BACKGROUND OF THE INVENTION

The invention relates to a bond testing apparatus, in particular for determining a strength of a bond and/or a material present on a substrate.

Electrical connections in semiconductor and electronic assemblies often include bonds and it is known that these can be mechanically tested as a means of measuring their quality. One such test is done on a system known as a bond testing apparatus and is known as a shear test. For performing such test, a part of the bond tester known as a shear tool loads the bond or material mounted on the substrate to either a specific load or until a failure of some type occurs. During this shearing or bond testing the force in the shear direction more or less parallel to the plane defined by the substrate is measured. After shear test is performed, the sheared surface is also visually inspected.

The accuracy of the positional alignment of the shear tool with reference to the location of the bond present on the substrate is known to be of great importance. In the known art a number of designs exist to obtain the best accuracy as possible regarding the positional alignment of the shear tool with reference to the location of the bond. In line with the three dimensions of space there are three alignments of the shear tool with respect to the location of the bond.

This disclosure pertains to one of these alignments, which is known as the “shear height”. The “shear height” is the distance between the (tip of the) shear tool and the surface of the substrate next to the bond or material under test, seen in the z-direction normal to the surface of the substrate. The accuracy of this height alignment is the most important for performing an accurate bond test and the “shear height” should be set and maintained as accurate as possible before and during the shear test. This accuracy is however often limited to that possible with the known bond testing technology.

It is an object to provide an improved bond testing apparatus in which the “shear height” can be set more accurately, allowing bond tests to be performed more accurately.

DESCRIPTION OF THE INVENTION

In a first example of the disclosure a bond testing apparatus is proposed for determining a strength of a bond and/or a material present on a substrate, wherein the apparatus at least comprises a frame housing; a displacement unit for displacing the frame housing in a direction normal to a plane defined by the substrate; a shear tool component accommodated in the frame housing and arranged for applying a shear force to the bond and/or the material in a direction parallel to the plane defined by the substrate; and a shear height setting unit accommodated in the frame housing, wherein the shear height setting unit is arranged to determine, during a first operational condition of the displacement unit displacing the frame housing in a direction towards the substrate, when the shear tool component comes in contact with the substrate, thereby obtaining a contact height, and to move, during a second operational condition of the displacement unit not displacing the frame housing, the shear tool component relative to the frame housing in a direction away from the substrate to set a shear height of the shear tool component based on the contact height.

Accordingly, the “shear height” can be set far more accurately compared to prior art bond test configurations. With this example, only the shear tool component is being displaced for setting the shear height. Thus, a limited amount of mass is being displaced, and because all these movements are done locally a very high accuracy can be obtained. Because of the limited mass displacement and local movement, the bond test apparatus according to the disclosure can be operated very accurately and allow shear height settings in the submicron range.

Preferably in an example, the shear height setting unit comprises a sensor element mounted between the shear height setting unit and the frame housing, wherein the sensor element is one chosen from a group of a capacitive distance sensor element, an optical distance sensor element or a linear variable displacement transducer element. As such, it is possible to accurately determine the moment the shear tool component ‘touches’ the substrate surface, this being essential for the following setting of the shear height.

In a further example of the disclosure, the shear height setting unit comprises a height actuator unit mounted between the shear height setting unit and the frame housing, the height actuator unit arranged, during the second operational condition, in moving the shear tool component relative to the frame housing in a direction away from the substrate. Because the height actuator unit only needs to displace the shear tool component relative to the frame housing in a direction away from the substrate, the overall mass displacement is limited and also a limited number of parts are involved, the stiffness in shear direction can be very high thus ascertaining an improved accuracy in the shear height setting, in particular in the submicron range.

In a preferred example, the height actuator unit comprises a piezoelectric actuator element as well as an electromagnet connecting unit arranged for mechanically connecting, during the second operational condition, the piezoelectric actuator element with the shear tool component. In particular, the shear tool component comprises a contact flange element made of a magnetic material (or a ferromagnetic material). The contact flange element made of a (ferro)magnetic material will just graze the electromagnet connecting unit in the first operational condition, during which the electromagnet connecting unit is de-activated. In the second operational condition the electromagnet connecting unit will be activated and the contact flange element and the shear tool component will be mechanically coupled to the electromagnet connecting unit and the piezoelectric actuator element. This mechanical interconnection due to magnetic force, allows the piezoelectric actuator element to accurately displace up and down and lift the shear tool component to the required shear height.

