Process and circuit for testing a solder joint for faults

• US 6,404,206 B1
• Filed: 11/04/1999
• Issued: 06/11/2002
• Est. Priority Date: 05/05/1997
• Status: Expired due to Fees

• Current Assignee: Macroscience Technology GmbH (Schmidt Electronics Group Ltd.)
• Original Assignee: Ingram Micro Services GmbH (HNA Technology Co. Ltd.)
• Inventors: Sperschneider, Eckhard
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Hamdan, Wasseem H.
• Application Number:
  US09/433,954
• Time in Patent Office: 950 Days
• Field of Search: 324/500, 324/537, 324/750, 324/158.1, 702/57, 702/58, 702/82
• US Class Current: 324/537
• CPC Class Codes: G01N 23/04 and forming images of the material
• CPC Class Codes: G01N 23/083 the radiation being X-rays
• CPC Class Codes: G01N 23/18 Investigating the presence of flaws defects or foreign matter
• CPC Class Codes: G01R 31/304 of printed or hybrid circuits G01R31/305 - G01R31/315 take precedence
• CPC Class Codes: G01R 31/71 Testing of solder joints
• CPC Class Codes: H05K 13/082 Integration of non-optical monitoring devices, i.e. using non-optical inspection means, e.g. electrical means, mechanical means or X-rays

Abstract

In a process and apparatus for inspecting welding points (or solder joints) for defects by means of X-rays, before the welding points are inspected, the values of predeterminable measurement parameters, such as height of a welding meniscus or rise of a grey scale value curve generated by the device, are determined for reference welding points. When the welding points are subsequently inspected, selected measurement parameters are evaluated.

Claims

1. A process for selecting at least one measuring parameter for testing a solder joint (SJ) for freedom from faults by means of X-rays,

where the solder joint (SJ) is arranged on a substrate (BOARD),

where a fault-free solder joint (SJG) has solder material (SM),

where the solder material (SM) of said fault-free solder joint (SJG) is electrically connected to a contact element (PIN) of a component (CMP), and

where the solder joint (SJ) is assigned to a predefinable solder-joint type as a function of a shape of the contact element (PIN) in the region of the solder joint (SJ),

said process comprising the following steps:

before the solder joint (SJ) is tested, for each measuring parameter in a first number (m) of measuring parameters (PARi, i=1 . . . m) which characterize physical attributes of a solder joint, determining at least one of a lower range limiting value (LVDFAi) and an upper range limiting value (UVDFAi) of a fault actual-value range (DFAi) specific to a measuring parameter, a comparatively large fault in the solder joint (SJ) or a comparatively small fault in the solder joint (SJ) corresponding to the lower range limiting value (LVDFAi), a comparatively small fault in the solder joint (SJ) or a comparatively large fault in the solder joint (SJ) corresponding to the upper range limiting value (UVDFAi), the measuring parameters (PARi) in each case describing one of topography and internal structure of a second number (n) of fault-free reference solder joints (SJGREFj, j=1 . . . n), whereby at least one of m lower range limiting values (LVDFAi) and m upper range limiting values (UVDFAi) of fault actual-value ranges (DFAi) specific to a measuring parameter are determined;

before the solder joint (SJ) is tested, for each measuring parameter in the first number (m) of measuring parameters (PARi), ascertaining a measuring parameter value (PARiVALSJBREF) specific to a reference solder joint, for at least one faulty reference solder joint (SJBREF) of a type identical to the fault-free reference solder joint, so that at least m measuring parameter values (PARiVALSJBREF) specific to reference solder joints are ascertained for the m measuring parameters (PARi) for the at least one faulty reference solder joint (SJBREF);

before the solder joint (SJ) is tested, for each of the m measuring parameter values (PARiVALSJBREF), specific to a reference solder joint, of the faulty reference solder joints (SJBREF) determining its mathematical relationship, comprising one of a difference and a ratio, to one of the lower range limiting value (LVDFAi) and the upper range limiting value (UVDFAi) of the fault actual-value range (DFAi) specific to a measuring parameter;

