EP3433045A1

EP3433045A1 - Diagnostic solder frame and method for detecting contaminants in a solder bath of a soldering installation

Info

Publication number: EP3433045A1
Application number: EP17710885.9A
Authority: EP
Inventors: Dietmar Birgel; Thomas Striegel; Michael Feucht; Siegfried Schmierer; Dieter SENN
Original assignee: Endress and Hauser SE and Co KG
Current assignee: Endress and Hauser SE and Co KG
Priority date: 2016-03-21
Filing date: 2017-03-14
Publication date: 2019-01-30
Also published as: WO2017162481A1; DE102016105182A1; CN108778593B; CN108778593A

Abstract

The present invention relates to a diagnostic solder frame (1) for detecting contaminants in a solder bath (3) of a soldering installation, said diagnostic solder frame (1) being configured such that, by means of a transport system (6) of the soldering installation, said diagnostic solder frame (1) can be moved through the soldering installation, and said diagnostic solder frame (1) comprising at least one container (8) with at least a first (9) and a second (11) opening, a first temperature sensor (10), and an evaluation unit (14). The container (8) is arranged such that, during the movement through the soldering installation, a predefinable quantity of solder (3b) passes out of the solder bath (3) through the first opening (9) into the container (8). The temperature sensor (10) projects through the second opening (11) of the container (8) into the container (8) and is arranged so as to be in thermal contact with the predefinable quantity of solder (3b), and serves at least to temporally sense the temperature in the form of a temperature curve (T, (t)). The evaluation unit (14) then draws a conclusion about the contaminants in the solder bath (3, 3b) at least from the temperature curve (T, (t)). Furthermore, the present invention relates to a soldering installation having a diagnostic solder frame (1) according to the invention, to a method for detecting contaminants in a solder bath (3) of a soldering installation, and to a method for operating a soldering installation.

Description

Diagnostic soldering frame and method for detecting contamination in one

Solder bath of a soldering machine

The invention relates to a diagnostic soldering frame for detecting impurities in a solder bath of a soldering machine, which can accumulate in the solder during operation of the soldering machine. Furthermore, the present invention relates to a soldering machine with a diagnostic soldering frame according to the invention, a method for detecting the

Impurities, as well as a method for operating the soldering machine. Soldering is a thermal process for the cohesive joining of two components, usually to produce a surface alloy. The

Lötverbdingung is usually made by means of a connecting material or solder, usually in the form of an easily meltable metal alloy, which is melted. Furthermore, the use of so-called fluxes is common, which serve to reduce the respective surface during the soldering process, and thus lead to an improvement of the flow and wetting properties of the solder and a reduction in the surface tension of the liquid solder on the respective surface. Soldering methods, which are widely used in electronics and electrical engineering in particular and are known in principle from a large number of publications, include, for example, reflow soldering, wave soldering or wave soldering, or else selective soldering, which in principle represents a variant of wave soldering. While so-called solder pastes are used in reflow soldering, a solder bath is used in wave soldering or wave soldering.

The present invention relates to soldering and soldering processes in which a solder bath is used. In wave soldering, for example, electronic assemblies such as e.g. Printed circuit boards, equipped with electronic components and driven over a solder wave. The solder wave is produced by pumping a perforated plate through a gap or through one or more holes in a solder bath ready liquid solder. By contrast, in selective soldering only defined portions of the assembly come into contact with the solder, for example, by pumping the solder wave through small nozzles whose dimensions are adapted to the dimensions of the surfaces to be soldered.

When using solder baths there is always a risk that

Enrich impurities in an initially pure solder. this happens for example, by absorbing smaller amounts of materials contained in the assembly during the soldering process from the liquid solder. Possible sources of contamination include eg component metallizations as well as preloaded ones

Printed circuit boards. The impurities cause even with small amounts of one

Change in the physical and chemical properties of the solder and usually lead to a deterioration of the achievable with the solder quality of the

Solder joints.

In addition, it is also harmful to health or the environment

Impurities or substances can act. Although restricted the RoHS directive

201 1/65 / EU (Restriction of Certain Hazardous Substances) of the European Union on the use of certain dangerous substances, such as Heavy metals such as lead, mercury, cadmium, or hexavalent chromium, various flame retardants and

Plasticizers, in the electrical industry and are each limits for the concentrations of each potentially hazardous substances, which must be observed in principle.

However, in particular with regard to solder baths, increasing contamination of potentially hazardous substances can not be entirely ruled out over time since such substances are contained in the assemblies to be soldered in specific amounts and, for example, absorbed by the liquid solder with increasing time in continuous operation of the soldering machine and thus can be enriched in the solder bath.

