DE202009012468U1 - Measuring device for faulty components - Google Patents

Abstract

Measuring equipment suitable for laboratory, production, quality control and production, for universal, online-capable, metrological detection of quality errors on integrated in the measuring circuit, mostly hidden, mostly not metrologically detected or contactable vulnerabilities, inaccessible components, joints, cold solder joints o in simple and complex electrical and electronic circuits, with which the complex impedance of a component or a measuring circuit can be measured as a linear dipole and in particular complex impedance parameters, such as damping, quality and loss factor u. a. can be detected, characterized in that an additional device is present, by means of which in a measuring operation of the complex electrical impedance of a two-terminal measuring device temporally offset, simultaneously or temporarily by externally initiated, externally excited energetic stimulation of the measuring circuit or a singular component or a weak point, such cold solder joint, in the complex impedance parameter values in the event of a fault to cause a significant change, which can be measured and evaluated by means of the measuring device.

Description

The Invention relates to a measuring device suitable for laboratory, Manufacturing, quality control and production, for universal, online-capable, metrological recording of quality defects integrated in the measuring circuit, mostly hidden, mostly not metrologically detectable or contactable vulnerabilities, inaccessible Components, joints, cold solder joints o. Ä. in simple and complex electrical and electronic circuits, the complex impedance of the component or of the measuring circuit, as linear two-pole, is measured and in particular complex impedance parameters, such as damping, quality and loss factor u. a. detected become.

All electrical, electronic and electromechanical components, such as also have their assembly to electrical and electronic circuits due to their different production, their installation and their Assembly in production and production also different Total quality features. Therefore, in the statistical Quality control different types of examination and Standards to obtain reliable control values, which give a statement about the lifetime and probability of failure.

Especially often quality defects occur during assembly, assembly, soldering, assembly of connections and connections on.

With the well-known, and above-mentioned, electrical Test methods may be used by function, component or in-curcuit tests almost all component test criteria be recorded. Statistically, very often Failure rate and quality defects are mistakes that in connections, soldering, vias or the like. occur. Representative here is the cold solder joint be mentioned. With known electronic measuring instruments their malfunction can often not be detected. Often only in the case of long-term loading and continuous operation does the fault occur on. It comes to early failures, usually with functional failure, until overheating and burning.

the The person skilled in the art is known by tapping and bending printed circuit boards z. B. trace interruptions or cold solder joints locate or locate.

A exact, physical, metrological recording, with evaluable Limits, is not so production-oriented and in online operation feasible.

An examination of solder joints is from the utility model application DE 298 23 250 U1 known. This document describes an X-ray examination.

In the patent application DE 41 43 546 C2 an optical test by means of laser techniques is proposed.

In the EP 0 124 761 A1 there is provided a method of testing circuits containing samples. This can be determined by wiring with external power sources, whether a current source or a current sinking behavior is present. A concrete, physical parameter measurement is therefore not possible.

One reliable electrical test method, with direct or indirect contact, for measurement and testing of faulty electrical components, eg. B. cold solder joints, is not known.

It The object of the invention is a measuring device and a method for physical, metrological acquisition, analytical evaluation and control of diminished, qualitative product properties, to find and metrologically detect hidden, unknown Weak points, such. B. of cold solder joints within an electrical or electromechanical functional unit to offer.

The Application should be universal, suitable, both for individual components, Connectors, o. Ä., Or on wiring harnesses, Assemblies, modules and complex switching units, an exact measurement and to obtain test result with which an automatic Good / bad selection and evaluation can be made.

The Task is solved in that an additional device is present, by means of the one during a measurement of the complex electrical impedance of a two-pole matrix measuring device in time offset, simultaneously or temporarily by externally initiated, externally excited energetic stimulation of the measuring circuit or a singular component or a weak point, such as cold Solder joint, in the complex impedance parameter values in Failure to evoke a significant change, which can be measured and evaluated by means of the measuring device.

A The object of the invention is the requirement, known, production-tested, the complex impedance measuring, high-precision measuring instruments with Parameter resolution and suitable interfaces.

The measuring device according to the invention includes an additional device, with the particular During and parallel to the measuring process, a locally limited, defined, externally generated energetic stimulation is caused on an individual component of the measuring circuit.

The Function of the additional device should be electrical, non-reactive and should not burden or endanger the meter.

The Measurement method should be online-enabled. The measuring time should be << 1 sec.

The inventor has, inter alia, the following considerations:
It is known and customary to check switching units, modules, single or semi-finished parts prior to assembly in order to identify and sort out missing parts at an early stage, with little loss of value added.

It is known that all physical bodies, conducting, semiconducting or insulating, a complex, electrical Have resistance or impedance with capacitive, inductive and resistive properties. According to these characteristics they react individually with electromagnetic excitation or load differently.