during testing of a solder joint (SJ), identifying a measuring parameter value (PAR1VALSJ) of a first measuring parameter (PAR1) for which the measuring parameter value (PAR1VALSJBREF), specific to a reference solder joint, of the at least one faulty reference solder joint (SJBREF) is one of closest to and furthest from the lower range limiting value (LVDFA1) of the fault actual-value range (DFA1) specific to a measuring parameter, as compared with other fault actual-value ranges (DFA2, . . . , DFAm) specific to a measuring or for which the measuring parameter value (PAR1VALSJBREF), specific to a reference solder joint, of the at least one faulty reference solder joint (SJBREF) is one of furthest from and closest to the upper range limiting value (UVDFA1) of the fault actual-value range (DFA1) specific to a measuring parameter, as compared with fault actual-value ranges (DFA2, . . . , DFAm) specific to a measuring parameter.

2. The process according to claim 1, further comprising:

during testing of the solder joint (SJ), ascertaining at least one second measuring parameter value (PAR2VALSJ) of a second measuring parameter (PAR2) for which the measuring parameter value (PAR2VALSJBREF) specific to a reference solder joint of the at least one faulty reference solder joint (SJBREF) is one of second closest to and second furthest from the lower range limiting value (LVDFA2) of the fault actual-value range (DFA2) specific to a measuring parameter, as compared with fault actual-value ranges (DFA3, . . . , DFAm) for other measuring parameters, or for which the measuring parameter value (PAR2VALSJBREF) specific to a reference solder joint of the at least one faulty reference solder joint (SJBREF) is one of second furthest from and second closest to the upper range limiting value (UVDFA2) of the fault actual-value range (DFA2) specific to a measuring parameter, as compared with other fault actual-value ranges (DFA3, . . . , DFAm) specific to a measuring parameter.

3. The process according to claim 1, wherein:

before the solder joint (SJ) is tested, measuring parameter values (PARoVALSJBREF) of the first number (m) of measuring parameters (PARi) are ascertained for a third number (o) of faulty reference solder joints (SJBREFP, p=1 . . . o) of an identical type;

before the solder joint (SJ) is tested, at least one measuring parameter value (PARiVALAVESJBREF) of the faulty reference solder joints (SJBREF) is derived from the respective o measuring parameter values (PARoVALSJBREF), specific to a reference solder joint, of each measuring parameter (PARi) in accordance with a predefinable algorithm (AL1);

before the solder joint (SJ) is tested, instead of a mathematical relationship of the measuring parameter values (PARiVALSJBREF), for a reference solder joint of the faulty reference solder joints (SJBREF) of an identical type, to the lower range limiting value (LVDFAi) or the upper range limiting value (UVDFAi) of the respective fault actual-value range (DFAi) specific to a measuring parameter, a mathematical relationship of the derived measuring parameter values (PARiVALAVESJBREF), comprising one of a difference and a ratio, to the lower range limiting value (LVDFAi) or to the upper range limiting value (UVDFAi) of the respective fault actual-value range (DFAi) specific to a measuring parameter is determined; and

during testing of the solder joint (SJ), instead of the measuring parameter value (PAR1VALSJ), a further measuring parameter value (PARi′

VALSJ) of at least one further first measuring parameter (PARi′

) is ascertained, for which the derived measuring parameter value (PARiVALAVESJBREF) of the third number (o) of the faulty reference solder joints is one of closest to and furthest from the lower range limiting value (LVDFAi) of the fault actual-value range (DFAi), as compared with other fault actual-value ranges (DFA3, . . . DFAm) specific to a measuring parameter, or for which the derived measuring parameter value (PARiVALAVESJBREF) of the third number (o) of faulty reference solder joints one of furthest from and closest to the upper range limiting value (UVDFAi) of the fault actual-value range (DFAi), as compared with other fault actual-value ranges (DFA3, . . . , DFAm) specific to a measuring parameter.