In yet another second example of the disclosure, a bond testing apparatus is proposed for determining a strength of a bond and/or a material present on a substrate, wherein the apparatus at least comprises a frame housing; a displacement unit for displacing the frame housing in a direction normal to a plane defined by the substrate; a shear tool component accommodated in the frame housing and arranged for applying a shear force to the bond and/or the material in a direction parallel to the plane defined by the substrate; and a shear height setting unit accommodated in the frame housing, wherein the shear height setting unit is arranged to determine, during a first operational condition of the displacement unit displacing the frame housing in a direction towards the substrate, when the shear tool component comes in contact with the substrate, thereby obtaining a contact height, and to move, during a second operational condition of the displacement unit not displacing the frame housing, the shear tool component relative to the frame housing in a direction away from the substrate to set a shear height of the shear tool component based on the contact height. According to this example, the height actuator unit comprises a motor like but not limited to a voice coil actuator element to accurately displace up and down and lift the shear tool component to the required shear height.

In both first and second examples, the shear height setting unit may further comprise a control unit arranged to control the first and second operational conditions of the displacement unit and/or the electromagnet connecting unit.

In particular the control unit is arranged to apply - during the first operational condition - a decreasing alternating current to the then deactivated electromagnet connecting unit in order to reduce remnant magnetism present in the electromagnetic unit to a required amount. Any remnant magnetism will induce a small attracting force on the contact flange element made of a (ferro)magnetic material causing unwanted some friction between the shear tool component and the height actuator unit. The remnant magnetic force can be beneficial in ensuring the flange element remains in contact with the elector magnet but with a controlled amount of contact friction.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to the accompanying drawings, which drawings show in:

Figure 1 a first example of an apparatus for determining a strength of a bond and/or a material present on a substrate according to the disclosure;

Figure 2 a second example of an apparatus for determining a strength of a bond and/or a material present on a substrate according to the disclosure.

DETAILED DESCRIPTION OF THE INVENTION

For a better understanding of the invention like parts in the drawings are denoted with like reference numerals.

Figures 1 and 2 show different embodiments of a bond testing apparatus according to the disclosure, which bond testing apparatus is denoted with reference numeral 100 in Figure 1 and reference numeral 200 in Figure 2.

The invention relates to a bond testing apparatus, in particular for determining a strength of a bond and/or a material present on a substrate.

As outlined in the introduction above, electrical connections in semiconductor and electronic assemblies often include bonds and it is known that these need to be mechanically tested as a means of measuring their quality. One such test is known as a shear test which can be performed with a bond testing apparatus. For performing such test, a part of the bond tester known as a shear tool loads the bond or material mounted on the substrate to either a specific load or until a failure of some type occurs. During this shearing or bond testing the force in the shear direction more or less parallel to the plane defined by the substrate is measured. After shear test is performed, the sheared surface is also visually inspected. In both Figure 1 and Figure 2 reference numeral 1 denotes such substrate. On a contact surface 1a of the substrate 1 multiple electric features, such as copper conductors, copper pillars, or solder balls 2a and/or electronic packages or electronic components 2b (such as resistors, capacitors, semiconductor ICs, etc. etc.) can be mounted and their bond tested as previously described. The substrate 1 can be of different types, including but not limited to FR4 or ceramic circuit boards, silicon chips and silicon wafers.

Returning to Figure 1 as well as Figure 2 the corresponding parts of both schematic representations of bond testing apparatus 100 and 200 according to the disclosure are explained. Both examples 100 and 200 are capable of determining the strength of such bond or ball 2a and/or a component 2b present on the substrate 1. The bond testing apparatus 100 (200) can be of a force measurement system type, and is composed of at least a frame housing 10. A shear tool component 20 as well as a shear height setting unit 30 are both accommodated in the frame housing 10.

The shear tool component 20 comprises a shear tool holder 21 which holds a shear tool 22. The shear tool 22 can be permanently mounted in the shear tool holder 21 , or can be of the replaceable type. The shear tool 22 has an elongated configuration, which ends in a free, shear tool tip 22a. For a proper operation of either embodiment 100 and 200, the shear tool component 20 is arranged for applying a shear force to the bond 2a and/or the material component 2b in a direction parallel to the plane defined by the substrate 1. This direction parallel to the plane defined by the substrate 1 is denoted with the arrow placed under the substrate 1 and pointing towards the left.