These Legality is z. B. in the electrical Test applied in 2- and 4-pole technique.

The most well-known measuring devices are: LCR measuring bridges, Milli / micro-ohmmeters, vector voltmeters, impedance analyzers, and more. v. a. Here, the measuring circuit to be examined becomes an electrical oscillating circuit considered and measured. With AC technology and at different Measuring frequencies, the test specimen here is different, changing exposed to electromagnetic stress. This is by means of constant alternating current load of the DUT and simultaneously the voltage measured on the test specimen.

through complex measured value processing, it is possible to use all the impedance parameters to determine a candidate. The most important parameter sizes are Quality, damping, dissipation factor, inductance, Capacity, resistance. They provide a physically reliable Measure for quality determination and selection.

Most of time if a measuring circuit to be tested consists of the composition a variety of components, with different, often Inaccessible connection points and connection types. In The practice is therefore only for economic reasons contacted and measured at the input and output terminals. The The measured values and parameters obtained thereby describe the electrical system Overall behavior of the measuring circuit. Information regarding individual component parameters or parameters of individual Weak points, z. B. cold solder joints, low quality Vias on printed circuit boards, trace interruptions, crimping, Plug connections, clamping points, u. Ä. Connection types and Although joining techniques are included in the overall result, they but are of the order of magnitude not or very difficult to read. So gives an overall measurement The connecting poles of the measuring circuit usually no digestion or Indication of weaknesses, short-term or long-term failures can cause.

According to the invention recognized a fundamental disadvantage: All known complex Impedance measuring methods measure with reduced, component-saving Power. The results are highly accurate, the candidate however, it is not energetically charged to its true behavior including the vulnerability to show at rated load. Therefore, measurements of defects, such as cold solder joints, show poor Vias on printed circuit boards, insufficient clamping or connectors, wiring harnesses, circuit boards, modules and complex circuits no evaluable parameter differences to good parts, although there are defects.

This means and requires the following to find a suitable solution:
The error to be detected according to the invention can be detected with the complex measuring instruments described above.

Of the Measuring circuit or a point to be examined of the measuring circuit is additionally energetic during the measuring process stimulated.

The energetically exciting additional device may during the measuring process no disturbing or destructive electrical feedback exercise on the meter.

The energy of the excitation device should be able to be introduced externally into the measuring circuit and locally localized and selectively (to 2 ... 3 mm ² ) be restrictable in order not to stimulate neighboring components.

Thus, the qualitative design of the connection points of the individual components of a measuring circuit determine its overall quality and quality. So z. For example, cold solder joints do not easily distinguish between a dual state, good or bad, and can not be readily detected by measurement. Even with less quality processing, such a solder joint, with respect to their mode of action, just barely work. But it can also early after a short period of operation failures or lead to late losses.

Therefore According to the invention, the user, examiner in production, laboratory and manufacturing for statistical quality control suitable tool can be provided, the it allows a classification of impedance parameters to good parts to create. With this classification, he is able to an individual company and product calibration of his Component, DUT or loop to make about upper and lower limits for electrical test criteria and create measurement parameters, with the goal, even apparent good parts with probable early or late failure behavior to identify and sort out in production or in online operation.

According to the invention were for selecting the principle of action of the energetic auxiliary device all physically possible types of energy (such as: electric: Load with rated current or excessive current load, acoustic: sound, ultrasound, mechanical: tension, pressure, vibration, thermal: heating element, radiation-optical: laser, radiation-physical: X-ray, magnetic, capacitive, inductive or eddy current method) tested, evaluated according to the above criteria and tested.

To the above selection specifications of the invention objective, such as electric Reactive to measuring circuit, online capability, Measuring time << 1 sec and punctual Focusability of the energy remain advantageous as the mechanical Stimulation and thermal stimulation.

The Thermal stimulation has the advantage of providing detectable measurement parameter changes tan d and damping, already at about 100 ° C. At higher Temperatures are much higher and better evaluable Detection values achievable.

Of the Disadvantage here is: The temperature load for testing and adjacent components is not exactly taxable and limited. In particular, with short measurement times, z. B. in online mode from <1 sec, one metrologically, sufficient thermal response of the stimulated Inspection Center is not or not sufficiently done.

The mechanical stimulation, e.g. B. with a vibration transducer has the advantage: the oscillation frequency is controllable. The vibration amplitude is finely adjustable in x and y direction.

So became the principle of action of the energizing accessory The mechanical stimulation is examined and built up in more detail. With the Complex impedance measuring LCR bridges were measured on good parts and on bad parts made, each with and without externally initiated mechanical stimulation on cold solder joints.

at the bad parts were z. B. aware of cold solder joints been produced.

