets) to maintain the device carrier clamped to the tester pod, wherein the second level of power is less than the first level of power. This can help reduce the overall power consumption and efficiency of the testing apparatus.

In accordance with some embodiments the electromagnet control unit is configured to determine when a device carrier has been located at the tester port and to supply power to the electromagnet to clamp the device carrier to the tester pod in response thereto.

In accordance with some embodiments the electromagnet control unit is configured to determine when testing of a device on a device carrier clamped to the tester pod is complete and to reduce the power supplied to the electromagnet to unclamp the device carrier from the tester pod in response thereto.

In accordance with some embodiments the electromagnet is arranged around the middle of the tester port.

In accordance with some embodiments the testing circuitry is configured to determine when a device carrier has been clamped to the tester pod and to initiate the application of the testing protocol in response thereto.

In accordance with some embodiments the testing circuitry is configuied to determine an identifier associated with a device carrier clamped to the tester pod and to select a testing protocol to be applied based on the identifier associated with the device carrier.

In accordance with some embodiments a characteristic of the shape of the tester pod is configured to cooperate with a characteristic of the shape of a device carrier to be received to assist in locating the device carrier at the tester pod for clamping.

In accordance with some embodiments the characteristic of the shape of the tester pod is the shape of a boundary portion of a recess in which a device carrier is located for clamping to the tester pod.

In accordance with some embodiments the electromagnet arrangement is configured to generate a magnetic field having a shape which attracts the device carrier towards a desired alignment relative to the tester pod as it is clamped to the tester pod.

According to a second aspect of the invention there is provided a device carrier for a device to be tested using a testing apparatus for testing devices in accordance with a testing protocol, wherein the device carrier comprises: a socket for receiving a device to be tested; a plurality of electrical contacts which are electrically coupled to the socket and arranged to connect with corresponding electrical contacts of a tester pod of the testing apparatus to establish an electrical connection between the device to be tested and the testing apparatus when the device carrier is clamped to the tester pod; and an armature configured to respond to an electromagnet of the testing apparatus to selectively to clamp the device carrier to the tester port. The armature may comprises a single armature element or a plurality of armature elements.

In accordance with some embodiments the electrical contacts of the device carrier comprise electrical contact pads.

In accordance with some embodiments the device carrier is configured to provide the testing apparatus with an indication of a testing protocol to be applied for a device in the socket of the device carrier.

In accordance with some embodiments the indication of a testing protocol to be applied for a device in the socket of the device carrier comprises an indication of an identifier associated with the device carrier.

In accordance with some embodiments a characteristic of the shape of the device carrier is configured to cooperate with a characteristic of the shape of the tester port to assist in locating the device carrier at the tester port for clamping.

In accordance with some embodiments the characteristic of the shape of the device carrier is the shape of a boundary portion of a main body of the device carrier.

In accordance with some embodiments the armature comprises a ferromagnetic element.

In accordance with some embodiments the armature is arranged around the middle of a surface of the device carrier that is adjacent the tester port of the testing apparatus when the device carrier is clamped to the tester port.

According to a third aspect of the invention there is provided a testing system comprising a testing apparatus of the first aspect of the invention and a device carrier of the second aspect of the invention.

According to a fourth aspect of the invention there is provided a method of mounting a device for testing in accordance with a testing protocol, the method comprising: connecting the device to a device carrier comprising a plurality of electrical contacts which are electrically coupled to the device and arranged to connect with corresponding electrical contacts of a tester port of a testing apparatus which are electrically coupled to testing circuitry of the testing apparatus; locating the device carrier at the tester port of the testing apparatus; and activating an electromagnet to clamp the device carrier to the tester port of the testing apparatus to establish an electrical connection between the test circuitry and the device.

It will be appreciated that features and aspects of the invention described above in relation to the first and other aspects of the invention are equally applicable to, and may be combined with, embodiments of the invention according to other aspects of the invention as appropriate, and not just in the specific combinations described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described by way of example only with reference to the following drawings in which: Figure 1 schematically represents in perspective view a testing system according to certain embodiments of the invention and which comprises a tester / testing apparatus and a carrier for a device to be tested (device under test -OUT); Figure 2 schematically represents in perspective view a OUT and device carrier for use in the testing system represented in Figure 1; Figure 3 schematically represents in perspective view an underside of the device carrier represented in Figure 2; Figure 4 schematically represents in perspective view a tester port of the tester! testing apparatus represented in Figure 1 for receiving the device carrier represented in Figures 2 and 3; Figure 5 is a flow diagram schematically representing a method of operating the testing system of Figure 1; Figure 6 schematically represents in vertical cross-section the tester port and the device carrier for the testing system represented in Figure 1 prior to a clamping engagement being established between them; and Figure 7 schematically represents in vertical cross-section portions of the tester port and the device carrier for the testing system represented in Figure 1 when clamped together.