In this particular example, the shear tool component 20 may be mounted to the frame housing 10 by means of a shear tool sensor unit 11 , in which shear tool holder 21 contains the sensor for sensing or measuring the force, which is exerted by the shear tool 22 on a bond 2a or component 2b in the shear direction more or less parallel to the plane defined by the substrate 1.

According to the disclosure shown in Figure 1, the shear height setting unit

30 comprises a sensor element 31. The sensor element 31 is mounted between the shear tool sensor unit 11 and the frame housing 10. In various configuration, the sensor element

31 is one chosen from a group of a capacitive distance sensor element, an optical distance sensor element or a linear variable displacement transducer element.

The configurations of both embodiments depicted in Figure 1 and Figure 2 serve to establish an accurate position of the tip 22a of the shear tool 22 relative to the surface 1a of the substrate and in particular relative to the location of the bond 2a or component 2b present on the substrate 1. The accuracy of the positional alignment of the (tip 22a of the) shear tool 22 with reference to the location of the bond 2a or component 2b present on the substrate 1 is known to be of great importance.

With both embodiments an accurate alignment of the tip 22a of the shear tool 22 relative to the surface 1a, also known as the “shear height”, can be established. The “shear height” is the distance between (the tip 22a of the shear tool 22 and the surface 1a of the substrate 1 next to the bond 2a or material component 2b under test, seen in the z-direction normal to the surface of the substrate. In Figure 1 and 2 the “shear height” is denoted with ‘x’. Setting the height alignment ‘x’ in an accurate manner and maintaining that height alignment during the shear test is important for performing an accurate bond test

Hereto, during a first operational condition of the bond testing apparatus 100 (or 200), the complete unit, being the frame housing 10 including the shear tool component 20, the shear tool sensor unit 11 as well as the shear height setting unit 30 can be displaced in a direction normal to the plane defined by (the contact surface 1a of) the substrate 1 by means of a displacement unit (not depicted). The direction normal to the plane is denoted with the vertical oriented double arrow left of the frame housing 10 of both examples 100 and 200.

With the sensor element 31 it is possible to accurately determine the moment the shear tool component 20, and in particular the tip 22a of the shear tool 22 ‘touches’ the substrate surface 1a. During the first operational condition of moving the shear tool component 20 (and the frame housing 10) in the z-direction towards the substrate 1, the tip 22a of the shear tool 22 touches the substrate surface 1a, a difference in distance between the shear tool sensor unit 11 and the sensor element 31 is being sensed. Once “touchdown” is sensed the displacement in a z-direction normal to the substrate is ceased and the “touchdown” of the tip 22a touching the surface 1a sets a reference position, which is used to set - during a second operation condition of the bond testing apparatus 100 - the desired shear height ‘x’, that is the desired height of the tip 22a relative to the substrate surface 1a for performing the shear test on either a bond 2a or an component 2b.

Hereto, the shear height setting unit 30 comprises a height actuator unit, a first embodiment thereof being depicted in Figure 1 and denoted with reference numeral 32. The height actuator unit 32 of Figure 1 is mounted between the shear tool sensor unit 11 and the frame housing 10, seen in the direction normal to the plane formed by the substrate 1. The height actuator unit is arranged, during the second operation condition of the bond testing apparatus 100, in moving the shear tool component 20 relative to the frame housing 10 in a direction away from the substrate 1, hence in a direction opposite to the z-direction of ‘touchdown’ movement of the shear tool component 20 during the first operational condition.

During the second operation condition the frame housing 10, which has been displaced previously during the first operational condition together with the shear tool component 20 in the z-direction towards the substrate 1, is set in a fixed position relative to the substrate 1 , and only the shear tool component 20 is moved relative to the frame housing 10 in a direction away from the substrate 1, hence in a direction opposite to the z-direction of ‘touchdown’ movement. Thus, a limited amount of mass of the shear tool component 20 is displaced, and because all these movements are done locally a very high accuracy can be obtained. Because of the limited mass displacement of only the shear tool component 20 and the shear tool tip 21, the bond test apparatus 100 can be operated very accurately and allow shear height settings in the submicron range.

As the height actuator unit 30 only needs to displace the shear tool component 20 relative to the frame housing 10 in a direction away from the substrate 1, the overall mass displacement is limited and also a limited number of parts are involved. Accordingly, when performing the shear test, the stiffness of the construction in shear direction can be very high thus ascertaining an improved accuracy in the shear height setting, in particular in the submicron range.