For example, it can lead to an accumulation of lead even with the use of lead-free solders with increasing time in continuous operation of the soldering machine with the same Lotbad. Possible causes in this case are lead-containing component metallizations. Corresponding assemblies are generally standardized and are short-term by different partially changing manufacturers, so that the presence of lead metallization can not always be ruled out with certainty. Theoretically, even with tin / lead pre-soldered printed circuit boards may be a possible cause for the accumulation of lead in an originally lead-free solder. However, since printed circuit boards are usually custom-made for specific applications, they can be specifically excluded as the cause of lead accumulation.

In order to avoid the accumulation of impurities in a solder bath, in particular with respect to substances harmful to health and / or the environment, and to ensure the most constant possible quality of the solder joints produced, solder baths in soldering systems are usually replaced at regular intervals. Each exchange, however, involves considerable time and expense. In addition, the rate at which a given substance accumulates in a solder bath can vary widely. It depends in particular on the components used in each case. Accordingly, the solder bath must either be changed very frequently, or be accepted that the quality of the solder joint with the increasing

Accumulation of impurities in the solder bath decreases. The latter can sometimes lead to a surprisingly rapid enrichment of

Impurities significantly reduced the quality of the solder joints in the meantime.

In order to be able to determine the point in time at which the impurities in a solder bath exceed a predefinable limit value and an exchange of the solder bath becomes necessary, various chemical analysis methods are available for determining the chemical composition of the solder. However, these procedures typically require sampling and submission to a laboratory. Accordingly, there may be several days between the sampling and the presence of a result, which is particularly critical if for a given substance the respective predetermined limit for its concentration in the solder bath has already been exceeded or almost exceeded.

In order to counteract this problem, a soldering system, a method for detecting impurities in a solder bath and a method for operating a soldering system have become known from EP2221 136A1, with which impurities can be detected in a simple manner promptly and on site. This is done by means of a

Temperature sensor, the time course of the temperature of the solder during a Abkühloder or heating, which contains a phase transition of the solder from solid to liquid or vice versa, measured and compared with a reference curve corresponding to the corresponding time course of the temperature for an impurity-free solder. If necessary, existing deviations then provide information about the extent of the impurities. To carry out this analysis, however, either a complex apparatus must be provided by means of which the temperature of the solder bath itself can be detected or, as in the chemical analysis method, a predetermined amount of solder is first removed from the solder bath and thus from a continuous process. In both cases, the actual soldering process usually has to be interrupted for a short time. Furthermore, a cooling or

Melting process of the predetermined amount of solder or the solder bath are brought about to detect the time course of the temperature can. Thus, in EP2221 136A1 several operations included, and thus is as well as the common chemical analysis methods relatively expensive.

The present invention is therefore based on the object to provide an apparatus and a method by means of which the presence of impurities in a solder bath can be determined in a particularly simple manner. This object is achieved by a diagnostic soldering frame, by a method for detecting impurities in a solder bath of a soldering machine, and by a method for operating a soldering machine. With regard to the diagnostic soldering frame, the object according to the invention is achieved by a diagnostic soldering frame for the detection of impurities in a solder bath of a soldering machine,

which diagnosis soldering frame is designed such that it by means of a

Transport system of the soldering machine can be driven by the soldering machine, and which diagnostic soldering frame at least

a container having at least a first and a second opening,

a first temperature sensor, and

- comprises an evaluation unit,

wherein the container is arranged such that during driving through the soldering system a predeterminable amount of solder from the solder bath penetrates through the first opening into the container,

wherein the temperature sensor projects through the second opening of the container into the container and is arranged such that it is in thermal contact with the predeterminable amount of solder,

wherein the temperature sensor at least for temporal detection of the temperature in

Form of a temperature curve is used, and

wherein the evaluation unit makes a statement about the impurities of the solder bath at least from the temperature curve. Advantageously, the presence of contaminants during the continuous operation of a soldering machine can be determined by means of the diagnostic soldering frame according to the invention. A diagnostic soldering frame adapted to a specific soldering system is provided, by means of which, during driving through the soldering machine, a

Temperature curve can be recorded and then compared with a reference curve, which corresponds to the impurities free solder, or even the pure solder.

In this case, the diagnostic soldering frame can have, for example, a memory unit, the memory unit serving to store the time profile of the temperature, which is connected to at least the first temperature sensor and to the evaluation unit or can be connected. This storage unit is preferably mounted on or on the diagnostic soldering frame. In principle, two possibilities are conceivable for the arrangement of the evaluation unit. On the one hand, the evaluation unit may be arranged separately from the diagnostic soldering frame, such that the evaluation unit is not moved through the soldering system together with the diagnostic soldering frame. In this case, the measured temperature curve

for example, temporarily stored in the aforementioned memory unit, which is connected directly to the evaluation unit after passing through. It goes without saying, however, that the evaluation unit can also be arranged on or on the diagnostic soldering frame. In this variant, an attached to or on the diagnostic Lötrahmen power supply, for example by means of a battery is also conceivable.