DETAILED DESCRIPTION

Aspects and features of certain examples and embodiments of the present invention are discussed / described herein. Some aspects and features of certain examples and embodiments may be implemented conventionally and these are not discussed / described in detail in the interests of brevity. It will thus be appreciated that aspects and features of apparatus and methods discussed herein which are not described in detail may be implemented in accordance with any conventional techniques for implementing such aspects and features.

Figure 1 schematically represents in perspective view a testing system 2 according to certain embodiments of the invention. The testing system 2 in this particular example is used for diagnostic testing of electronic! electrical devices. However, it will be appreciated similar testing systems could equally be used for non-diagnostic testing purposes (i.e. the purpose of the testing is not significant). The diagnostic testing system 2 comprises two main components / assemblies, namely a testing apparatus 4 and a device carrier 6 for receiving a device under test (OUT). In one example the testing apparatus 4 has a footprint of around 42 cm x 26 cm and a height of around 15 cm and the device carrier 6 has characteristic dimensions of around 10 cm x 10 cm x 1 cm. However, it will be appreciated the size and shape of the testing apparatus and associated device carrier 6 are not of primary significance and may be selected according to the implementation at hand, for example having regard to the size of devices to be tested and the number of electrical connections to be established between the testing apparatus and a device under test.

The testing apparatus 4 has a tester pod (interface) 8 arranged to receive the device carrier 6. The tester port 8 provides both a physical interface and an electrical interface for coupling the device carrier 6 to the testing apparatus 4. Thus, in normal use a OUT is mounted on the device carrier 6, and the device carrier 6 is coupled to the tester port 8 of the testing apparatus 4. This establishes an electrical connection between testing circuitry (not shown) within the testing apparatus 4 and the OUT. The testing circuitry within the testing apparatus 4 may then be activated to apply electrical signals to the OUT and monitor the response of the OUT to the applied signals in accordance with a defined testing protocol for the OUT. In this regard the operation of the testing apparatus 4 in terms of how the testing protocol is applied may be in accordance with conventional techniques. However, an aspect of diagnostic testing systems in accordance with embodiments of the invention is the manner in which the device carrier 6 and the testing apparatus 4 are engaged and disengaged. Once the device carrier 6 and testing apparatus 4 are engaged in accordance with an embodiment of the invention and the OUT is ready for testing, the operation of the diagnostic testing system in actually testing the OUT using an appropriate testing protocol may be performed generally in accordance with any known techniques for diagnostic device testing.

Figures 2 and 3 schematically represent perspective views the device carrier 6 of the testing system 2 shown in Figure 1. Figure 2 shows the device carrier 6 along with a device to be tested (OUT) 10 from above while Figure 3 shows the device carrier 6 from below (the DUT 10 is not visible in this view). It will be appreciated that terminology such as "above" and "below", and "top" and "bottom", etc., and other orientation dependent terms will be used herein having regard to a testing system in use in the orientation represented in Figure 1. This is purely for the sake of convenient explanation and it will be appreciated the use of such terms should not be interpreted as limiting embodiments of the invention to use in any particular orientation.

For example, the system of Figure 1 could equally be used on its side or upside down relative to the orientation adopted in Figure 1.

As represented in Figure 2, the device carrier 6 comprises a circuit board 12, a carrier body 14 and a OUT socket 16. The circuit board 12 may be of conventional construction, for example comprising a fibreglass substrate with copper and br gold conductive tracks and pads arranged thereon. The OUT 10 in this example is a semiconductor chip. The DUT socket 16 is a conventional socket of the kind used for connecting a semiconductor chip to a circuit board.

Thus, when the DUT 10 is placed in the socket 16, an electrical connection is established between connector pins of the OUT 10 and various conductive tracks and pads on the circuit board 12 in the usual way. The OUT 10 may be held in place using a hinged clamp 18 associated with the socket 16, again in accordance with conventional techniques.

As can be seen in Figure 3, the underside of the circuit board 12 comprises an array of electrical connections in the form of contact pads arranged into a plurality of groups distributed around the perimeter of the circuit board 12. In this example there is a total of 656 pads arranged into eight groups, with each group comprising a generally rectangular array of pads (although not all locations in the rectangular array have a pad). At least some of the pads 22 are electrically connected via traces on the circuit board to respective connector pins of the OUT 10 when the OUT 10 is located in the socket 16. That is to say, electrical signals can be applied to the connector pins of the DUT 10 by applying the signals to corresponding ones of the pads 22 on the underside of the circuit board 12 comprising the device carrier 6. The specific mapping between respective ones of the contact pads 22 and connector pins of the OUT 10 is defined by the arrangement of tracks on the circuit board. The specific mapping used for any given device carrier is not significant since in general the testing apparatus 4 can be programmed to take account of the mapping to apply the relevant testing protocol for the OUT 10 (i.e. to apply the relevant signals to the relevant pins).

