DEVICE AND METHOD FOR DETECTING A DEFECTIVE SOLDER CONTACT

Description

[0001] The invention relates to a device and a corresponding method for detecting a defect in a solder contact, in particular a solder bead, of a BGA (Ball Grid Array) component.

[0002] An electronic and / or electrical device may comprise a printed circuit board with one or more BGA components. A BGA component is electrically connected to corresponding electrical contacts on the printed circuit board via a plurality, in particular via a matrix, of solder contacts (in particular solder balls).

[0003] During operation of the device, one or more solder contacts of a BGA component may become defective, for example due to mechanical stress, which may impair the function of the device. To identify the one or more defective solder contacts, a relatively complex functional test of the device can be carried out. This can provide information about which one or more solder contacts are defective. Alternatively or in addition, a relatively complex cross-section through the sphere matrix can be produced and evaluated. Alternatively or in addition, a special test component can be arranged on the circuit board instead of the actual BGA component in order to monitor the wear of the solder contacts due to mechanical stress.

[0004] OBRZUT JAN: "Interconnection continuity test for packaged functional modules", THE 1998 INTERNATIONAL CONFERENCE ON CHARACTERIZATION AND METROLOGY FOR ULSI TECHNOLOGY, (1998-03-27), pages 607-609, describes a method for testing connections of an ESD-protected electronic module. US 2008 / 0144243 A1 describes a method for detecting defects in solder contacts. Voltlog: "Best Technique For Soldering & Inspecting BGA ChipsVoltlog #352", (2021-02-24). URL: https: / / www.youtube.com / watch?v=15RFI9wKHq8 is a video demonstrating a test procedure for testing a BGA component. KR 101 024 074 B1 describes a test procedure for a multi-chip assembly.

[0005] Locating a defective solder contact is therefore typically associated with a relatively high level of effort. This document addresses the technical task of enabling efficient, reliable, and non-destructive localization of a defective solder contact on a BGA component.

[0006] The object is achieved by the subject matter of the independent patent claims. Advantageous embodiments are defined in particular in the dependent patent claims, described in the following description, or illustrated in the accompanying drawings.

[0007] According to one aspect of the invention, a test device for testing a solder contact (in particular a solder ball) of a Ball Grid Array (BGA) component is described. The solder contact can be referred to as the "ball" of the BGA component. The BGA component can be arranged on a printed circuit board. The solder contact can be electrically connected to a corresponding contact of the printed circuit board. The BGA component can have an arrangement, in particular a matrix, of solder contacts. For example, the BGA component can have NxM solder contacts, e.g., with N and / or M greater than 2, or greater than 4, or greater than 10. The test device is configured to test several, in particular all, solder contacts of the BGA component. The test can be performed during operation of the BGA component within an electrical and / or electronic device (e.g., within a household appliance).

[0008] The solder contact to be tested is connected to a reference potential via an internal diode of the BGA component. The reference potential can be ground or the operating voltage (e.g., 12V or less, or 5V or less) of the BGA component. In particular, the plurality of solder contacts is each connected to the reference potential via an internal diode. Furthermore, the BGA component has at least one reference solder contact that is designed to (directly) connect the BGA component to the reference potential. In particular, the BGA component can have a first reference solder contact that connects the BGA component (directly) to a first reference potential (e.g., ground). Furthermore, the BGA component can have a second reference solder contact that connects the BGA component (directly) to a second reference potential (e.g., the operating voltage).

[0009] The multiple solder contacts of the BGA component can thus each be electrically coupled to at least one reference potential via at least one (blocking) internal diode. The internal diode can be provided as overvoltage protection (with respect to ESD, electrostatic discharge). The respective internal diode can be blocking when the voltage potential at the solder contact lies between the first reference potential (in particular ground) and the second reference potential (in particular the operating voltage). On the other hand, at least one of the internal diodes can become conductive when the voltage potential at the solder contact lies above the second reference potential or below the first reference potential.

[0010] The test device is configured to determine a measured value of the electrical resistance of the connection path from a measuring point via the solder contact to be tested and via the internal diode (of the solder contact to be tested) to the reference potential. The test device can, in particular, be configured to determine the measured value of the resistance during operation of the BGA component within an electrical and / or electronic device. Thus, the condition of the solder contact to be tested can be checked during operation of the BGA component.