4. The process according to claim 1, wherein one of the lower range limiting value (LVDFAi) and the upper range limiting value of the fault actual-value range (DFAi) specific to a measuring parameter is determined as a function of a measuring parameter value in which a faulty solder joint has an inadequate contact area between solder material and contact element (PIN).

5. The process according to claim 1, wherein one of the upper range limiting value (UVDFAi) and the lower range limiting value of the fault actual-value range (DFAi) for a measuring parameter is determined as a function of a distribution function of measuring parameter values (PARi) of the fault-free reference solder joints (SJREF).

6. The process according to claim 5, wherein:

the distribution function of measuring parameter values (PARi) of the fault-free reference solder joints is a normal distribution; and

one of the upper range limiting value (UVDFAi) and the lower range limiting value of the fault actual-value range (DFAi) specific to a measuring parameter is determined as a function of a standard deviation.

7. The process according to claim 1, wherein one of the upper range limiting value (UVDFAi) and the lower range limiting value of the fault actual-value range (DFAi) for a measuring parameter is fixed to a value which is slightly smaller or greater than the measuring parameter value of a still fault-free reference solder joint (SFGREF).

8. The process according to claim 1, wherein a solder joint (SJ) is judged to be fault-free during a testing if the measuring parameter value is one of at least as large and at most as small, as a predefinable, first threshold value (Ti1) for a measuring parameter.

9. The process according to claim 8, wherein the first threshold value (Ti1) for a measuring parameter is the same size as the upper range limiting value (UVDFAi) of the fault actual-value range (DFAi) for the measuring parameter.

10. The process according to claim 9, wherein a solder joint (SJ) is judged to be fault-free during testing if a measuring parameter value is at least as large as a predefinable, second threshold value (Ti2) specific to a measuring parameter, which threshold value differs, by a threshold value deviation (ia) specific to the measuring parameter, from the first threshold value (Ti1) specific to the measuring parameter.

11. The process according to claim 10, wherein one of the magnitude of a permissible threshold value deviation (a), specific to a measuring parameter, of a first measuring parameter, and the magnitudes of further permissible threshold value deviations (b, c), specific to a measuring parameter, of further measuring parameters is determined as a function of a predefinable reference value (CTAREF) of a mathematical combination of the threshold value deviations (a, b, c), comprising one of a product, an average and a sum of the threshold value deviations.

12. The process according to claim 10, wherein one of the magnitude of a permissible threshold value deviation (a), specific to a measuring parameter, of a first measuring parameter, and the magnitudes of further permissible threshold value deviations (b, c), specific to a measuring parameter, of further measuring parameters is determined as a function of a predefinable reference value (CTAREF) of a contact area (CTA) formed between the solder material (SM) and contact element (PIN) of a solder joint (SJ) to be tested.

13. The process according to claim 11, wherein

an item of information which designates the probability of the existence of an electrical contact between solder material (SM) and a contact element (PIN) is formed as a function of measuring parameter values of first measuring parameters;

and

the magnitude of the contact area (CTA) is determined based on measuring parameter values of second measuring parameters.

14. The process according to claim 13, wherein the magnitude of the contact area (CTA) is determined based on an item of information which designates at least one of a longitudinal extent (ml) of the solder joint (SJ, SJREF), a width extent (b) of the solder joint (SJ), a valley width (v) of a cross section of the solder joint (SJ), a first height difference (hp) between a vertex point (heel) and a valley point (pad) of the solder joint, a second height difference (phd) between the valley point (pad) of the solder joint (SJ) and the substrate (BOARD), a fall (neg) in an edge region of the solder joint (SJ), a rise (sl) in an edge region of the solder joint (SJ), and a quantity of material (d) in a predefinable region of the solder joint (SJ).

15. The process according to claim 1, wherein process steps carried out before the solder joint (SJ) are tested, are carried out with a time offset.