Without mechanical stimulation showed good and bad parts a good one Overall function, good resistance / impedance values, good quality Q, good tan d values, good impedance and capacitance values.

at mechanical stimulation did not show any parameter changes in good parts. Bad Parts However, even with short mechanical stimulation showed clear Measurement parameters change.

Of the occurring physical effect with mechanical stress stimulation on components, eg. B. cold solder joints will be below explained. At cold solder joints are many elemental contact points the soldering partner on the surface roughness profile only loosely, by adhesion, Frictional connection, form fit not yet metallic, rigid, crystalline connected to the solder. There is sometimes no galvanic material connection and only partial alloy closure.

Under mechanical stress alternating load (energetic stimulation approx by vibration), all elemental contact / element contact points become at the cold soldering point individually elastomechanically deformed in the roughness profile, by Tensile and compressive forces. It comes to crystalline, galvanic contact lifts or contact changes. These result in partial and changing current densities, as a result Kontakteinschnürungen. Even if it has not become one absolute contact separation comes, is changing However, the resistive, capacitive and inductive behavior of the joining partners and influences the measuring circuit and can be detected metrologically.

The found measurement results have now been considered in detail and compared. The results also allow a statistical Classification and are described as follows.

Measurement without mechanical stimulation:

at Good parts, all parameter values are constant.

The parameter values of the bad parts hardly differ from those of the good parts, except for the damping values D. In this case, parameter differences of 30% to 70% compared to the good values or more can already be measured. This is z. B. a first classification step, such as for expected short-term failures (at high parameter differences) and about for long-term failures (at low Parameter differences).

These Parameter measurements are all exactly reproducible and repeatable, without the values changing.

Measurement with stimulation:

1st case:

Without mechanical stimulation are all parameter values as good or approximate good measurable.

Become Good parts mechanically stimulated during the measurement, remain their parameters unchanged.

at mechanically stimulated bad parts change almost all Measurement parameters (eg Rs, Ls, Cs, tan d, D, Q) their values. Especially extremely the loss angle tan d (from 1 ° ... at ... 85 °) and the damping D (from about 890 ... on ... 3,0).

To stimulation, these values return to their good values. These are long-term errors.

A First classification for error selection is possible hereby.

2nd case:

Without Stimulation, all parameter values are good or approximate Good. When paced, all parameters change to marginal Values.

To stimulation, these values do not return to their good values back, they stay bad. The original supposed good-part has become a bad part. The included parameter errors are short-term errors. These would have led to early failures. Through this They have failed and can be considered bad to be sorted out, 2nd classification.

Conclusion of the measurement results:

The Complex impedance measurement, with AC source and contacting according to the known four-conductor or Kelvin method enabled a metrological acquisition of all resonant circuit parameters.

Around a sensitive electrical measuring circuit as low as possible To load, most measuring devices work well under the Rated load with extremely low voltages. This is generally enough, because the electrical resonant circuit behavior only is frequency dependent. High measurement amplitudes are not necessary.

has a mostly high-impedance measuring circuit but defects, weak points, z. As cold solder joints, poor vias on printed circuit boards, insufficiently resilient connectors, incorrect Crimping of terminals u. Ä. the error remains mostly hidden and so is not measurable.

There Measuring circuits usually also different environmental loads in the Operation are exposed, it is common by thermal and mechanical stress tests (heat chambers, Shaking, chute), fall and shock tests, u. ä.) Provoke early failures and vulnerabilities to recognize. However, these tests are not feasible for all circuits or can or will be for cost and effort reasons not done.

Around above-mentioned hidden, metrologically difficult or impossible to detect Vulnerabilities, with existing suitable or to be procured To record, classify and evaluate measuring instruments, is an adjustable, component-compatible, energetic Stress stimulation of the entire measuring circuit, its involved Components or just singular at certain critical Points, z. B. critical solder joints to make.

For this provides the test device according to the invention with stimulator a valuable measurement and decision support.

additionally to the electrical measuring device described above is during the measurement process, briefly, for example, by selective, slight dab, energized in milliseconds the flaw energetically. This can happen thermally, by briefly touching the Tip of a heating device or with a mechanically oscillating Stimulator.

As a result the thermal or mechanical stress load changed elastomechanical the crystalline structure of the test site and thus the resistive, capacitive and / or inductive behavior the joining partner, influences the measuring circuit and can metrologically be recorded.

in the mechanical stress, especially the impedance parameter values of tan d and attenuation marginal detection and measurement changes.

In summary, the following advantages according to the invention result:
Cold solder joints or hidden material defects can be measured and evaluated with the described measures.

For critical components and weak points, a classification z. For statistical quality control possible.

Short- and long-term errors can be detected.