[0011] Furthermore, the test device is configured to determine, based on the measured value, whether the solder contact to be checked has a defect or not. The test device can in particular be configured to determine whether the determined measured value of the resistance is greater than or less than a predefined resistance threshold. The resistance threshold can be, for example, greater than 1 kΩ and / or less than 10 MΩ. It can then be determined based on the comparison whether the solder contact to be checked has a defect or not. In particular, it can be determined that the solder contact to be checked has a defect if it is determined that the measured value of the resistance is greater than the resistance threshold. On the other hand, it can be determined that the solder contact to be checked does not have a defect if it is determined that the measured value of the resistance is less than the resistance threshold.

[0012] The test device can be configured to determine the resistance threshold (for the solder contact to be tested) in advance. For example, a measured electrical resistance value for an intact solder contact can be determined and used as a reference value. To test the solder contact (e.g., during operation of the BGA component), the reference value or a value derived from it can then be used as the resistance threshold. This allows a defect in a solder contact to be detected particularly reliably.

[0013] Thus, a test device is described that is designed to use the internal (connection) diode of a solder contact to check the condition of the solder contact (which, for example, has the function of overvoltage protection). This allows a defective solder contact to be detected efficiently and reliably.

[0014] As already explained above, the BGA component includes a reference solder contact, which is connected, in particular directly, to the reference potential (outside the BGA component). The connection path can then extend from the measurement point via the solder contact to be tested, via the internal diode, and via the reference solder contact to the reference potential. By using a reference solder contact, the connection of the reference potential to the BGA component can be achieved efficiently.

[0015] The test device is configured to determine reference information regarding whether the reference solder contact is defective or not. Taking the reference information into account, it is then determined in a particularly reliable manner whether the solder contact to be tested is defective or not. In particular, when evaluating the measured value, whether the reference solder contact is defective or not is taken into account. This further increases the reliability of detecting a defective solder contact.

[0016] The solder contact to be tested can be connected to the first reference potential, in particular to ground, via the internal diode of the BGA component, or to the second reference potential, in particular to the operating voltage of the BGA component. The test device can be configured to determine a first measured value of the electrical resistance of a first connection path from the measuring point via the solder contact to be tested to the first reference potential. Furthermore, a second measured value of the electrical resistance of a second connection path from the measuring point via the solder contact to be tested to the second reference potential can be determined. For this purpose, specific voltage potentials can be applied to the measuring point. To determine the first measured value, for example, a first voltage potential can be applied to the measuring point, which causes the diode to become conductive relative to the first reference potential.On the other hand, to determine the second measured value, a second voltage potential can be applied to the measuring point, causing the diode to become conductive relative to the second reference potential.

[0017] It can then be determined in a particularly reliable manner, based on the first measured value and on the second measured value, whether the solder contact to be tested has a defect or not. The test device can be configured, in particular, to determine that the solder contact to be tested has a defect if the first measured value and the second measured value are each greater than the resistance threshold. Furthermore, the test device can be configured to determine that the solder contact to be tested does not have a defect if the first measured value or the second measured value (i.e., at least one of the measured values) is less than the resistance threshold.

[0018] As already explained, the BGA component typically comprises a plurality of solder contacts (arranged, for example, in a matrix). The solder contacts can each be connected to the reference potential via a (possibly dedicated) internal diode of the BGA component.

[0019] The test device is configured to determine a plurality of measured values of the electrical resistance of a corresponding plurality of connecting paths. The connecting path for a solder contact to be tested runs from a respective measuring point, via the respective solder contact to be tested, and via the respective internal diode to the reference potential. Thus, measured values of the electrical resistance of the respective connecting path to the reference potential can be determined for the different solder contacts at the respective measuring points.

[0020] It can then be determined in a particularly precise manner on the basis of the plurality of measured values whether one or more of the plurality of solder contacts, in particular which one or more of the plurality of solder contacts, have a defect.

[0021] The test device is further configured to determine, based on the plurality of measured values, reference information as to whether the reference solder contact (to which the reference potential is connected) has a defect or not. The test device can, in particular, be configured to determine, based on the plurality of measured values as reference information, that the reference solder contact is defective if all of the plurality of measured values are greater than the resistance threshold. Furthermore, the test device can be configured to determine, based on the plurality of measured values as reference information, that the reference solder contact is not defective if at least one of the plurality of measured values is less than the resistance threshold. Thus, the reference information relating to the reference solder contact can be determined in a particularly efficient and reliable manner.