16. The process according to claim 1, wherein:

a result of the test, one of a first item of information (INFSJG) and a second item of information (INFSJB) is formed;

the first item of information (INFSJG) indicates freedom from faults of a tested, fault-free solder joint (SJ), and the second item of information (INFSJB) indicates the presence of faults of a tested, faulty solder joint (SJ); and

the first or second item of information is used to control a process for producing solder joints.

17. The process according to claim 1 wherein:

said measuring parameters comprise gray-value measuring parameters; and

said measuring parameter values comprise gray-value measuring parameter values.

21. A circuit arrangement (SJTD) for selecting at least one measuring parameter for a solder joint (SJ) for freedom from faults by means of X-rays, wherein:

the circuit arrangement has a data processing device (C) with an associated control program;

the solder joint (SJ) is arranged on a substrate (BOARD);

a fault-free solder joint (SJG) has solder material (SM);

the solder material (SM) of a fault-free solder joint (SJG) is connected electrically to a contact element (PIN) of a component (CMP);

the solder joint (SJ) is assigned to a predefinable solder-joint type as a function of a shape of the contact element (PIN) in a region of the solder joint (SJ); and

the control program embodies the Process according to one of the preceding claims.

35. The circuit arrangement according to claim 21, wherein the control program is configured such that process steps carried out before the solder joint (SJ) is tested are carried out with a time offset.

36. The circuit arrangement according to claim 21, wherein the control program is configured such that:

as a result of the test, one of a first item of information (INFSJG) and a second item of information is formed;

the first item of information (INFSJG) indicates freedom from faults of a tested, fault-free solder joint (SJ), and the second item of information (INFSJB) indicates the presence of faults of a tested, faulty solder joint (SJ); and

the first or second item of information is used to control a process for producing solder joints.

37. The circuit arrangement according to claim 21,

wherein the control program is configured to perform the following steps:

before the solder joint (SJ) is tested, for each measuring parameter in a first number (m) of measuring parameters (PARi, i=1 . . . m) which characterize physical attributes of a solder joint, determining at least one of a lower range limiting value (LVDFAi) and an upper range limiting value (UVDFAi) of a fault actual-value range (DFAi) specific to a measuring parameter, a comparatively large fault in the solder joint (SJ) or a comparatively small fault in the solder joint (SJ) corresponding to the lower range limiting value (LVDFAi), a comparatively small fault in the solder joint (SJ) or a comparatively large fault in the solder joint (SJ) corresponding to the upper range limiting value (UVDFAi), the measuring parameters (PARi) in each case describing one of topography and internal structure of a second number (n) of fault-free reference solder joints (SJGREFj, j=1 . . . n), whereby at least one of m lower range limiting values (LVDFAi) and m upper range limiting values (UVDFAi) of fault actual-value ranges (DFAi) specific to a measuring parameter are determined;

before the solder joint (SJ) is tested, for each measuring parameter the first number (m) of measuring parameters (PARi), ascertaining a measuring parameter value (PARiVALSJBREF) specific to a reference solder joint, for at least one faulty reference solder joint (SJBREF) of a type identical to the fault-free reference solder joint, so that at least m measuring parameter values (PARiVALSJBREF) specific to reference solder joints are ascertained for the m measuring parameters (PARi) for the at least one faulty reference solder joint (SJBREF);

before the solder joint (SJ) is tested, for each of the m measuring parameter values (PARiVALSJBREF), specific to a reference solder joint, of the faulty reference solder joints (SJBREF) determining its mathematical relationship, comprising one of a difference and a ratio, to one of the lower range limiting value (LVDFAi) and the upper range limiting value (UVDFAi) of the fault actual-value range (DFAi) for a measuring parameter;

during testing of solder joint (SJ), identifying a measuring parameter value (PAR1VALSJ) of a first measuring parameter (PAR1) for which the measuring parameter value (PAR1VALSJBREF), specific to a reference solder joint, of the at least one faulty reference solder joint (SJBREF) is one of closest to and furthest from the lower range limiting value (LVDFA1) of the fault actual-value range (DFA1) specific to a measuring parameter, as compared with other fault actual-value ranges (DFA2, . . . , DFAm) specific to a measuring parameter, or for which the measuring parameter value (PAR1VALSJBREF), specific to a reference solder joint, of the at least one faulty reference solder joint (SJBREF) is one of furthest from and closest to the upper range limiting value (UVDFA1) of the fault actual-value range (DFA1) specific to a measuring parameter, as compared with other fault actual-value ranges (DFA2, . . . , DFAm) specific to a measuring parameter.