The statement about impurities is in particular a statement that the amount of impurities is a predefinable limit

exceeds and thus the solder bath should be replaced. In the case of an evaluation unit arranged on or on the soldering frame, this can be arranged, for example, in the form of at least one likewise on or on the diagnostic soldering frame

Display element, such as an audible or visual display element, preferably an LED, are displayed. In the event that the evaluation unit is arranged separately from the diagnostic soldering frame, the evaluation unit and optionally a suitable display element can in turn also be integrated into an existing electronic unit of the soldering system or be arranged together with such an electronic unit.

In a preferred embodiment, the evaluation unit of the invention

Diagnostic soldering frame designed to

determine at least one local extreme point from the temperature curve, which extreme point substantially corresponds to a start time at which the predeterminable quantity of solder penetrates into the container,

starting from the start time to determine a diagnostic time interval in which a cooling or heating of the solder takes place in a temperature range by a phase transition of the solder occurs, wherein at least a quantitatively largest part of the solder in the container solidifies or melts, and

from a comparison of the temperature curve at least during a part of the diagnostic time interval and / or a characteristic derived therefrom with a reference curve recorded under the same conditions or

Reference characteristic, which corresponds to the time course of the temperature of a Referenzlots during heating or cooling process in the temperature range, to determine a possibly existing deviation, and to recognize the solder as contaminated when the deviation exceeds a predetermined limit. The reference solder is preferably the same solder as the solder of the solder bath; However, the reference solder is preferably free of impurities, so a pure solder. However, it can also be a solder, which is deliberately mixed with a known amount of one or more specific impurities.

According to one embodiment of the diagnostic soldering frame according to the invention

the parameter is the temperature at which the temperature curve has a plateau-shaped section,

the reference parameter is the melting temperature of the reference solder, and

the deviation is a difference between the parameter and the

Reference parameter.

A further embodiment of the diagnostic soldering frame according to the invention includes a lid, which lid is designed to releasably close the second opening of the container, and wherein the first temperature sensor is guided through the lid.

The container is preferably embedded in a bore of the diagnostic Lötrahmens and releasably secured there, such that the container is arranged when passing through the soldering on the solder bath side facing the diagnostic soldering frame. In the case that a lid is used, this lid closes the second opening of the

Container, which faces the solder bath facing away from the diagnostic soldering frame.

In one embodiment, the container is designed such that the surface of the container is as large as possible in relation to its volume, wherein the container is preferably designed cup-shaped, conical or hemispherical. A surface area of the container which is large in relation to the volume and in particular maximizes the volume of the container in the framework of the geometrical boundary conditions makes possible a homogeneous and uniform melting or solidification process of the predeterminable quantity of solder in the container during the respective heating or cooling process.

It is also advantageous if the container is a crucible, which is preferably made of a material to which the respective solder does not adhere, in particular stainless steel or Teflon. After passing through the soldering and meeting the statement about the impurities in the solder bath thus the predetermined amount of solder in the solidified state can be easily removed from the container. In a preferred embodiment of the diagnostic soldering frame, the first opening, through which the predeterminable amount of solder penetrates, is arranged in the region of a side wall of the container and / or slit-shaped, oval or round. The predetermined amount of solder then enters the container when the diagnostic soldering frame reaches the position within the soldering machine, at which position the diagnostic soldering frame or container substantially comes into contact with the solder wave for the first time. This time corresponds to the start time for the evaluation unit.

The predeterminable amount of solder is determined, on the one hand, from the dimensions of the solder wave, that is, depending on the type of soldering machine, from the dimensions of the gap of the openings, or the respective nozzle. Furthermore, the transport speed of the diagnostic Lötrahmens and the size of the second opening and the container play a crucial role. Based on these dimensions, the specifiable amount of solder for a particular soldering machine can be set substantially to a constant value.

It is advantageous if the diagnostic soldering frame comprises a second temperature sensor, which is attached outside the container to the diagnostic soldering frame. Preferably, the second temperature sensor is arranged such that it can measure the temperature on the side of the diagnostic soldering frame facing the solder bath,

in particular directly in front of the container with respect to the direction of travel of the diagnostic soldering frame. In this case, the starting time for the evaluation unit either in addition to or instead of the first temperature sensor by means of the second

Temperature sensor can be determined. Since the second temperature sensor, in contrast to the first temperature sensor, is arranged outside the container, it shows a temporally faster, in particular instantaneous, reaction to temperature changes, in particular to a temperature change as a result of the contact with the solder wave, the first one

By contrast, the temperature sensor only comes into contact with the solder wave indirectly via the container and the predeterminable quantity of solder penetrating into the container and thus reacts more slowly.