The carrier body 14 in this example comprises a plastics material, for example Oupont Delrin (RTM) (which is a polyoxymethylene-based material), but any other suitable material may be used, for example PET (polyethylene terephthalate). The carrier body 14 in this example is formed of a single element comprising a number of locating tabs 24 arranged around a generally square central portion 26. In this example there are eight locating tabs 24, namely one extending outwardly from each corner and from the centre of each side of the generally square central portion 26. These tabs 24 provide a "key" for helping to properly aligning the device carrier 6 with the tester port 8 of the testing apparatus 4 during use. The carrier body 14 may, for example, be formed by machining a block of material or by injection moulding. However, any conventional manufacturing technique could be used, such as three-dimensional printing Mounted within the central portion 26 of the carrier body 14, generally around the centre of the device carrier 6, is a ferromagnetic armature 28. The armature 28 in this example is in the form of a circular mild steel disc having a diameter of around 4 cm and a thickness of around 0.5 cm. The armature 28 is mounted so that its lower surface (shown uppermost in Figure 3) is exposed but recessed slightly within the carrier body 14, for example by around 1 mm. The armature 28 may be mounted in the carrier body 14 using any appropriate technique, for example the armature 28 could be held in an appropriately-sized opening by glue I epoxy I screw(s) I interference fit, or could be moulded into the carrier body 14 during manufacture.

The circuit board 12 is mounted to the upper side of the carrier body 14 (i.e. a side opposite to the armature 28) using an appropriate fixing mechanism, such as screws or clips (screws are used in the example seen in Figure 2). The circuit board 12 extends beyond the central square central portion 26 of the carrier body 14 such that the pads 22 on the underside of the circuit board 12 are accessible in the spaces between the locating tabs 24 extending outwardly from the central square central portion 26 of the carrier body 14.

Figure 4 schematically represents a magnified view of the tester port 8 of the diagnostic tester 4. The tester port 8 comprises a recess 36 having a size and shape which generally matches that of the main body 14 of the device carrier 6. Arranged around the periphery of the recess 36 are eight probe holder blocks 32. These are sized and positioned to fit in the gaps between the locating tabs 24 extending outwardly from the central square central portion 26 of the carrier body 14 when the device carrier 6 is located in the recess 36 tester port 8. Each probe holder blocks 32 comprises an array of electrical contacts 34 in the form of spring-loaded pins I probes. At least some of the probes 34 are electrically connected to the testing circuitry within the testing apparatus 4. In this example there is a total of 656 probes spread around the eight probe holder blocks 32 in a pattern that corresponds with the arrangement of contact pads 22 on the underside of the circuit board 12 of the device carrier 6. Accordingly, when a device carrier 6 is mounted to the tester port 8 of the testing apparatus 4 local contacts are established between the testing circuitry of the testing apparatus 4 and the device carrier 6 (and hence to a DUT mounted to the socket 16 of the device carrier 6) via respective ones of the spring-loaded probes 34 of the tester port 8 and the corresponding contact pads 22 of the device carrier's circuit board 12. It will, of course, be appreciate that while the arrangement represented in Figure 4 allows for up to 656 probes 34 (and corresponding contact pads 22), and some implementations not all locations for probes will be used. For example, if the testing apparatus 4 is intended to only ever to be used for testing devices having 300 or fewer pins, only 300 probes may be provided (potentially with some extras to allow for continued operation should one or more pins fail).

The spring-loaded probes 34 may be constructed and mounted within their respective probe holder blocks 32 in accordance with conventional techniques for providing spring-loaded electrical contacts. In this particular example the probes 34 are configured to protrude from the upper surface of their respective probe holder blocks by around 0.5 mm. In their rest state the probes are pre-loaded to around 0.2 mm compression, which for the probes used this example means a force of around 0.136 N is required to compress each pin I probe further. This means for a fully populated interface (i.e. comprising 656 spring-loaded probes), a force of around 90 Newtons is needed to compress the spring-loaded probes, and by applying such a force to a device carrier located in the recess 36 a reliable connection between the respective probes 34 of the tester port 8 and contact pads 22 of the device carrier 6 can be established. However, it will be appreciated the actual force needed to clamp the device carrier 6 to the tester port 8 to establish a reliable electrical connection between the testing circuitry of the testing apparatus 4 and a device under test 10 mounted to the device carrier 6 via the probes 34 and pads 22 will be different in different implementations. In particular the required clamping force will depend on degree of resilience and pre-loading of the probes and the number of them.