38. The process according to claim 21 wherein:

said measuring parameters comprise gray-value measuring parameters; and

said measuring parameter values comprise gray-value measuring parameter values.

18. A process for testing a solder joint (SJ) for freedom from faults by means of X-rays,

where the solder joint (SJ) is arranged on a substrate (BOARD),

where solder material (SM) of a fault-free solder joint (SJ) is connected electrically to a contact element (PIN) of a component (CMP), and

where the solder joint (SJ) is assigned to a predefinable solder-joint type as a function of a shape of the contact element (PIN) in the region of the solder joint (SJ),

said process comprising:

testing the solder joint (SJ) to determine a magnitude of a contact area (CTA) formed between the solder material (SM) and contact element (PIN);

comparing the magnitude of the contact area (CTA) formed between the solder material (SM) and contact element (PIN) with a predefinable contact-area reference value (CTAREF); and

judging the solder joint (SJ) to be fault-free solder joint (SJG) or a faulty solder joint (SJB) as a function of a result of the comparison.

19. The process according to claim 18, wherein said testing step comprises:

generating an item of information which designates a probability of the existence of an electrical contact between the solder material (SM) and contact element (PIN) as a function of measuring parameter values of first measuring parameters (PM1); and

determining the magnitude of the contact area (CTA) as a function of measuring parameter values of second measuring parameters (PM2).

20. The process according to claim 19, wherein:

the first measuring parameter is a measuring parameter that designates at least one of a meniscus of a solder joint and solder material (SM) arranged laterally on the contact element (PIN); and

the second measuring parameter designates at least one of a longitudinal extent (ml) of the solder joint (SJ, SJREF), a width extent (b) of the solder joint (SJ), a valley width (v) of a cross section of the solder joint (SJ), a first height difference (hp) between a vertex point (heel) and a valley point (pad) of the solder joint, a second height difference (phd) between the valley point (pad) of the solder joint (SJ) and the substrate (BOARD), a fall (neg) in an edge region of the solder joint (SJ), a rise (sl) in an edge region of the solder joint (SJ), and a quantity of material (d) in a predefinable region of the solder joint (SJ).

22. The circuit arrangement according to claim 20, wherein the control program is further configured such that:

during testing of the solder joint (SJ), ascertaining at least one second measuring parameter value (PAR2VALSJ) of a second measuring parameter (PAR2) for which the measuring parameter value (PAR2VALSJBREF) specific to a reference solder joint of the at least one faulty reference solder joint (SJBREF) is one of second closest to and second furthest from the lower range limiting value (LVDFA2) of the fault actual-value range (DFA2) specific to a measuring parameter, as compared with other fault actual-value ranges (DFA3, . . . , DFAm) specific to a measuring parameters, or for which the measuring parameter value (PAR2VALSJBREF) specific to a reference solder joint of the at least one faulty reference solder joint (SJBREF) is one of second furthest from and second closest to the upper range limiting value (UVDFA2) of the fault actual-value range (DFA2) specific to a measuring parameter, as compared with other fault actual-value ranges (DFA3, . . . , DFAm) specific to a measuring parameter.