The electrical measurement is only possible with instruments that perform a complex impedance measurement and the corresponding Represent impedance parameters.

The Additional device according to the invention for stimulation is a simple, effective and inexpensive solution.

Also on sensitive measuring circles of ceramic, glass, o. Ä. Can be measured.

The Measuring and test times are << 1 sec

The Measurement method with this option is online-enabled.

The Measuring method simultaneously provides a mechanical quality stress test in which, by careful and targeted adjustment of frequency and amplitude of the stimulator weak points either already completely fail or show their failure tendency with significant Kennparameterveränderung.

In 1 is a block diagram of the measuring device according to the invention shown. It shows the overall arrangement of the measuring device. The measuring instrument ( 1 ), implemented as an LCR measuring bridge, milli-ohmmeter, impedance analyzer, or similar, includes an alternating current source and a voltage measuring unit, as well as a computing unit that converts the measured values into the impedance and the other mentioned parameter measured values, displays and z. B. via an RS232 interface ( 1.1 ) offers to the measurement evaluation.

higher value Devices already have adjustable limit settings, with their help on the output side, an analogue or high-low signal for good or bad evaluation is available.

Around the two-terminal matrix (measuring circuit ( 5 )), the instruments have 4 measuring terminals: For the separately energized circuit by means of the constant current source (+ I and -I) and for the separately measuring voltage circuit (+ U and -U). This type of measurement is known as a 4-wire or Kelvin measurement method ( 3 ).

The contact on the measuring circuit ( 5 ) is carried out with two Kelvin terminals, buttons or measuring pliers ( 4 ).

The Contacts of these terminals are electrically isolated from each other. This causes that via the one contact of the constant current is initiated directly on the dipole of the measuring circuit. At the same time tapped isolated with the other contact the measuring voltage.

The measuring circuit ( 5 ) represents the two-pole matrix. This may include a single, singular contacting of a component, connector, feedthrough or cold solder joint. Or it can also involve the two-pole measurement of a complex measuring unit, consisting of an interconnection of R, L and C elements. In addition to these components, there are a variety of types of connection that connect the above-mentioned components electrically, galvanically safe with each other, for. As soldering, plug, crimp connections, among others

The additional device used for the measuring device according to the invention, consists in particular of a mechanical stimulator, here as a vibrating device ( 7 ), which generates longitudinal and / or transverse vibrations and introduces into the component. This is externally to the electrical measurement process is a kinetic energy source. Upon contact and nipping the Schwingeinrichtungsspitze ( 8th ) on a component, for. B. cold solder joint ( 6 ) of the measuring circuit ( 5 ), the kinetic is converted into mechanical energy. This results in tensile and compressive forces which, in particular at the solder joint, cause an increased paramatersensitization and can be measured electrically. The stimulating vibrations by the additional device are changeable, controllable or adjustable in terms of amplitude and / or frequency.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 29823250 U1 [0007]
• - DE 4143546 C2 [0008]
• EP 0124761 A1 [0009]

Claims (6)

Measuring equipment suitable for laboratory, production, quality control and production, for universal, online-capable, metrological detection of quality defects in the measuring circuit integrated, mostly hidden, usually not metrologically detected or contactable vulnerabilities, inaccessible components, joints, cold solder joints o ., In simple and complex electrical and electronic circuits, with the complex impedance of a component or a measuring circuit is measured as a linear dipole and in particular complex impedance parameters, such as damping, quality and loss factor can be detected, inter alia, characterized in that an additional device available is, by means of the in a measuring operation of the complex electrical impedance of a two-terminal measuring device offset in time, simultaneously or temporarily by externally initiated, externally excited energetic stimulation of the measuring circuit or a singular component or a Weak point, such as cold solder joint, in the complex impedance parameter values in the event of a fault to cause a significant change that can be measured and evaluated by the measuring device. Measuring device according to claim 1, characterized that as a result of the combination of simultaneously more static complex Impedance measurement and energetic external excitation / modulation a change the impedance parameter is generated and detectable. Measuring device according to claim 1 or 2, characterized that the energetic action of the attachment in it There is a kinematic kinetic energy at the stimulator tip at the coupling point of the component into mechanical energy in the form of Tensile and compressive forces is converted Measuring device according to one of the preceding claims, characterized in that the stimulation amplitude and / or the stimulation frequency of the stimulator tip of the attachment can be changed or is controllable. Measuring device according to one of the preceding claims, characterized in that the energetic action of the An additional device is that a thermal energy at the Stimulator tip generated, this point at the coupling point of the component initiated and at least partly in mechanical energy in the form is transformed by expansion forces. Measuring device according to claim 5, characterized in that that the thermal energy at the stimulator tip of the attachment can be regulated and / or switched off.