7/28/2019 Asif 4
1/3
9781467322409/12/$31.00 2012 IEEE 161 35th Int. Spring Seminar on Electronics Technology
Electron Beam Welding of MicroHousings with Dissimilar Metals for
Electronic Circuits
M. Steinhauser, C. Krbs, R. Bauer
University of Applied Sciences Dresden, Hochschule fr Technik und Wirtschaft (HTW),
Faculty of Engineering, Dresden, Germany
Abstract: The Electron beam technology with its electromagnetic lenses enable the inertialesslydeflection and focusing of the beam and gives a lot of possibilities for welding and modification ofdifferent materials. This paper and the poster shows selected results of research investigations onthermal electron beam processes of HTW Dresden. The first part handles with the influences of theheat-input in the weld zone. The second part shows results of investigations to weld 16 electronic-housings at the same time by using the fast beam deflection as multi-weld technology.
1. INTRODUCTION
In times of energy efficiency are the economical
use of resources and the substitution of strategic
materials one of the important goals for research
investigations. New combinations of conductor- and
lightweight materials are increasingly interesting for
electrical-, automobile, medicine- and aviation
industry [1].
One strategy to reach these goals is the
combination of dissimilar metals to get the right
characteristics in the respective area. With the most
state of the art welding technologies this joints are not
producible in the required quality standard. Theelectron beam with its inimitable properties
accommodates great procedural advantages in this
section.
2. HEAT INPUT OF ELECTRON BEAM WELDING
The need for miniaturisation of electrical andelectronic assemblies leads in high requirements for
welding technology. Especially the space between
housing and the electronic circuit shows great
potentials for optimizing [2]. With a lower heat input
by the welding process the gap between housing and
electric circuit can be reduced to a minimum, so the
size of the housing can be considerably smaller.
To measure and characterise the chronological
sequence and the peak temperatures by welding with
the electron beam some basic experiments have been
made. In figure 1 you see the experimental setup of
the tests. For a plate thickness of 1 mm a 2-Dimensional thermal conduction may be adopted.
Fig. 1. Experimental setup for heat measurements.
7/28/2019 Asif 4
2/3
9781467322409/12/$31.00 2012 IEEE 162 35th Int. Spring Seminar on Electronics Technology
Fig. 2. Heat input as function of time and distance for
different materials.
The different thermal conductance of the materials
leads to diverging temperatures in the near of the
weld. This is the important criterion for the spacebetween housing and electrical circle.
The next topic presents selected results of welding
experiments at HTW Dresden.
For a plate thickness of 1 mm a 2-Dimensional
thermal conduction may be adopted, but for higher
thickness another experimental setup is needed.
3. ELECTRON BEAM WELDING OF HOUSINGSTYPE TO39
One of the great advantages of the electron-beam-technology is the inertialessly deflection and focusing
of the beam. This feature enables special joining
strategies which cannot be achieved by conventionally
welding processes [1] (Figure 3).
In the following chapter this will be shown on the
example of welding a vacuum-closed TO39-Housing.
Fig. 3. Multi process electron beam technologies.
The solution of this task made in several process
stages. At the first step the weld will be generated by
affect the housing in a circle with the CNC-
Manipulator under the idle electron beam. Theproblem of this solution is the uneven shrinking of the
hot weld, which leads into weld imperfections like
gaps, gas pores and cracks and also into long weld
intervals.
One way to solve this problem is the use of the fast
beam deflection. With electromagnetic lenses the
beam will deflect between three different points of the
housing. With modulation of the dwell time at thepoints three simultaneous weld baths can be created.
With a continuous geometrical displacement of the
coordinates of the points a closed weld seam will begenerated (Figure 4 left picture). The complete weld
process take part in one second, the weld intervals are
minimized.
An alternative by using the fast beam deflection is
the combination with the CNC-Maniplulator of the
electron beam facility. The beam deflection create
simultaneous 16 different weld baths on 16 housings,
the CNC Manipulator affect the housing in a circle
function (Figure 4 right picture).
Fig. 4. 3 beam technology (l.);12 beam technology (r.).
7/28/2019 Asif 4
3/3
9781467322409/12/$31.00 2012 IEEE 163 35th Int. Spring Seminar on Electronics Technology
A further aim is the weld of the 16 housings at thesame time in combination with the named three weld
bath strategy. For this investigation a huge
programming effort for the fast beam deflection is
needed. First trials have shown some problems with
an overshooting of the deflection amplifiers in cause
of the high deflection speed and the electromagneticinertia of the commonly used deflection-amplifier. At
the moment the latest deflection amplifiers on market
will be installed on the HTW E-beam facility. With
this new technology the problems will be solved.
4. WELDING OF DISSIMILARMETALS
One of the great advantages of the electron beamtechnology is the inertialessly deflection of the beam
by using electromagnetical fields. With this
technology open up new welding fields for the joining
of dissimilar metals like Titan-Aluminum, Steel-Aluminum or Copper-Aluminum. This material-
combinations offers new improved properties for
lightweight constructions, electrical contacting or
corrosion resistance by simultaneously reduced
production costs.
In course of the high prices of copper on market it
is planed to substitute this material with aluminum.
This courses in losses by the electrical resistance but
there is a great potential by reducing the vehicle mass.
A weak point of aluminum is the bad accessibility on
copper.The different position in the PSE leads into a lot of
different material properties, which are negative effect
the joining process and the fatique resistance. One
alternative to join this material combination is the
electron beam welding.
The possibility to deflect the beam with very high
frequenzies and the Joining in the high vacuum paving
the way to the creation of new and innovative process
technologies to affect the weld bath, which arte not
reachable by the common joining technologies. At the
electron beam laboratory of HTW Dresden somesuccessfully trials are made. The focus of this Project
lays on the specific investigations to innovative
electron beam joining technologies, the metallurgical
and mechanical behavior of the joining, the
metallurgical preparation and the long time stability.
The main goal is to reach strength conditions in the
welding zone in relation to aluminum.
First trials to join the two materials by welding
leads into not satisfactory results. The forming of
intermetallic phases induce into low mechanical
strength properties. The joint, a macrograph and a
REM-Picture are shown in figure 5 and 6.
Fig. 5. Electron beam weld of copper and aluminium.
Al 99,5 Cu-DHP
WEZ Al
1 mm
Mischzone
Al 99,5 Cu-DHP
WEZ Al
1 mm
Mischzone
Al 99,5Al 99,5 Cu-DHPCu-DHP
WEZ AlWEZ Al
1 mm1 mm
MischzoneMischzone
Fig. 6. Macrograph of the joint (l.);REM Picture (r.).
A new and innovative way to join this different
materials is the application of new electron beam
technologys (Fig. 3). By using one of the shown
Multi-process technologies a joining with a good
mechanical behaviour is created. With a combination
of the advantages of welding and brazing thethickness of the intermetallic phases is reduced up to
10 micron.
Fig. 7. Micrograph of the innovative Cu-Al-Joint.
REFERENCES
[1] Schiller, Heisig, Panzer: Elektronenstrahltechnik,Verlag Technik Berlin, 1995.
[2] Krbs, Schulze: Trends und Entwicklungen in derElektronenstrahltechnik, Vortrag zum 2. Tag derForschung, HTW Dresden 2011.
Top Related