23. The circuit arrangement according to claim 20, wherein the control program is configured such that:

before the solder joint (SJ) is tested, measuring parameter values (PARoVALSJBREF) of the first number (m) of measuring parameters (PARi) are ascertained for a third number (o) of faulty reference solder joints (SJBREFP, p=1 . . . o) of an identical type;

before the solder joint (SJ) is tested, at least one measuring parameter value (PARiVALAVESJBREF) of the faulty reference solder joints (SJBREF) is derived from the respective o measuring parameter values (PARoVALSJBREF), specific to a reference solder joint, of each measuring parameter (PARi) in accordance with a predefinable algorithm (AL1);

before the solder joint (SJ) is tested, instead of a mathematical relationship of the measuring parameter values (PARiVALSJBREF), for a reference solder joint of the faulty reference solder joints (SJBREF) of an identical type, to the lower range limiting value (LVDFAi) or the upper range limiting value (UVDFAi) of the respective fault actual-value range (DFAi) specific to a measuring parameter, a mathematical relationship of the derived measuring parameter values (PARiVALAVESJBREF), comprising one of a difference and a ratio, to the lower range limiting value (LVDFAI) or to the upper range limiting value (UVDFAi) of the respective fault actual-value range (DFAi) specific to a measuring parameter is determined; and

during testing of the solder joint (SJ), instead of the measuring parameter value (PAR1VALSJ), a further measuring parameter value (PARi′

VALSJ) of at least one further first measuring parameter (PARi′

) is ascertained, for which the derived measuring parameter value (PARiVALAVESJBREF) of the third number (o) of the faulty reference solder joints is one of closest to and furthest from the lower range limiting value (LVDFAi) of the fault actual-value range (DFAi), as compared with other fault actual-value ranges (DFA3, . . . DFAm) specific to a measuring parameter, or for which the derived measuring parameter value (PARiVALAVESJBREF) of the third number (o) of faulty reference solder joints one of furthest from and closest to the upper range limiting value (UVDFAi) of the fault actual-value range (DFAi), as compared with other fault actual-value ranges (DFA3, . . . , DFAm) specific to a measuring parameter.

24. The circuit arrangement according to claim 20, wherein the control program is configured such that one the lower range limiting value (LVDFAi) and the upper range limiting value of the fault actual-value range (DFAi) specific to a measuring parameter is determined as a function of a measuring parameter value in which a faulty solder joint has an inadequate contact area between solder material and contact element (PIN).

25. The circuit arrangement according to claim 20, wherein the control program is configured such that one of the upper range limiting value (UVDFAi) and the lower range limiting value of the fault actual-value range (DFAi) for a measuring parameter is determined as a function of a distribution function of measuring parameter values (PARi) of the fault-free reference solder joints (SJREF).

26. The circuit arrangement according to claim 20, wherein the control program is configured such that:

the distribution function of measuring parameter values (PARi) of the fault-free reference solder joints is a normal distribution; and

one of the upper range limiting value (UVDFAi) and the lower range limiting value of the fault actual-value range (DFAi) specific to a measuring parameter is determined as a function of a standard deviation.

27. The circuit arrangement according to claim 20, wherein the control program is configured such that one of the upper range limiting value (UVDFAi) and the lower range limiting value of the fault actual-value range (DFAi) for a measuring parameter is fixed to a value which is slightly smaller or greater than the measuring parameter value of a still fault-free reference solder joint (SFGREF).

28. The circuit arrangement according to claim 20, wherein the control program is configured such that a solder joint (SJ) is judged to be fault-free during testing if the measuring parameter value is one of at least as large and at most as small as a predefinable, first threshold value (Ti1) for a measuring parameter.

29. The circuit arrangement according to claim 28, wherein the control program is configured such that the first threshold value (Ti1) for a measuring parameter is of the same size as the upper range limiting value (UVDFAi) of the fault actual-value range (DFAi) for the measuring parameter.

30. The circuit arrangement according to claim 29, wherein the control program is configured such that a solder joint (SJ) is judged to be fault-free during the testing if a measuring parameter value is at least as large as a predefinable, second threshold value (Ti2) specific to a measuring parameter, which threshold value differs, by a threshold value deviation (ia) specific to the measuring parameter, from the first threshold value (Ti1) specific to the measuring parameter.