As noted above, in existing diagnostic testing systems a required clamping force to hold a device carrier against a testing apparatus may be provided using mechanical or vacuum techniques. However, in accordance with embodiments of the present invention, the device carrier 6 is clamped to the tester port 8 of the testing apparatus 4 using an electromagnet arrangement. In particular, the testing apparatus is provided with an electromagnet 30 arranged around the middle of the tester port 8 so as to align with the ferromagnetic armature 28 of the device carrier 6 when the device carrier 6 is placed in the tester port. The testing apparatus further comprises an electromagnet control unit (not shown) that is configured to selectively supply power to the electromagnet 30 to selectively activate the magnet to apply a clamping force. The electromagnet 30 comprises a conventional electromagnet, for example in the form of a solenoid having an iron core surrounded by an electrical winding in the usual way.

Figure 5 is a flow diagram schematically representing a method of operating the testing system 2 represented in Figure ito apply a desired testing protocol to a device 10. The specific details of the testing protocol to be applied to the device are not significant.

In step Si the device 10 is mounted in the device carrier 6. In particular, the device 10 is placed in the socket 16 of the device carrier and retained in position using the hinged clamp 18.

When the device 10 is mounted in the socket an electrical connection is established between the connector pins of the device 10 and respective pads 22 on the underside of the circuit board 12 comprising the device carrier 6 as discussed above. It will be appreciated that connections need only be established in respect of the connector pins of the device 10 which are relevant for applying the testing protocol. For example, if there are certain connector pins of the device 10 that are not used during the testing process, these need not be connected to any of the contact pads 22. The specific connector pins of the device 10 that need to be accessed during testing will depend on the testing protocol in the usual way.

In step S2 the device carrier 10 is located in the tester port 8. In particular, the main body 14 of the device carrier 6 is located in the recess 36 of the tester port 8 so the device carrier is supported by the underside of the circuit board 12 resting on the tops of the spring-loaded probes 34. This may be achieved by a user manually placing the device carrier 6 in the appropriate position, or may be performed using an automated robot system. As discussed above, the locating tabs 24 provide a "key" for helping to properly align the device carrier 6 with the tester port 8 of the testing apparatus 4. In particular, the shape of the outer periphery of the main body 14 of the device carrier 6 is arranged to match the shape of the recess 36 of the tester port 8 so the device carrier 6 is readily located with its contact pads 22 in alignment with the relevant corresponding probes 34 of the tester port 8. In some examples the respective shapes of the device carrier and the recess 36 of the interface I tester port 8 may be configured so the device carrier 6 can only be positioned in the recess 36 in one orientation. For example, the outer profile of the device carrier 6 and recess 36 may have not any rotational symmetry and / or may have a locating peg may be provided in the floor of the recess 36 to align with a corresponding hole in the main body 26.

Figure 6 schematically represents some aspects of the device carrier 6 and tester port 8 I testing apparatus 4 in vertical cross-section at the end of step S2 of the method represented in Figure 5. The cross-section is in a plane that runs close to the centre of the electromagnet 30 and passes through some of the probes 34 on opposite sides of the electromagnet 30. The various elements of the device carrier and the tester port 8 discussed above are identified in Figure 6 using the same reference numerals. Also seen in Figure 6 is a circuit board 40 associated with the tester port 8. The respective probes 34 comprising the tester port 8 are in electrical contact with contact pads 42 on the tester port circuit board 40. Conductive traces on the tester port circuit board 40 provide a connection between the testing circuitry of the testing apparatus 4 and the probes 34. As schematically represented in Figure 6, the circuit board 12 of the device carrier 6 initially rests upon the probes. The ferromagnetic armature 28 of the device carrier and the electromagnet 30 of the tester port 8 are arranged in this particular example so that when the device carrier 6 is placed in the recess 36 of the tester port 8 so that it rests upon the spring-loaded probes, there is a gap of around 0.5 mm between the armature 28 and the electromagnet 30, as schematically represented in the figure.

Returning now to the method of operation represented in Figure 5, after the device carrier 6 is placed in the test port 8 in step S2, the method proceeds to step S3 in which the electromagnet (EM clamp) 30 is activated. Activating the electromagnet 30 is achieved by supplying electrical power to the electromagnet 30 in the usual way. In this example the testing apparatus 4 includes an electromagnet control unit that is configured to automatically activate the electromagnet 30 when the device carrier 6 has been placed in the tester port 8 in step S2.