In particular, the height actuator unit 30 may comprise a piezoelectric actuator element 32 as well as an electromagnet connecting (or clamp) unit 33. The electromagnet connecting (or clamp) unit 33 serves to mechanically connect or clamp, during the second operational condition, the piezoelectric actuator element 32 with the shear tool component 20, and more in particular to mechanically connect or clamp the piezoelectric actuator element 32 with the shear tool sensor unit 11.

The mechanical connection or clamping between the piezoelectric actuator element 32 with the shear tool component 20, in particular with the shear tool sensor unit 11 is achieved by means of a magnetic clamping force exerted between both parts 32 and 20/11. In particular, the shear tool component 20 comprises a contact flange element 34 made of a magnetic material. The contact flange element 34 made of a magnetic material is permanently mounted to the shear tool component 20 and in particular with the shear tool sensor unit 11 with its contact surface element 34a.

During the first operational condition of the bond testing apparatus 100, the contact flange element 34 will just graze the electromagnet connecting unit 33, during which the electromagnet connecting unit 33 is de-activated. In the second operational condition, the electromagnet connecting unit 33 will be activated and the contact flange element 34, the shear tool sensor unit 11 and the shear tool component 20 will be mechanically coupled to the electromagnet connecting unit 33 and the piezoelectric actuator element 32 by means of the magnetic force induced by the activated electromagnet of the electromagnet connecting unit 33.

This mechanical interconnection due to magnetic force, allows the piezoelectric actuator element 32 to accurately displace the shear tool component 20 and hence the shear tool 22 in an up and down direction normal to the plane of the substrate 1 and accordingly lift the shear tool component 20 (and shear tool 22) to the required shear height ‘x’.

In short, the shear height setting unit 30 is arranged to determine, during the first operational condition of the displacement unit displacing the frame housing 10 in a direction towards the substrate 1 , when the shear tool component 20 and the tip 22a of the shear tool 22 comes in contact with the upper surface 1a of the substrate 1. The contact position or touchdown sets a contact height or reference position. During the second operational condition wherein the displacement unit is not displacing the frame housing 10, the electromagnet connecting unit 33 of the shear height setting unit 30 is activated, thus clamping the shear tool component 20 with the height actuator unit 32, and the shear tool component 20 can be displaced relative to the frame housing 10 and in a direction away from the substrate 1 in order to set a shear height ‘x’ of the shear tool component relative to the contact height or reference position.

The operation of the bond testing apparatus 100, both during the first and second operational condition, is controlled by means of a control unit 35, which can be accommodated in the frame housing 10 or mounted externally, outside the housing 10. The control unit 35 operates the displacement unit for displacing the frame housing 10 towards and away the substrate 1 , receives the signals generated by the sensor element 31 determining and establishing the ‘touchdown’ reference position, generates signals for activating and de-activing the electromagnet claiming unit 33, as well as for controlling the height actuator unit 32 for lifting the shear tool component 20 and shear tool 22 to the required shear height ‘x’.

Accordingly, the shear height ‘x’ can be set far more accurately compared to prior art bond test configurations. With this example depicted in Figure 1 , only the shear tool component 20 is being displaced relative to the frame housing 10 and the substrate 1 for setting the shear height ‘x’. Thus, a limited amount of mass is being displaced, and because all these movements are done locally a very high accuracy can be obtained. Because of the limited mass displacement and local movement, the bond test apparatus according to the example of Figure 1 can be operated very accurately and allows shear height settings in the submicron range.

In yet another second example of a bond testing apparatus 200 is described in Figure 2. Its functionality and operation as to the first and second operational condition is quite similar as with the first example depicted in Figure 1.

Similarly, during the first operational condition of the bond testing apparatus 200), the complete unit, being the frame housing 10 including the shear tool component 20, the shear tool sensor unit 11 as well as the shear height setting unit 30 can be displaced in a direction normal to the plane defined by (the contact surface 1a of) the substrate 1 by means of a displacement unit (not depicted). The direction normal to the plane is denoted with the vertical oriented double arrow left of the frame housing 10.