The object of the invention is also achieved by a soldering machine with

- A solder bath, which contains a liquid solder in the soldering, the

Contain impurities that are in the soldering in the first

enriched pure lot,

- A transport system by means of which a soldering frame can be passed through the soldering, and

a diagnostic soldering frame according to at least one of the preceding claims. In addition, the object according to the invention is achieved by a method for detecting impurities in a solder bath of a soldering machine,

wherein a diagnostic soldering frame is driven through the soldering machine,

wherein the time course of the temperature in a container of the diagnostic Lötrahmens, in which container a predetermined amount of solder from the Lotbad penetrates, is detected in the form of a temperature curve, and

at least from the temperature curve, a statement about the

Impurities of the solder bath is taken. Advantageously, a temperature curve during driving of the diagnostic soldering frame is determined and evaluated by the soldering system. Consequently, a diagnosis, ie a statement about the impurities of the solder bath, can be made automated during the continuous operation of the soldering system.

For this inventive method, it is advantageous if

at least one local extreme point is determined from the temperature curve, which extreme point substantially corresponds to the start time at which the predeterminable quantity of solder penetrates into the container,

starting from the start time, a diagnosis time interval is determined in which a cooling or heating process of the solder takes place in a temperature range by a phase transition of the solder occurs, wherein at least a quantitatively largest part of the solder in the container solidifies or melts, and

Reference characteristic, which corresponds to the time course of the temperature of a Referenzlots during the heating or cooling process in the temperature range, determines a possibly existing deviation, and the solder is detected as contaminated when the deviation exceeds a predetermined limit.

At a certain time during the driving of the diagnostic soldering frame by the soldering system, at least the first temperature sensor is first exposed to the solder wave. This event essentially defines the start time for determining the diagnostic time interval. The measured temperature curve has at this start time a peak, or a local maximum, which is followed by a local minimum. At least one of these two peaks can be advantageously used to trigger the diagnostic time interval by specifying a suitable offset period. The choice of the duration of this offset period depends on the one hand on the respective Lot. Furthermore The transport speed of the diagnostic soldering frame through the soldering system plays a role.

A preferred embodiment of the method for detecting contaminants further includes

that the reference characteristic is the melting temperature of the reference solder, and that the deviation is a difference between the characteristic and the

Reference characteristic is.

Finally, the object according to the invention is achieved by a method for operating a soldering machine,

wherein the soldering system is filled with a reference slot during commissioning, - wherein the diagnostic soldering frame is driven through the soldering machine,

wherein the time course of the temperature in a container of the diagnostic Lötrahmens, in which container a predetermined amount of solder from the Lotbad penetrates, is detected in the form of a reference curve, and

wherein the reference curve and / or derived from the reference curve

Reference characteristic is stored in a memory unit accessible to the evaluation unit, and / or is entered in a process control chart.

The reference solder is preferably the same solder as the solder of the solder bath; However, the reference solder is preferably free of impurities, so a pure solder. However, it can also be a solder, which is deliberately mixed with a known amount of one or more specific impurities. The memory unit in which the reference curve and / or reference parameter is stored is again

For example, the aforementioned storage unit or a separate storage unit, for example, a memory unit associated with an electronic unit of the soldering machine.

For the method according to the invention for operating a soldering system, it is advantageous if a diagnostic measurement is carried out at predeterminable time intervals, the diagnostic soldering frame is moved through the soldering system,

the temporal course of the temperature in a container of the diagnostic soldering frame, in which container a prescribable amount of solder from the solder bath penetrates, in

Form of a temperature curve is detected, and

the temperature curve and / or a characteristic derived therefrom with a reference curve, a reference characteristic and / or with an earlier Time determined temperature curve or the respectively associated characteristic is compared, and

in the case that the deviation between the reference curve, earlier

Temperature curve, reference characteristic, and / or previous characteristic and the current temperature curve and / or characteristic exceeds a predetermined limit, it is detected that the solder is contaminated.

The various embodiments of the method for detecting contaminants can be mutatis mutandis aud method of the invention for operating a soldering apply.

For example, the diagnostic measurement can be repeated every time the soldering system is started up, every working day, or at other periodic intervals. These time intervals can be adapted depending on the application. The operating personnel of the soldering system merely has to ensure that the soldering frame according to the invention is moved through the soldering system according to at least one of the embodiments described and that a corresponding evaluation is carried out. Otherwise, depending on the configuration, no further process steps by the operator are required to determine the presence of impurities.