There are various ways in which the electromagnet control unit can determine when the device carrier 6 is placed in the tester port 8. For example, the tester port 8 may be associated with an optical sensor which is obscured when a device carrier 6 is located at the tester port 8. In another example, the tester port 8 may be associated with a switch that is activated by the weight of the device carrier 6. In yet another example, the circuit board 12 of the device carrierS may comprise a trace connecting between a particular pair of contact pads 22 associated with a particular pair of probes 34, and the electromagnet control unit may be configured to identify when these two probes become electrically connected together. In this case it may be preferable for the tips of the probes 34 responsible for sensing the presence of the device carrier 6 to be located slightly higher than for other probes so they contact their contact pads before the other probes take the weight of the device carrier 6.

In this particular example the testing system 2 is configured so that when a 12 V power supply is applied to the electromagnet 30 a force of 120 Newton is exerted between the electromagnet 30 and the ferromagnetic armature 28 when they are separated by 0.5 mm (as in Figure 6). This force is sufficient to overcome the resilience of the spring-loaded probes so the device carrier 6 is pulled further into the recess 36 of the tester port 8 as the ferromagnetic armature 28 is attracted by the electromagnet 30. As the spring-loaded probes are compressed, they exert a linearly increasing force against further compression (in accordance with Hooke's law). However, as the gap between the armature and the electromagnet decreases in correspondence with the increased compression of the spring-loaded probes, the force applied to the ferromagnetic armature by the electromagnet increases exponentially. Accordingly, once the electromagnet supplies sufficient force to overcome the initial resilience of the spring-loaded probes (pogo pins), it can continue to compress the probes despite their increased resistance.

As the probes are compressed in their housings they are pressed against corresponding pads on the device carrier. Accordingly, when the device carrier 8 is clamped to the tester port 8 by the electromagnet 30, the spring-loaded probes 34 establish electrical contact with their corresponding pads 22 on the device carrier. As discussed above, the spring-loaded probes 34 are electrically coupled to the testing circuitry and the contact pads 22 on the device carrier 6 are electrically coupled to the device under test. Accordingly, when the electromagnet is activated (energised) to clamp the device carrier to the tester port, the testing circuitry of the testing apparatus 4 is connected to the device under test 10. At this stage the device is ready for testing.

Figure 7 schematically represents some aspects of the device carrier 6 and tester port 8 / testing apparatus 4 in vertical cross-section at the end of step S3 of the method represented in Figure 5. The cross-section is in the same plane as the cross-section of Figure 6, but shown on a magnified scale. As can be seen in Figure 7, the 0.5 mm gap between the electromagnet 30 and the ferromagnetic armature 28 is closed as the device carrier 6 is clamped to the tester port 8 by the force of the energised electromagnet. Thus in this example the device carrier 6 bottoms out in the recess 36 of the interface 8 when the probes 34 are compressed by 0.5 mm from their rest state (which as noted above includes 0.2 mm pre-loading). The probes 34 are configured to compress by more than this amount to help reduce any risk of damaging the probes 34 through over-compression.

In some example configurations the relative arrangement of the armature 28 and the shape of the magnetic field generated by the electromagnet 30 may be configured to assist in properly aligning the device carrier 6 in the interface 8. For example, a solenoid-based electromagnet will generate an magnetic field shape which is generally circularly-symmetric and axial and this will naturally tend to attract a corresponding-sized armature towards the centre of the electromagnet. Accordingly, instead of! or in addition to providing the interface 8 and the device carrier 6 with cooperating shapes to aid alignment, the arrangement of the magnetic field generated by the electromagnet(s) and/or armature(s) associated with the device carrier and interface can be configured to bring these two elements into a desired alignment during clamping. This may be done in accordance with established techniques for magnetic positioning. In step S4 represented in Figure 5, the testing apparatus 4 applies the relevant test protocol for the device 10 in the device carrier 6. As already noted above, the exact nature of the test protocol is not relevant here. In this particular example the device carrier 6 is configured provide the testing apparatus 4 with an indication of a testing protocol to be applied for a device on the device carrier. This may be applicable, for example, in an implementation in which the testing apparatus is programmed to apply different testing protocols for different devices. The indication may be provided in any of a number of ways. In one example the device carrier may comprise a carrier control unit that is configured to communicate with the testing circuitry within the testing apparatus in accordance with a pre-defined communication protocol over connections established by some of the probes and contact pads. In another example the circuit board 12 of the device carrier 6 may comprise traces that interconnect various probes according to one of several pre-defined combinations to identify the testing protocol to be applied. For example, the device carrier may interconnect a first contact pad associated with a first probe with a second contact pad associated with a second probe to identify a particular testing protocol should be applied for the device carrier, while another device carrier may interconnect the contact pad associated with the first probe with a third contact pad associated with a third contact probe to identify a different testing protocol should be applied. The testing apparatus can thus establish which arrangement of probes are interconnected and apply the relevant testing protocol. In yet another example the identification information may come from the device itself When the testing protocol has been applied, the testing apparatus may provide a suitable indication of the outcome in accordance conventional techniques. For example, a simple pass/fail light system may be used. Alternatively, the testing apparatus may provide additional information, for example an indication of the nature of any failure that has been identified. This aspect of the operation of the testing apparatus may be conventional.

