DE3240540A1 - Method and apparatus for high-temperature soldering and brazing - Google Patents

Abstract

The invention relates to a method and an apparatus for high-temperature soldering and brazing in which the components to be joined (joining members) are fixed, filler metal is introduced between these joining members and heat is supplied to this filler metal. However, the invention can also be applied to any other field in which a thermal joining process can result in defects which can adversely affect the strength of the subsequent joint. The object of the invention, in high-temperature soldering and brazing and also in other thermal joining processes, is to avoid to the greatest possible extent defects in the area of the soldering/brazing joint or in the joining area. The invention consists in the fact that a pulsed sonic output with frequency, amplitude and pulse duration predetermined or predeterminable in accordance with the features of the entire system is superimposed on the joining process and the action of the sonic output on the soldering/brazing joint is monitored, and that the monitored data is utilised for setting the data of the pulsed sonic output. A circuit diagram of an apparatus for carrying out the method according to the invention is shown in Fig. 1. <IMAGE>

Description

Process and device for high temperature and

Brazing.

The invention relates to a method and a device for high temperature and brazing, in which the components to be connected (parts to be joined) are fixed and brazing material is introduced between these parts to be joined and heat is supplied to them.

Although main area of application of the invention soldering processes at higher Temperatures are, however, the invention is also applicable to any other field, on which a thermal joining process can result in errors, such as the strength can adversely affect the subsequent connection.

The high temperature soldering takes place without flux in a vacuum or in ehutzgas. It is particularly suitable for joining high temperature resistant materials, such as nickel rudder cobalt base alloys. Here are the parts to be joined in ovens or inductively heated to temperatures that are sometimes 10000 C and higher. That added in the form of pastes, powders, foils or - bti hard soldering - molded parts Solder melts, penetrates between the parts and connects them at the joint Cooling down. As a rule, the base material does not melt.

With high-temperature soldering, manufacturing errors can be found in many cases do not avoid. These consist mainly of brittle components in the area the seam (silicides, borides), voluminous gas inclusions (pores) as a result of insufficient Degassing and binding defects insufficient wetting as a result of fading Oxide layers on the parts to be joined.

For example, those with similar high-temperature solders based on Ni Soldered superlettings only a proportionately due to the resulting brittle phases low static and dynamic strength. This decrease in strength is intensified due to imperfections that occur if the soldering temperature is not adhered to exactly.

Here, in particular, binding defects and voluminous defects (e.g. voids) significant. The brittle phases (silicides, borides, phosphites) caused by the melting point lowering Admixtures (Si, B, P,) arise in the solder, and this in particular reduces the bonding errors the dynamic properties. This is proven by studies on long-term strength behavior of HTL connections, taking into account in addition to the static long-term test the creep behavior in particular the disruption phenomena in the fatigue test and detect the first crack formation in the over-seam area (cf. "material testing" 19 (1977) 12. S. 509/512 "Sound emission from high temperature solder connections under increased temperature and exposure "by B. Wielage, H. -A. Grostack and H. Lange).

So far, it has been very costly measures, e.g. post-heat treatments lasting several hours (20 hours at 10009 - 11000 C and more), required even a slight Achieve improvement in quality.-At annealing temperatures of 10,000 C and more the brittle phases are "molded in". The mechanical properties of the soldered seam are improved by this, but it reduces the strength of the base material. In addition, this time-consuming and expensive post-heat treatment can be used for larger ones Components can only be used to a limited extent and cannot avoid binding defects or pores.

The use introduced into soft soldering in operational practice of performance sound is associated with some major drawbacks that its So far it has been used in soldering processes at higher temperatures and in the soldering of components have ruled out. With the application of power sound known for soft soldering during high-temperature soldering, pink resonance shifts occur. In addition, the Risk of fatigue in the highly heated parts to be joined. In addition, there was an excessive Increased removal of the base material at the interface with the solder as a result of the occurrence standing waves, which result in a sharp, localized stress distribution had. The different tasks involved in high temperature and brazing for the simultaneously running processes such as degassing on the one hand and beginning Nucleation that should not be exposed to fatigue, on the other hand, are with the sound technology known for soft soldering cannot be solved.

The invention has the object of providing a method and to create a device which makes it possible to use in high temperature and brazing Avoid imperfections in the area of the soldered seam.

The method according to the invention consists in that as soon as the solder material has reached the molten state, pulsed power sound with accordingly the properties of the overall system specified or

Specifiable frequency, amplitude and pulse duration superimposed on the joining process and the power sound effect on the soldering scene is monitored and that the monitoring data used for setting the data of the pulsed power sound.