It is advantageous if each temperature curve and / or characteristic together with the time at which it was detected is stored in the memory unit and / or entered into the process control chart. The diagnostic data, in particular deviations of the respectively measured temperature curves from the reference curve can then be represented as a function of time, for example. Thus, it can be traced at what rate impurities accumulate in the solder bath and predict when an exchange of the solder bath should be done at the latest.

Thus, the present invention allows the detection of impurities contained in a solder bath during continuous operation. Thus, in any

Time intervals are provided on the extent of contamination, wherein the soldering operation is delayed only by driving a diagnostic soldering frame between the successive soldering frames of the soldering machine. This has both a significant time and cost savings and a significant increase in quality of achievable solder joints result. In addition, impurities are detected even if they do not result in a reduction in the quality of the soldering system, which is particularly advantageous in the case of health and / or environmentally harmful substances. The invention will be explained in more detail below with reference to FIGS. 1 to 3. It shows:

1 shows a schematic sketch of a diagnostic soldering frame according to the invention in a soldering system;

FIG. 2 shows a measured temperature curve and a reference curve; FIG. and

Fig. 3 is a block diagram illustrating an embodiment of the method according to the invention for the introduction of a soldering system.

FIG. 1 schematically shows a diagnostic soldering frame according to the invention during the passage through a soldering system with a solder bath. For simplicity, only relevant to the present invention components of the soldering machine are shown. The soldering system comprises a solder bath 2, which comprises liquid solder 3 during the soldering operation. The liquid solder 3 is pumped out by means of a solder guide 5 projecting at least partially into the liquid solder 3, which is a nozzle in the present case, for producing a solder wave 5 above the liquid level of the liquid solder 3 in the solder bath 2. It goes without saying that the present invention is also suitable for other soldering systems with a solder bath 2, in particular for soldering guides 5 in the form of a gap or a hole of a perforated plate.

For soldering, a soldering frame (not shown separately) is equipped with the respective components and by means of a transport system 6 (shown by the dashed line indicating the transport direction) of the soldering machine, such as a conveyor belt, by the soldering machine, and in particular via the solder wave. 5 hazards.

In order to detect contaminants accumulating in the solder bath 2 over time, a diagnostic soldering frame 1 is used according to the invention. The diagnostic soldering frame 1 is adapted to a specific soldering system that he can be driven by the soldering system by means of the transport system 6 of the soldering system. The diagnostic soldering frame comprises a container 8 in which, during driving through the soldering system, a prescribable quantity of solder 3b penetrates when the container 8 is moved over the solder wave 5. In the embodiment shown here, the container 8 is embedded in a bore of the diagnostic soldering frame 1 and fixed there. The container 8 protrudes beyond the edge of the diagnostic soldering frame 1 on the side of the diagnostic soldering frame facing the soldering bath. Of course, other geometries can be selected for the arrangement of the container 8 on or on the diagnostic soldering frame 1. The container 8 has a first 9 and a second 1 1 opening. By the first Opening 9 penetrates a predeterminable amount of solder 3b during the driving of the diagnostic soldering frame 1 through the soldering system as soon as the diagnostic soldering frame substantially comes into contact with the solder wave 5 for the first time. For the design of the first opening 9, it must be ensured that the predeterminable amount of solder 3b can actually penetrate into the container 8 during the passage through the soldering system. For this purpose a variety of arrangements and geometries are conceivable. In that shown in Fig. 1

Embodiment, the first opening 9 is exemplified in the form of a slot which extends with its longitudinal axis parallel to the longitudinal axis of the diagnostic Lötrahmens 1 and has a length which corresponds substantially to half of the circumference of the container.

The second opening 1 1 a of the embodiment of FIG. 1 cup-shaped container 8 substantially terminates with the Lotbad 3 remote from the surface of the Lötrahmens-body 7 and is closed by the lid 1 1. Through the lid, a first temperature sensor 10 is guided, which is arranged such that it is in thermal contact with the predetermined amount of solder 8 after their penetration into the container 8. It should be noted, however, that the cover 1 1 represents an optional component for the diagnostic soldering frame 1 according to the invention. A further optional component is provided by a second temperature sensor 12, which is arranged in the region of the solder bath 3 facing side of the solder frame body 7 and which also comes when passing through the soldering machine with the solder wave in contact.

For the embodiment shown in FIG. 1, both temperature sensors 10, 12 are connected by way of example to a memory unit 13, which is arranged on the soldering frame body 7 and connected to an external evaluation unit 14 with an optical display element 15. Some possible other variants have already been mentioned before.