Once the test procedure is complete, the method proceeds to step S5.

In step S5, the electromagnet 30 is de-activated to release the clamping force on the device carrier 6. This is achieved by removing the supply of power to the electromagnet. In this example the electromagnet control unit is configured to automatically de-activate the electromagnet 30 when the test procedure is complete. There are various ways in which the electromagnet control unit can determine when the testing of the device is complete. For example, the testing circuitry may be configured to provide an indication to the electromagnet control unit when it should release the device carrier 6. In another example, the electromagnet control unit may be configured to simply release the device after a given time has elapsed on the assumption the testing circuitry will have completed testing within this time.

In step S6 the device carrier is removed from the tester port. Again, this may be performed manually by user, or automatically in a robotic testing implementation.

In step S7 the device is removed from the device carrier. This represents the end of the testing process. Another device may be inserted in the device carrier and tested as above.

Alternatively, a different type of device may be placed in a different device carrier and tested, again using the same general procedure described above. In some implementations the device may remain in its device carrier for an extended period after the device carrier is removed from the testing apparatus, for example to provide continued protection during further handling and / or testing. In this case the next device to be tested may be provided with its own device carrier, even if this is of the same type as a previously tested device.

Thus the method represented in Figure 5 may be used for testing a device using the testing system 2 of Figure 1 in accordance with certain embodiments of the invention. The Inventors have found this approach provides various advantages over existing testing systems and methods. For example, the self-aligning associated with the cooperating shapes of the device carrier and tester port allow for relatively quick, repeatable and simple loading. The degree of matching in the shapes can be selected to ensure correct operation over a range of expected temperatures to reduce the risk of thermal expansion or contraction causing jamming.

From the perspective of a user there is a reduced risk of strain injury from repeated activation of a manual clamping mechanism. The approach has very few moving parts and so is mechanically robust. The main moving parts are the spring-loaded probes, but these can be based on well-established technologies, for example off-the-shelf spring-loaded probes may be used in accordance with certain embodiments of the invention. The lack of moving parts also means the arrangement is relatively simple from a mechanical perspective, which helps reduce cost compared to existing designs, and can help make the testing apparatus easier to repair if any failure does occur. As compared to existing techniques based on vacuum clamping, there is no need for any vacuum pumps or compressed air, which again leads to a generally simpler approach. The Inventors have also found the approach can provide for a uniform distribution of clamping force to ensure a reliable degree of electrical connection between all probes associated with the tester port and their corresponding contact pads associated with a device carrier. Another advantages is the ease of automation that can be achieved with an electromagnet clamp arrangement. Furthermore, the tester port is relatively simple and easy to keep clean and requires no lubrication, which can assist with integration in clean environments.

It will be appreciated there are many variations and modifications that can be made to the testing apparatus and method of testing described above in accordance with other embodiments of the invention.

For example, in accordance with certain embodiments the electromagnet arrangement used for clamping the device carrier to the tester port of the testing apparatus may be configured to reduce the clamping force once the device carrier 6 has become clamped to the tester port 8. That is to say, the electromagnet arrangement may be supplied with a first level of power to initially clamp the device carrier to the tester port and then subsequently supplied with a second level of power to maintain the device carrier clamped to the tester port, wherein the second level of power is less than the first. This follows from the Inventors' recognition that the power required to initially clamp the device carrier to the tester port (i.e. the power needed to go from the situation represented in Figure 6 to the situation represented in Figure 7) is greater than the power needed to maintain the device carrier clamped against the tester port (i.e. to maintain the situation represented in Figure 7). This is because, as noted above, a given voltage will provide a higher clamping force as the distance between the electromagnet and the armature is decreased. Thus, in one example the electromagnet control unit may be configured to apply 12 V to energise the electromagnet in step S3 as discussed above, and then may be configured to reduce the (effective) voltage to 2 V throughout the testing procedure represented in step S4. This reduction in power applied to the electromagnet has been found to allow the device carrier to remain clamped to the tester port while using less power than would be the case if the supply continued at 12 V. In general a testing apparatus 4 in accordance with an embodiment of the invention may be configured to allow the initial voltage to be applied to initially clamp a device carrier to the tester port, and the subsequent lower voltage used to retain the device carrier in a clamped position during application of the testing protocol, to be determined empirically during an initial set-up step procedure. The reduction in power provided to the electromagnet may be achieved in any of a number of ways. For example, modulation, such as pulse width modulation, may be applied to an otherwise fixed voltage power supply with a duty-cycle corresponding to a desired reduction in power. Conventional smoothing techniques, for example using a capacitor connected in parallel with the electromagnet, may be adopted to reduce the temporal variation in power supplied to the electromagnet as a result of the modulation scheme if desired. Thus, as one example, a continuous 12 V power supply may be used to drive the electromagnet during initial clamping, and then the 12 V power supply may be modulated with a one-sixth duty cycle to provide an effective voltage of 2 V during testing. It will be appreciated that any other established techniques for varying the output of an electrical power supply could equally be used.