Further features of the invention are the subject matter of the invention. i Through the idea of application on which the invention is based An ultrasound that can be adapted to the soldering process is not only possible for the first time been, in high-temperature and brazing connections with significantly lower To create error frequency and increased strength, probe moreover - at the same time still to control the soldering process and thus the strict limits that have to be complied with up to now for the process (composition of the materials involved, preparation of parts to be joined; Positioning, vacuum, energy input, subsequent heat treatment), to ensure a more reliable and energy-efficient application.

The invention is described below with reference to the drawings explained. 1: a block diagram of a device for exercising the method according to the invention and FIGS. 2s to 2c: Cross-section images of soldered seams of a Nickel-based alloy.

The procedure described below is based on the principle Manufacturing defects @ in high temperature soldering, such as brittle phases, pores, lu @ xer, bonding defects among other things by Lelst-bngsschali, which is superimposed on the actual joining process, to avoid and thereby to increase the strength of the connection.

The two to; binding components la and 16 are first fixed. Then solder material is applied to the parts to be joined (powder, paste, molded parts).

The actual soldering process then begins with the supply of heat. As soon the solder has reached the molten state, the device according to Fig. 1 in effect.

In the exemplary embodiment shown, this has a generator 3 for pulsed power sound adjustable frequency content, adjustable amplitude, Pulse shape, pulse train and pulse duration. This stimulates an electro-mechanical Converter 4, which converts the electrical impulses into elastic (sound) impulses. A mechanical transformer is used to introduce the pulsed power sound (Sonotrode) 5 for power amplification and a coupling piece connected downstream of this 6, e.g. a part or a screw connection, which reduces the vibration below the desired Angle initiates in the components la, lb.

For monitoring the effect of the power noise in the soldering gap a monitoring device 7 is provided. This can be an optical one Acting monitoring device in the form of an interferometer according to Michelson, which the deflection of the parts to be joined is detected or by an acoustic monitoring device, which by means of introduced high-frequency measuring ultrasound the acoustic data (Impedance, reflection, absorption) monitored in the area of the joining zone and thus a direct information about the condition of the solder (degassing, freedom from defects) and the Base material (fatigue) supplies. To the output of the monitoring device is a control device (8a) for the generator 3 and a control device Bb switched on for the soldering process.

With complex shaped solder gaps it may be necessary that the Component lb also vibrates, e.g. in a different type of wave. In such cases the device would have an additional generator 3 with converter 4 and possibly have a mechanical transformer 5 and a coupling piece 6 for the component lb.

Further modifications of the device illustrated in FIG. 1 are possible, for example the sound transducer 4 can act on the component without contact.

When the solder has reached the molten state, means are used the device of Fig. 1 or one according to the respective requirements of the soldering process modified device pulsed power sound of a given Frequency content and specified amplitude, pulse shape, pulse train and pulse duration introduced into the joining zone. The effect of the power sound in the soldering gap is monitored by the monitoring device 7, be it optically by detecting the Deflection of the parts to be joined, be it acoustically by determining impedance, reflection, Absorption.

The monitoring device 7 can thus provide direct information on the condition of the solder (degassing, freedom from defects) and the base material (fatigue) deliver which are returned to the generator 3 via the control device 8a is used to correct the performance sound data in order to optimize it. If the joining zone has reached the desired state, the control device 8b also controls the soldering process, e.g. switched off.

The ultrasonic transmitter 3, 4 is able to transmit several frequencies Generate preselectable amplitudes, which by modulation to impulses with preselectable form, duration and sequence can be reshaped.

The advance made possible by the invention is substantial based on: -The possible variation in frequency, the amplitude and the duration allow the entire system including the Component with its temperature gradient to the required conditions of the To adapt the soldering process.

-The simultaneous work with several frequencies can otherwise In the case of resonance operation, fixed voltage distribution, which means only certain areas the joining zone are stressed to influence.

As long as the impulses are shorter than twice the component length this location dependency can largely be resolved. This creates an even Stress on the solder-it achieved and thus an almost complete freedom from defects Above all, however, overstressing of the highly heated base material is avoided.

-The variance of frequency and amplitude allows adaptation to the different phases of the soldering process.

The possibilities outlined above are the prerequisites for a successful effect of the ultrasound on the joining zone with high temperature and Brazing, with the following major improvements to the brazing process itself: -The Otherwise common defects, such as pores, lack of bonding, brittle phases, etc., can be clearly identified can be reduced, as can be seen in FIGS. 2a to 2c. These show cross-slack deviations of solder seams, which in FIGS. 2a and 2b according to the prior art, that is without Effect of performance noise at a soldering temperature of 11900 C with LNi5 as Solder powder and NiCr20TiAl are produced as the base material, with the solder seam 2a a heat treatment at 7100 C / cooling in air while has been subjected to a duration of 16 hours, while the solder seam according to Fig.