[0022] The internal diode between a solder contact to be tested and the reference potential can, if necessary, be operated in reverse direction during normal operation of the BGA component. The test device can be configured to apply a voltage potential to the measuring point (for testing the respective solder contact) in order to cause the internal diode on the connecting path from the measuring point via the solder contact to be tested and via the internal diode to the reference potential to be operated in forward direction during a test operation for determining the measured value of the resistance. This allows a measured value for testing a solder contact to be provided in a particularly reliable manner.

[0023] According to a further aspect, a method for testing a solder contact (in particular a solder bead or a "ball") of a BGA component is described. The BGA component is arranged on a circuit board and, if appropriate, with the circuit board within an electrical and / or electronic device (in particular within a household appliance). The solder contact to be tested is connected to a reference potential (e.g., to ground or to the operating voltage) via an internal diode of the BGA component.

[0024] The method involves determining a measured value of the electrical resistance of the connection path from a measuring point (to which a specific voltage potential is applied) via the solder contact to be tested and via the internal diode to the reference potential. To determine the measured value of the electrical resistance, a voltage potential can be applied to the measuring point, which, if the solder contact is intact, causes the internal diode to operate in the forward direction.

[0025] Furthermore, the method comprises determining, on the basis of the plurality of measured values, reference information as to whether the reference solder contact (222) has a defect or not; and determining (302), on the basis of the plurality of measured values and taking into account the reference information, whether one or more of the plurality of solder contacts (121, 223) have a defect.

[0026] It should be noted that any aspects of the device and method described in this document can be combined in a variety of ways. In particular, the features of the patent claims can be combined in a variety of ways.

[0027] The invention will be described in more detail below with reference to exemplary embodiments shown in the accompanying drawings. Figures 1a and 1b different views of a circuit board with a BGA component; Figure 2a an example solder contact; Figure 2b an example test device for checking a solder contact; Figure 2c an exemplary test device for locating a defective solder contact of a BGA component; and Figure 3 a flowchart of an exemplary method for locating a defective solder contact of a BGA component.

[0028] As stated at the beginning, this document deals with the efficient and reliable localization of a defective solder contact of a BGA component. In this context, the Figures 1a and 1b a printed circuit board 100 of an electrical and / or electronic device, which is equipped with a BGA component 110. The BGA component 110 is electrically connected to a corresponding arrangement of contact points of the printed circuit board 100 via an arrangement 120, in particular via a matrix, of solder contacts. The individual solder contacts can be electrically and mechanically connected to the corresponding contact points via solder. In particular, the individual solder contacts can each comprise solder, which can be used for soldering to the corresponding contact points. The individual solder contacts can be designed, for example, as solder balls or solder beads.

[0029] During operation of the device in which the printed circuit board 100 is arranged, an electrically conductive connection between a solder contact and a corresponding contact point may be impaired, e.g. due to mechanical stress. For example, a crack may form at the solder joint between a solder contact and the corresponding contact point. The solder joint may break. The impairment of a connection between a solder contact and a corresponding contact point may result in the functionality of the device being impaired. This document describes a device and a corresponding method that enable efficient and reliable localization of a defective solder contact (i.e. also a defective connection between a solder contact and a corresponding contact point on a printed circuit board 100).

[0030] Fig. 2ashows an exemplary solder contact 121 of a BGA component 110. The solder contact 121 is electrically conductively connected to one or more functional circuit elements within the BGA component 110 (represented by the triangle in Fig. 2a ). In addition, the solder contact 121 is typically connected to ground via a (connection) diode 111 or to the operating voltage (VCC) of the BGA component 110 via a (connection) diode 111. The diode 111 is arranged in the reverse direction, so that the solder contact 121 is coupled to ground via a blocking diode 111 or to the operating voltage via a blocking diode 111.

[0031] Fig. 2b shows an exemplary test device 200 for testing a solder contact 121. The solder contact 121 is Fig. 2b represented by a corresponding contact resistance 221. Furthermore, Fig. 2bhow the solder contact 121 (with the corresponding contact resistance 221) is coupled to ground or to the operating voltage (VCC) via a (connection) diode 111 and a line resistance 211.