31. The circuit arrangement according to claim 30, wherein the control program is configured such that one of the magnitude of a permissible threshold value deviation (a), specific to a measuring parameter, of a first measuring parameter, and the magnitudes of further permissible threshold value deviations (b, c), specific to a measuring parameter, of further measuring parameters is determined as a function of a predefinable reference value (CTAREF) of a mathematical combination of the threshold value deviations (a, b, c), comprising one of a product, an average and a sum of the threshold value deviations.

32. The circuit arrangement according to claim 30, wherein the control program is configured such that one of the magnitude of a permissible threshold value deviation (a), specific to a measuring parameter, of a first measuring parameter, and the magnitudes of further permissible threshold value deviations (b, c), specific to a measuring parameter, of further measuring parameters is determined as a function of a predefinable reference value (CTAREF) of a contact area (CTA) formed between the solder material (SM) and contact element (PIN) of a solder joint (SJ) to be tested.

33. The circuit arrangement according to claim 32, wherein the control program is configured such that:

an item of information which designates the probability of the existence of an electrical contact between solder material (SM) and a contact element (PIN) is formed as a function of measuring parameter values of first measuring parameters; and

the magnitude of the contact area (CTA) is determined based on measuring parameter values of second measuring parameters.

34. The circuit arrangement according to claim 33, wherein the control program is configured such that the magnitude of the contact area (CTA) is determined based on an item of information which designates at least one of a longitudinal extent (ml) of the solder joint (SJ, SJREF), a width extent (b) of the solder joint (SJ), a valley width (v) of a cross section of the solder joint (SJ), a first height difference (hp) between a vertex point (heel) and a valley point (pad) of the solder joint, a second height difference (phd) between the valley point (pad) of the solder joint (SJ) and the substrate (BOARD), a fall (neg) in an edge region of the solder joint (SJ), a rise (sl) in an edge region of the solder joint (SJ), and a quantity of material (d) in a predefinable region of the solder joint (SJ).

39. A circuit arrangement of testing a solder joint (SJ) for freedom from faults by means of X-rays, wherein:

the solder joint (SJ) is arranged on a substrate (BOARD),

solder material (SM) of a fault-free solder joint (SJ) is connected electrically to a contact element (PIN) of a component (CMP), and

the solder joint (SJ) is assigned to a predefinable solder-joint type as a function of a shape of the contact element (PIN) in the region of the solder joint (SJ),

the circuit arrangement includes a processor for performing a control program that is configured such that the solder joint (SJ) is tested to determine a magnitude of a contact area (CTA) formed between the solder material (SM) and contact element (PIN);

the magnitude of the contact area (CTA) formed between the solder material (SM) and contact element (PIN) is compared with a predefinable contact-area reference value (CTAREF); and

the solder joint (SJ) is judged to be a fault-free solder joint (SJG) or to be a faulty solder joint (SJB) as a function of a result of the comparison.

40. The circuit arrangement according to claim 39, wherein the control program is configured such that:

an item of information which designates a probability of the existence of an electrical contact between the solder material (SM) and contact element (PIN) is generated as a function of measuring parameter values of first measuring parameters (PM1); and

the magnitude of the contact area (CTA) is determined as a function of measuring parameter values of second measuring parameters (PM2).

41. The circuit arrangement according to claim 40, wherein the control program is configured such that:

the first measuring parameter is a measuring parameter which designates at least one of a meniscus of a solder joint and solder material (SM) arranged laterally on the contact element (PIN); and

the second measuring parameter designates at least one of a longitudinal extent (ml) of the solder joint (SJ, SJREF), a width extent (b) of the solder joint (SJ), a valley width (v) of a cross section of the solder joint (SJ), a first height difference (hp) between a vertex point (heel) and a valley point (pad) of the solder joint, a second height difference (phd) between the valley point (pad) of the solder joint (SJ) and the substrate (BOARD), a fall (neg) in an edge region of the solder joint (SJ), a rise (sl) in an edge region of the solder joint (SJ), and a quantity of material (d) in a predefinable region of the solder joint (SJ).