The use of a diagnostic soldering frame 1 according to the invention allows an automated evaluation of the recorded temperature curves and the automated generation of information about the contaminants. To explain this

2, a measured temperature curve T, (t) and a reference curve T _ref (t) for the same solder, once with and once without impurities, during a cooling process after penetration of the predetermined amount of solder 3b in the container 8.

Upon initial contact with the solder wave, the temperature curve has a maximum value Tmax (tmax) followed by a local minimum. Both extremes are suitable for defining the start time t ₀ ; for the embodiment of FIG. 2, however, defines that local minimum the start time to. Starting from the starting time t ₀ , a suitable offset period At _{os is} indicated, which is selected as a function of the respective solder and the transport speed of the transport system 6 of the soldering machine. After the offset period At _os , the diagnosis time interval At _D begins, which is used for the actual evaluation of the temperature curves Tj (t). For the embodiment according to FIG. 2, the duration of the diagnostic time interval At _D is selected so that it essentially corresponds to the plateau-shaped section of the respective temperature curve Tj (t). This section corresponds to a phase transition of the solder 3 during a cooling process in a temperature range in which a phase transition takes place, in which a

quantitatively largest part of the solder 3 in the container 8 solidifies.

The temperature curves T, (t) and T _ref (t) shown in FIG. 2 correspond to the case where a certain impurity essentially leads to an increase in the melting temperature of the solder as a function of the concentration of the impurities from T ₁ to T _ref . The mean value of the measured temperatures in the plateau-shaped section can then be used in this case, for example as parameter T _m or as reference characteristic T _ref . If the deviation between the parameter and reference parameter ΔΤ = Τ _Γ Τ _{Γβί exceeds} a predefinable limit value, the solder is recognized as contaminated. The same procedure applies in the case of a through the

Impurities caused reduction of the melting temperature of the solder 3.

In principle, it is exploited that the time characteristic of the temperature T, (t) of a solder 3 during a phase-transition-containing heating or cooling process has a sensitive dependence on its chemical composition. Even slight concentrations of an impurity of 0.1 atomic% usually already lead to a significant change in the course of a temperature curve Τ, (ί). This applies both to impurities with foreign substances, which are not part of the

Lots of metal alloy are, as well as for variations in the composition of the solder.

The temperature curves Tj (t) and T _ref (t) shown in FIG. 2 represent only one of many cases of how the accumulation of impurities on the course of a

Temperature curve Tj (t) compared to a corresponding reference curve T _ref (t) can affect. The change in the course of a temperature curve T, (t) with respect to a reference line T _ref (t) corresponding to an impurity-free solder depends sensitively on both the type and the amount of impurities, so that for the respectively expected impurities If necessary, a suitable type of comparison of the respective temperature curves T, (t) and T _ref (t) must always be selected for certain lots 3. To explain the effect of impurities on the course of measured temperature Tj (t) should in particular also be referred to the explanations in EP2221 136A1 with reference to Figure 3, to which reference is hereby fully made.

It should also be noted that accessible in one of the evaluation

Memory unit and several different evaluation algorithms for determining deviations between the temperature curves Tj (t) and T _ref (t) can be stored, which can be either automated or selected by an operator.

The operation of a soldering system for which a diagnostic soldering frame 1 according to the invention can be used is illustrated by way of example with reference to the block diagram in FIG. 3. Preferably, when starting up the soldering machine and / or directly after filling the soldering machine with a solder bath free of impurities, first a

Reference measurement performed. The diagnostic soldering frame 1 is moved through the soldering system and detected for the reference measurement of the time course of the temperature in the form of a reference curve T _ref (t) in a temperature range containing a phase transition by means of the first temperature sensor. Subsequently, for example, a reference parameter T _ref can be determined from the reference curve T _ref (t). Both the

Reference curve T _ref (t) and the reference characteristic T _ref can be stored in a memory unit. In addition, a process control card can be created and at least the reference characteristic T _{ref can be} entered in the process control chart.

Subsequently, a diagnostic measurement can be performed at predetermined time intervals. Here again, the diagnostic soldering frame 1 is driven through the soldering system and a temperature curve T, (t) detected and possibly derived therefrom a parameter T _m .

Subsequently, the deviation AT = T _rer T _m between the reference characteristic T _ref and the characteristic T, is determined. Is the deviation ΔΤ greater than a predeterminable limit value for the deviation AT | _im , either a repetition of the

Diagnostic measurement performed, or indicated that the Lotbad must be replaced. Possibly. The continuous operation of the soldering machine is also automatically interrupted. Exceeds the deviation ΔΤ the predetermined limit value for the deviation AT | _in contrast, the process is released, for example by a suitable signaling by means of a display element 15. The measured at a given time i temperature curve Tj (t) and possibly the associated characteristic T, can also be stored in the memory unit and / or in the process control chart is entered. If corresponding temperature curves Tj (t) are carried out and documented at short and regular time intervals, the rate at which contaminants accumulate can also be determined. This allows the operators of a Soldering an increased planning possibility for any necessary exchanges of the solder bath.