There are also other variations to the testing apparatus described above that can be applied. For example, instead of having an electromagnet control unit responsible for automatically activating and deactivating the electromagnet, the testing apparatus 4 may instead be simply provided with a switch arrangement to allow a user to manually control the electromagnet. Similarly, rather than have the testing apparatus automatically determine the test protocol to be applied, a user may indicate this manually, for example again using a switch arrangement to identify the testing protocol to be applied.

For example, while the above-described embodiments have primarily focussed on an implementation in which a single device to be tested is mounted to a device carrier, in other examples a device carrier may be configured to carry multiple devices for testing together.

Furthermore, while the above-described embodiments have primarily focussed on testing for diagnostic purposes, the same principles can be applied for testing / analysing devices for other purposes which might not be considered diagnostic purposes. For example, the same principles can be used for testing devices to establish one or more aspects of their performance characteristics which might vary from device to device, for example because of manufacturing variations. That is to say, the nature of any testing to be performed once a device has been coupled to a testing apparatus in accordance with an embodiment of the invention is not significant.

It will also be appreciated the specific nature of the device to be tested is not significant, and whereas the above-described embodiments have primarily been described in the context of testing a device in the semiconductor chip package, the same principles apply regardless of the type of device. For example, in another example the device to be tested may comprise a circuit board / circuit board assembly having a plurality of electrical / electronic components. By way of one specific non-limiting example, the device to be tested may comprise a circuit board assembly having a plurality of passive and / or active electric electronic components forming a tuned circuit and the tester may be configured to measure as aspect of the frequency response of the tuned circuit.

It will also be appreciated that different configurations of electromagnet arrangement may be used. For example, rather than using a single-element electromagnet and single-element armature, such as represented in Figures 3 and 4, in another example of the electromagnet arrangement may comprise a plurality of electromagnets and / a plurality of separate armature elements. For example, a plurality of electromagnets and a plurality of armature elements may be provided in a configuration which aids alignment as the device carrier is brought into contact with the interface. For example, in addition to a central electromagnet 30 and armature 28 as represented in Figure 3 and 4, there may in some embodiments be an additional electromagnet and armature provided at a coiner of the interface and device carrier to aid with rotational alignment of these elements during clamping.

It will also be appreciated the principles described above are readily scalable so that larger (or indeed smaller) configurations or configurations with more dense arrangement of probes can be readily provided. For example, there is an ongoing trend in most electronic technologies towards smaller devices with an associated increase in density of great arrangements. With an increased density of connector arrangements comes a greater force per unit area of probes, and this can readily be accommodated for by increasing the strength of the electromagnet arrangement, for example by increasing the size and I or current for a single electromagnet, or by providing additional electromagnets and corresponding armature elements. The rigidity of the interface 8 and/or device carrier 6 can readily be increased to accommodate greater clamping forces if flexing is a concern, for example by using thicker and / or stronger materials in their construction.

Thus there has been described a testing apparatus and a device carrier for testing a device in accordance with a testing protocol. The testing apparatus comprises test circuitry for applying the testing protocol and a tester port for receiving a device carrier to which a device to be tested is connected. The testing apparatus tester port comprises a plurality of electrical contacts which are electrically coupled to the test circuitry and arranged to connect with corresponding electrical contacts on the device carrier when the device carrier is clamped to the tester port. The electrical contacts on the device carrier are electrically coupled to a socket for receiving the device to be tested. The testing apparatus comprises an electromagnet and the device carrier comprises a ferromagnetic armature so the device carrier can be selectively clamped to the tester port to establish an electrical connection between the testing circuitry and the device by selective activation of the electromagnet.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. It will be appreciated that features of the dependent claims may be combined with features of the independent claims in combinations other than those explicitly set out in the claims.