[0032] The test device 200 can be configured to determine a measured value of the electrical and / or ohmic resistance of the connection path from the measuring point 201, via the solder contact 121 and via a (connection) diode 111, to ground or to the operating voltage. In this case, the test device 200 can be configured to cause the diode 111 to be in the forward direction for measuring the resistance. This can be achieved by appropriately adjusting the voltage potential at the measuring point 201. By operating the (connection) diode 111 in the forward direction, it can be ensured that the measured value of the resistance should be relatively low (e.g., less than 1 kΩ) when an intact solder contact 121 is present. On the other hand, a relatively high measured value of the resistance (e.g., equal to or greater than 1 MΩ) indicates a defective solder contact 121.

[0033] Fig. 2cshows an exemplary arrangement 120 of solder contacts 121, 222, 223. In the example shown, the (first) solder contact 223 to be tested is connected via a diode 111 to the reference solder contact 222 connected to ground. The test device 200 is configured to record the measured value of the resistance of the connecting path between the measuring point 201 and ground. For this purpose, a voltage potential can be applied to the measuring point 201, causing the diode 111 to become conductive. The connecting path comprises the first solder contact 223, the (forward-biased) diode 111, and the reference solder contact 222. Based on the measured value of the resistance of this connecting path, it can be checked whether the first and / or the reference solder contact 223, 222 have a defect.

[0034] In a corresponding manner, a measured value of the resistance can be determined for each of a plurality of (first) solder contacts 223 to be tested. Thus, for a plurality of different (first) solder contacts 223, a measured value of the resistance of the connecting path from the measuring point 201 via the respective (first) solder contact 223, via the uniform reference solder contact 222 to ground can be determined. The reference solder contact 222 is designed to generally connect the BGA component 110 to a reference potential (e.g., ground or the operating voltage).

[0035] From the multitude of measured values of the resistance of the respective connection section, the following can be concluded: If all measured values are equal to or greater than the predefined resistance threshold (e.g., 1 MΩ), then it can be concluded that the uniform reference solder contact 222 has a defect; if at least one measured value is less than the resistance threshold, then it can be concluded that the reference solder contact 222 does not have a defect; and / or if one or more measured values (but not all measured values) are equal to or greater than the resistance threshold, then it can be concluded that the solder contact 223 to be tested with the respective measured value has a defect.

[0036] As explained above, all solder contacts 121, 222, 223 of a BGA component 110 should have an electrically conductive contact with the circuit board 100 via respective solder joints in order to ensure the full functionality of the BGA component 110. However, it may happen that a solder joint cracks, thus making an electrical connection no longer possible.

[0037] In order to monitor the electrical connection during a test of a printed circuit board 100 or directly in a device, the electrical resistance of the diode 111 in the BGA component 110 can be measured via a BGA solder joint 223 under test to ground or to VCC. If a high-resistance measurement occurs on the ohmmeter 200 (i.e., on the test device), it can be concluded that the BGA solder joint 223 under test is cracked. Using the method described in this document, BGA components 110 can be characterized during testing and / or a specific failure time can be determined during operation. Furthermore, a BGA component 110 can be monitored continuously or repeatedly during operation in a device.

[0038] Fig. 3shows a flowchart of a (possibly computer-implemented) method 300 for testing a solder contact 121, 223 (in particular, a solder bead or a "ball") of a BGA component 110. The solder contact 121, 223 to be tested is connected to a reference potential (e.g., ground or the operating voltage VCC) via an internal diode 111 of the BGA component 110. The internal diode 111 can be off during normal operation.

[0039] The method 300 comprises determining 301 a measured value of the electrical resistance of the connection path from a measuring point 201 via the solder contact 121, 223 to be tested and via the internal diode 111 to the reference potential. For this purpose, a voltage potential can be applied to the measuring point 201, causing the internal diode 111 to be operated in the forward direction.

[0040] The method 300 further includes determining 302, based on the measured value, whether the solder contact 121, 223 to be inspected has a defect or not. A measured value that is greater than a specific resistance threshold may be an indication of a defective solder contact 121, 223. On the other hand, a measured value that is less than the specific resistance threshold may be an indication of a defect-free solder contact 121, 223.

[0041] The measures described in this document allow the solder contacts 121, 222, 223 of a BGA component 110 to be tested and / or monitored efficiently and reliably. This can increase the reliability of a printed circuit board 100 with a BGA component 110.

[0042] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and figures are intended only to illustrate the principle of the proposed device and method.