In order to determine the rate at which impurities accumulate, it is also possible to create a plurality of reference curves for which the solder is purposefully contaminated with different but known amounts of the respective substance. Then, a comparison of the measured rate can be performed with a reference rate determined from the various reference curves. This is particularly useful if the

Impurities would lead to a strong reduction in quality of the respective solder joints even at low levels of impurities.

Performing repeat measurements ensures a redundant determination of the presence of impurities, which is particularly the case in which the measured values of the respective temperature curve T, (t) are subject to errors.

However, it should be noted that the use of a diagnostic Lötrahmens invention, in contrast to the known methods ensures a particularly high degree of reproducibility, since always the same amount of solder from the solder bath is removed in the same manner. Thus errors of the respective measured values, which from a special kind of the removal or from a special kind of the

Temperature measurement result, can be avoided. This constitutes a further advantage of the present invention.

Reference numerals and symbols

1 diagnostic soldering frame

2 containers of the soldering bath of the soldering machine

3 solder bath

3b specifiable amount of solder in the container

4 solder guide

5 solder wave

6 transport system

7 soldering frame body

8 containers

9 First opening in the container

10 First temperature sensor

1 1 Second opening in the container

1 1 b cover

12 second temperature sensor

13 storage unit

14 evaluation unit

15 indicator

T temperature

t time

Tj (t) temperature curve at time i

Tj characteristic

Tref (t) reference curve

Tref reference parameter

Tmax maximum temperature

to start time

At _os offset period

At _D diagnostic time interval

ΔΤ Deviation between reference characteristic and characteristic

ΔΤ predefinable limit value for the deviation

Claims

claims

1. diagnostic soldering frame (1) for detecting impurities in a solder bath (3) of a soldering machine,

which diagnosis soldering frame (1) is designed such that it by means of a

Transport system (6) of the soldering machine can be driven by the soldering machine, and which diagnostic soldering frame (1) at least

a container (8) having at least a first (9) and a second (11) opening,

- A first temperature sensor (10), and

an evaluation unit (14) comprises

wherein the container (8) is arranged such that during driving through the soldering system a predeterminable quantity of solder (3b) from the solder bath (3) penetrates through the first opening (9) into the container (8),

wherein the temperature sensor (10) through the second opening (1 1) of the container (8) protrudes into the container (8) and is arranged such that it with the predeterminable

Quantity of solder (3b) is in thermal contact,

wherein the temperature sensor (10) at least for temporal detection of the temperature in the form of a temperature curve (T, (t)) is used, and

wherein the evaluation unit (14) at least from the temperature curve (T, (t)) makes a statement about the impurities of the solder bath (3,3b).

2. diagnostic soldering frame (1) according to claim 1,

wherein the evaluation unit (14) is designed to

determine from the temperature curve T, (t) at least one local extreme point, which extreme point substantially corresponds to a starting time (t ₀ ), at which the predeterminable amount of solder (3b) penetrates into the container (8), starting from the start Time (t ₀ ) to determine a diagnostic time interval (At _D ), in which a cooling or heating of the solder (3b) in a

Temperature range takes place by a phase transition of the solder (3b) occurs, in which at least a quantitatively largest part of the solder (3b) in the container (8) solidifies or melts, and

from a comparison of the temperature curve (T, (t)) at least during a part of the diagnosis time interval (At _D ) and / or a characteristic quantity derived therefrom (T,) with a reference curve (T _ref (t)) recorded under the same conditions or Reference characteristic (T _ref ), which is the time course of the temperature of a

Referenzlots during heating or cooling process in the temperature range corresponds to determine a possibly existing deviation (ΔΤ), and to recognize the solder (3,3b) as contaminated when the deviation (ΔΤ) exceeds a predetermined limit (AT | _im ).

3. diagnostic soldering frame (1) according to claim 2,

in which

the parameter (T,) is the temperature at which the temperature curve has a plateau-shaped section,

- The reference characteristic (T _ref ) is the melting temperature of the reference slot, and the deviation (ΔΤ) is a difference between the characteristic (T,) and the

Reference parameter (T _ref ) is.

4. diagnostic soldering frame (1) according to at least one of the preceding claims, with a cover (1 1 b), which cover (1 1 b) is configured to the second opening

(1 1) of the container (8) releasably close, and wherein the first temperature sensor (10) through the lid (1 1 b) is guided.

5. diagnostic soldering frame (1) according to at least one of the preceding claims, wherein the container (8) is designed such that the surface of the container (8) is as large as possible, wherein the container (8) preferably designed pot-shaped, conical or hemispherical is.