2b an additional heat treatment at 11000 C / cooling in air for a period of 20 hours.

The soldered seam L shown in Fig. 2c is made with the same base material, the same solder powder and made at the same soldering temperature as the soldered seams according to Fig.

2a and 2b, but according to the invention with the action of power sound pulses (Amplitude max = 1 µm, center frequency = 20 kHz) and without subsequent heat treatment. In FIG. 2a, a brittle phase band Sb can be seen in the central area of the soldered seam L, which is no longer present in the soldered seam L according to FIG. 2b, the soldered seam but still has pores and binding defects that occur in the soldered seam L between the Base material areas Gw according to FIG. 2c are missing.

-As a result of the absence of defects in the soldered seam when using the invention the strength of the connection increases.

-This means that the soldering time is a fraction of the previous time reducing, which reduces the unfavorable effect of the soldering process on the base material can be reduced (typical value: 1: 5).

-The conventional work to shape the brittle phases and the elaborate necessary to restore the P-round material properties Post-warming treatment can be omitted.

-The soldering gap can be widened (typical value 1: 3) the requirements for the production preparation of the components can be reduced.

-The higher freedom from defects allows the use of cheaper solder materials. When soldering nickel-based materials, solder of a similar type can be successful can be used so that the expensive gold solders can be omitted.

This results in significant savings in energy, material and manufacturing costs.

L e r s e i t e

Claims (16)

Claims: 1. method for high temperature and hard soldering, in which the components to be connected (parts to be joined) are fixed and soldering material between these parts to be joined introduced and this heat is supplied, characterized in that, as soon as the soldering material (2) has reached the molten state, pulsed power sound with predefined or predefinable according to the properties of the overall system Frequency, amplitude and pulse duration superimposed on the joining process and the impact of power noise on the soldering zone is monitored and that the monitoring data for the setting the data of the pulsed power sound can be used. 2. The method according to claim 1, characterized in that the soldering process is controlled by means of the monitoring data. 3. The method according to claim 1 and / or 2, characterized in that the pulsed performance sound by superimposing several different frequencies is generated with different, controllable amplitude. 4. The method according to at least one of the preceding claims, characterized characterized in that the Schluingungsrichtung of the power sound by mechanical Amplifier and components (4) is specified. 5. The method according to at least one of the preceding claims, characterized characterized in that the introduction of the performance sound takes place without contact. 6. The method according to at least one of the preceding claims, characterized in that all the components involved in the joining process (la, lb) by means of of the pulsed power sound are made to vibrate. 7. The method according to at least one of the preceding claims, in particular claim 6, characterized in that pulsed power sound with different wave modes are introduced into the components involved in the joining process will. 8. The method according to at least one of the preceding claims, characterized in that the soldering zone is monitored by means of high-frequency measuring ultrasound in relation to the acoustic data. 9. The method according to claim 8, characterized by the monitoring the soldering zone by detecting the deflection of the parts to be joined using a Michelson interferometer. 10. Device for high temperature and brazing with a fixing device for the components to be connected (parts to be joined) and a heating device for the soldering material introduced between these parts to be joined, identified by a Generator (3) for pulsed power sound with adjustable frequency content and / or adjustable amplitude, pulse shape, pulse train and pulse duration and a monitoring device (7) for monitoring the status data in the area of the joining zone, their measurement data for Setting of the power sound generator (3) can be used. 11. The device according to claim 10, characterized by tion (7) connected control device (8a) for controlling the power sound generator (3) with regard to frequency content, amplitude, pulse shape, pulse train and / or pulse duration. 12. The device according to claim 10 and / or 11, characterized by a control device connected to a signal output of the monitoring device (7) (8a) to control the soldering process. 13. Device according to at least one of the preceding claims 10-12, characterized by a mechanical downstream of the generator Amplifier (5) and at least one downstream coupling piece (6) for the Specification of the wave type and the direction of vibration of the power sound. 14. Device according to at least one of the preceding claims 10-13, characterized by an optical monitoring device (7), e.g. a Michelson interferometer to detect the deflection of the Parts to be joined. 15. Device according to at least one of claims 10-13, characterized by a monitoring device (7) for introducing high-frequency measuring ultrasound in the area of the joining zone and to analyze this ultrasound with respect to the acoustic data (impedance, reflection, absorption) in the joining zone. 16. Device according to at least one of the preceding claims 10 - 15, each characterized by a separate power sound generator (3) with downstream amplifier and coupling components (4 - 5) for each joining part (la, lb).