Claims

CLAIMSWhat is claimed is: 1. A testing apparatus for testing devices in accordance with a testing protocol, the testing apparatus comprising: test circuitry for applying a testing protocol to a device to be tested; a tester port for receiving a device carrier to which a device to be tested is connected, wherein the tester port comprises a plurality of electrical contacts which are electrically coupled to the test circuitry and arranged to connect with corresponding electrical contacts on the device carrier to establish an electrical connection between the test circuitry and the device carrier when the device carrier is clamped to the tester port; and an electromagnet arrangement configured to selectively apply a clamping force to a device carrier located at the tester port to clamp the device carrier to the tester port.
2. The testing apparatus of claim 1, wherein the electrical contacts of the tester port are spring loaded.
3. The testing apparatus of any preceding claim, wherein the electrical contacts of the tester port are spring loaded pins.
4. The testing apparatus of any preceding claim, wherein the electromagnet arrangement comprises an electromagnet and an electromagnet control unit configured to selectively supply power to the electromagnet to selectively apply the clamping force.
5. The testing apparatus of claim 4, wherein the electromagnet control unit is configured to supply a first level of power to the electromagnet to initially clamp the device carrier to the tester port and to then subsequently supply a second level of power to the electromagnet to maintain the device carrier clamped to the tester port, wherein the second level of power is less than the first level of power.
6. The testing apparatus of claim 4 or 5, wherein the electromagnet control unit is configured to determine when a device carrier has been located at the tester port and to supply power to the electromagnet to clamp the device carrier to the tester port in response thereto.
7. The testing apparatus of any of claims 4 to 6, wherein the electromagnet control unit is configured to determine when testing of a device on a device carrier clamped to the tester port is complete and to reduce the power supplied to the electromagnet to unclamp the device carrier from the tester port in response thereto.
8. The testing apparatus of any of claims 5 to 7, wherein the electromagnet is arranged around the middle of the tester pod.
9. The testing apparatus of any preceding claim, wherein the testing circuitry is configured to determine when a device carrier has been clamped to the tester pod and to initiate the application of the testing protocol in response thereto.
10. The testing apparatus of any preceding claim, wherein the testing circuitry is configured to determine an identifier associated with a device carrier clamped to the tester port and to select a testing protocol to be applied based on the identifier associated with the device carrier.
11. The testing apparatus of any preceding claim, wherein a characteristic of the shape of the tester pod is configured to cooperate with a characteristic of the shape of a device carrier to be received to assist in locating the device carrier at the tester pod for clamping.
12. The testing apparatus of claim 11, wherein the characteristic of the shape of the tester port is the shape of a boundary portion of a recess in which a device carrier is located for clamping to the tester port.
13. The testing apparatus of any preceding claim, wherein the electromagnet arrangement is configured to generate a magnetic field having a shape which attracts the device carrier towards a desired alignment relative to the tester port as it is clamped to the tester port.
14. A device carrier for a device to be tested using a testing apparatus for testing devices in accordance with a testing protocol, wherein the device carrier comprises: a socket for receiving a device to be tested; a plurality of electrical contacts which are electrically coupled to the socket and arranged to connect with corresponding electrical contacts of a tester port of the testing apparatus to establish an electrical connection between the device to be tested and the testing apparatus when the device carrier is clamped to the tester port; and an armature configured to respond to an electromagnet of the testing apparatus to selectively to clamp the device carrier to the tester port.
15. The device carrier of claim 14, wherein the electrical contacts of the device carrier comprise electrical contact pads.
16. The device carrier of claim 14 or 15, wherein the device carrier is configured to provide the testing apparatus with an indication of a testing protocol to be applied for a device in the socket of the device carrier.
17. The device carrier of claim 16, wherein the indication of a testing protocol to be applied for a device in the socket of the device carrier comprises an indication of an identifier associated with the device carrier.
18. The device carrier of any of claims 14 to 17, wherein a characteristic of the shape of the device carrier is configured to cooperate with a characteristic of the shape of the tester port to assist in locating the device carrier at the tester port for clamping.
19. The device carrier of claim 18, wherein the characteristic of the shape of the device carrier is the shape of a boundary portion of a main body of the device carrier.
20. The device carrier of any of claims 14 to 19, wherein the armature comprises a ferromagnetic element.
21. The device carrier of any of claims 14 to 20, wherein the armature is arranged around the middle of a surface of the device carrier that is adjacent the tester port of the testing apparatus when the device carrier is clamped to the tester port.
22. A testing system comprising the testing apparatus of any of claims 1 to 12 and the device carrier of any of claims 14 to 21.
23. A method of mounting a device for testing in accordance with a testing protocol, the method comprising: connecting the device to a device carrier comprising a plurality of electrical contacts which are electrically coupled to the device and arranged to connect with corresponding electrical contacts of a tester pod of a testing apparatus which are electrically coupled to testing circuitry of the testing apparatus; locating the device carrier at the tester pod of the testing apparatus; and activating an electromagnet to clamp the device carrier to the tester port of the testing apparatus to establish an electrical connection between the test circuitry and the device.
24. An apparatus substantially as hereinbefore described with reference to Figures 1 to 7 of the accompanying drawings.
25. A method substantially as hereinbefore described with reference to Figures ito 7 of the accompanying drawings.