6. diagnostic soldering frame (1) according to at least one of the preceding claims, wherein the container (8) is a crucible, which is preferably made of a material to which the respective solder does not adhere, in particular stainless steel or Teflon.

7. diagnostic soldering frame (1) according to at least one of the preceding claims, wherein the first opening (9) through which the predetermined amount of solder (3b) penetrates, in the region of a Seitenbewandung of the container (8) is arranged and / or slit-shaped , oval or round.

8. diagnostic soldering frame (1) according to at least one of the preceding claims, with a second temperature sensor (12) which outside of the container (8) on the

Diagnostic soldering frame (1) is attached.

9. Soldering with

- A solder bath (3), which contains a liquid solder in the soldering, the

Contain contaminants that have accumulated in the soldering operation in the initially pure solder,

- A transport system (6), by means of which a soldering frame can be passed through the soldering, and

- A diagnostic soldering frame (1) according to at least one of the preceding claims.

10. A method for detecting impurities in a solder bath (2) of a soldering system according to at least one of the preceding claims,

wherein a diagnostic soldering frame (1) is driven through the soldering machine,

wherein the temporal course of the temperature in a container (8) of the diagnostic Lötrahmens (1), in which container (8) a predetermined amount of solder (3b) from the Lotbad (3) penetrates, in the form of a temperature curve (T, ( t)), and wherein at least from the temperature curve (Tj (t)) a statement about the

Impurities of the solder bath (3,3b) is taken.

1 1. A method according to claim 10,

wherein at least one local extreme point is determined from the temperature curve (T, (t)), which extreme point substantially corresponds to the start time (t ₀ ) at which the predeterminable quantity of solder (3b) penetrates into the container (8), wherein starting from the start time (t ₀ ), a diagnosis time interval (At _D ) is determined, in which a cooling or heating of the solder (3b) in a

wherein from a comparison of the temperature curve (Tj (t)) at least during a portion of the diagnostic time interval (At _D ) and / or derived therefrom

Characteristic (T,) recorded under the same conditions

Reference curve (T _ref (t)) or reference characteristic (T _ref ), which corresponds to the time course of the temperature of a reference slot during the heating or cooling process in the temperature range, determines a possibly existing deviation, and the solder (3,3b) as contaminated is detected when the deviation

(ΔΤ) exceeds a predefinable limit (AT | _im ).

12. The method according to claim 10 or 1 1,

wherein the characteristic (T,) is the temperature at which the temperature curve has a plateau-shaped section,

wherein the reference characteristic (T _ref ) is the melting temperature of the reference solder, and

wherein the deviation (ΔΤ) is a difference between the characteristic (T,) and the reference characteristic (T _ref ).

13. A method for operating a soldering system according to at least one of the preceding claims,

wherein the soldering system is filled at startup with a reference slot, wherein the diagnostic soldering frame (1) is driven through the soldering machine, wherein the temporal course of the temperature in a container (8) of the diagnostic soldering frame (1), in which container (8) a predetermined amount of solder (3b) from the Lotbad (2) penetrates, in the form of a reference curve (T _ref ( t)) is detected, and wherein the reference curve (T _ref (t)) and / or (from the reference curve T _ref (t)) _ref derived reference parameter (T) in one of the evaluation unit (14) accessible memory unit (13) deposited is, and / or in one

Process control chart is entered.

14. The method according to claim 13,

wherein a diagnostic measurement is performed at predeterminable time intervals, wherein the diagnostic soldering frame (1) is driven through the soldering machine,

wherein the temporal course of the temperature in a container (8) of the diagnostic soldering frame (1), in which container (8) a predetermined amount of solder (3b) from the Lotbad (2) penetrates, in the form of a temperature curve (T, ( t)), and - wherein the temperature curve (T, (t)) and / or a characteristic variable (Tj) derived therefrom with a reference curve (T _ref (t)), a reference characteristic (T _ref ) and / or with a compared to a previously determined temperature curve (T _j (t)) or the respectively associated characteristic (T _j ) is compared, and

wherein, in the event that the deviation (ΔΤ) between the reference curve (T _ref (t)), previous temperature curve (T _j (t)), reference characteristic (T _ref ), and / or earlier

Characteristic (Tj) and the current temperature curve (T, (t)) and / or characteristic (Tj) exceeds a predetermined limit (AT | _im ), it is detected that the solder (3,3b) is contaminated.

15. The method according to claim 13,

wherein each temperature curve (T, (t), T _j (t)) and / or characteristic (T _j , T _j ) together with the time (i, j) at which it was detected, stored in the memory unit (13) and / or is entered in the process control chart.