Claims

1. System comprising, - a ball grid array, BGA, component (110) arranged on a circuit board (100); wherein the BGA component (110) comprises a reference solder contact (222) which is connected to a reference potential; wherein the BGA component (110) comprises a plurality of solder contacts (121, 223); wherein the solder contacts (121, 223) are connected to the reference potential in each case via an internal diode (111) of the BGA component (110) and via the reference solder contact (222); and - a test apparatus (200) for checking a solder contact (121, 223) of the BGA component (110); wherein the test apparatus (200) is designed, - to determine a plurality of measured values of an electrical resistance of a corresponding plurality of connecting passages for the corresponding plurality of solder contacts (121, 223); wherein the connecting passages for a solder contact (121, 223) to be checked runs from a respective measuring point (201) to the reference potential via the solder contact (121, 223) to be checked in each case, via the respective internal diode (111) and via the reference solder contact (222); - to determine reference information on the basis of the plurality of measured values to ascertain whether the reference solder contact (222) has a defect or not; and - to ascertain on the basis of a plurality of measured values and taking account of the reference information whether one or more of the plurality of solder contacts (121, 223) have a defect.

2. System according to claim 1, wherein the test apparatus (200) is designed, - to determine whether the determined measured value of the resistance for a solder contact (121, 223) to be checked is greater than or lesser than a predefined resistance threshold value; and - to ascertain on this basis whether the solder contact (121, 223) to be checked has a defect or not.

3. System according to one of the preceding claims, wherein - a solder contact (121, 223) to be checked is connected via the internal diode (111) of the BGA component (110) to a first reference potential, in particular to earth, or to a second reference potential, in particular to an operating voltage of the BGA component; and - the test apparatus (200) is designed, - to determine a first measured value of the electrical resistance of a first connecting passage from the respective measuring point (201) to the first reference potential via the solder contact (121, 223) to be checked; - to determine a second measured value of the electrical resistance of a second connecting passage from the respective measuring point (201) to the second reference potential via the solder contact (121, 223) to be checked; and - to ascertain on the basis of the first measured value and on the basis of the second measured value whether the solder contact (121, 223) to be checked has a defect or not.

4. System according to claim 3, wherein the test apparatus (200) is designed, - to ascertain that the solder contact (121, 223) to be checked has no defect, when the first measured value or the second measured value are smaller than a resistance threshold value; and / or - to ascertain that the solder contact (121, 223) to be checked has a defect when the first measured value and the second measured value are each greater than the resistance threshold value.

5. System according to one of the preceding claims, wherein the test apparatus (200) is designed to ascertain on the basis of the plurality of measured values as reference information that - the reference solder contact (220) is defective when all measured values of the plurality of measured values are greater than a resistance threshold value; and / or - the reference solder contact (220) is not defective when at least one measured value of the plurality of measured values is lesser than the resistance threshold value.

6. System according to one of the preceding claims, wherein - the internal diode (111) between a solder contact (121, 223) to be checked and the reference potential is operated in the reverse direction in a normal mode of the BGA component (110); and - the test apparatus (200) is embodied to apply a voltage potential to the measuring point (201) in order to effect that the internal diode (111) on the connecting passage from the measuring point (201) to the reference potential via the solder contact (121, 223) to be checked and via the internal diode (111) is operated in the forward direction in a test mode for determining the measured value of the resistance.

7. System according to one of the preceding claims, wherein the test apparatus (200) is embodied to determine the measured value of the resistance during operation of the BGA component (110) within an electrical and / or electronic device.

8. Method (300) for checking a solder contact (121, 223) of a ball grid array, BGA, component (110) arranged on a circuit board (100); wherein the BGA component (110) comprises a reference solder contact (222) which is connected to a reference potential; wherein the BGA component (110) comprises a plurality of solder contacts (121, 223); wherein the solder contacts (121, 223) are each connected to the reference potential via an internal diode (111) of the BGA component (110) and via the reference solder contact (222); wherein the method (300) comprises, - determining (301) a plurality of measured values of an electrical resistance of a corresponding plurality of connecting passages for the corresponding plurality of solder contacts (121, 223); wherein the connecting passage for a solder contact (121, 223) to be checked runs from a respective measuring point (201) to the reference potential via the solder contact (121, 223) to be checked in each case, via the respective internal diode (111) and via the reference solder contact (222); - determining, on the basis of the plurality of measured values, reference information to ascertain whether the reference solder contact (222) has a defect or not; and - ascertaining (302) on the basis of the plurality of measured values and taking account of the reference information whether one or more of the plurality of solder contacts (121, 223) have a defect.