The sensor element 31 allows for accurately determine the moment the shear tool component 20, and in particular the tip 22a of the shear tool 22 ‘touches’ the substrate surface 1a. The moment, during the first operational condition of moving the shear tool component 20 (and the frame housing 10) towards the substrate 1 , the tip 22a of the shear tool 22 touches the substrate surface 1a, a difference in distance between the shear tool sensor unit 11 and the sensor element 31 is being sensed.

Once “touchdown” is sensed the displacement in a z-direction normal to the substrate is ceased and the “touchdown” of the tip 22a touching the surface 1a sets a reference position, which is used to set - during a second operation condition of the bond testing apparatus 200 - the desired shear height ‘x’, that is the desired height of the tip 22a relative to the substrate surface 1a for performing the shear test on either a bond 2a or an component 2b.

In this second example, the shear height setting unit 30 comprises a height actuator unit denoted with reference numeral 44. The second embodiment of the height actuator unit 44 is mounted between the shear tool sensor unit 11 and the frame housing 10, seen in the direction normal to the plane formed by the substrate 1. The height actuator unit 44 is arranged, during the second operation condition of the bond testing apparatus 200, in moving the shear tool component 20 relative to the frame housing 10 in a direction away from the substrate 1, hence in a direction opposite to the direction of ‘touchdown’ movement of the shear tool component 20 during the first operational condition.

According to the second example, the height actuator unit 44 comprises a motor, preferably but not limited to a voice coil actuator element 44. This example of the height actuator unit 44 allows in a similar manner as in the first example of Figure 1 to accurately displace up and down and lift the shear tool component 20 to the required shear height ‘x’.

In both first and second examples, a control unit 35 is accommodated in the frame housing 10 and serves to operate the displacement unit for displacing the frame housing 10 towards and away the substrate 1 , receives the signals generated by the sensor element 31 determining and establishing the ‘touchdown’ reference position, generates signals for activating and de-activing the electromagnet claiming unit 33, as well as for controlling either height actuator unit 32/44 for lifting the shear tool component 20 and shear tool 22 to the required shear height ‘x’.

In both embodiments 100 and 200, during the second operation condition the frame housing 10, which has been displaced previously during the first operational condition together with the shear tool component 20 in the z-direction towards the substrate 1 , is set in a fixed position relative to the substrate 1. The shear tool component 20 is moved relative to the frame housing 10 in a direction away from the substrate 1, hence in a direction opposite to the z-direction of ‘touchdown’ movement, using either height actuator unit 32 and 44 of the first or second embodiment.

A limited amount of mass of the shear tool component 20 is displaced, and because all these movements are done locally a very high accuracy can be obtained. Because of the limited mass displacement of only the shear tool component 20 and the shear tool tip 22a, the bond test apparatus 100 and 200 can be operated very accurately and allow shear height settings in the submicron range.

Accordingly, the shear height ‘x’ can be set far more accurately compared to prior art bond test configurations. With the examples depicted in Figure 1 and 2, only the shear tool component 20 is being displaced relative to the frame housing 10 and the substrate 1 for setting the shear height ‘x’. Thus, a limited amount of mass is being displaced, and because all these movements are done locally a very high accuracy can be obtained. Because of the limited mass displacement and local movement, the bond test apparatus according to the examples can be operated very accurately and allows shear height settings in the submicron range.

In particular the control unit 35 of apparatus 100 is arranged to apply - during the first operational condition - a decreasing alternating current to the then deactivated electromagnet connecting unit 33 in order to reduce remnant magnetism present in the electromagnetic connecting unit 33 to a required amount. Any remnant magnetism will induce a small attracting force on the contact flange element 34 made of a (ferro)magnetic material causing unwanted some friction between the shear tool component 20 (shear tool sensor unit 11) and the height actuator unit 30. The remnant magnetic force can be beneficial in ensuring the contact flange element 34 remains in contact with the electromagnet connecting unit 33 but with a controlled amount of contact friction.

REFERENCE NUMERALS USED IN THE FIGURES

1 substrate

I a contact surface of substrate

2a electric bond or solder ball

2b electronic component x shear height

100 first example of bond testing apparatus

200 second example of bond testing apparatus

10 frame housing

I I shear tool sensor unit

12 shear tool sensor

20 shear tool component

21 shear tool holder

22 shear tool

22a shear tool tip

30 shear height setting unit

31 sensor element

32 first example of height actuator unit

33 electromagnet clamp unit

34 contact element

34a contact surface element

35 control unit

44 second example of height actuator unit