Pure-spacesuited materials
Pure-spacesuited materials test and classification procedures around
the industry with the structure of manufacturing plants for konta
minationsempfindliche mikrosysteme to support, are needed purity-fair
reason and structure materials. World-wide no material lists are
available, so that with the selection of suitable materials to optical
and scientifically not secured criteria one pays attention purely.
With a standardized testing method for the evaluation of the pure
space fitness of materials one works against to this circumstance. 1
introduction the claims of quality to all products constantly rise. A
constantly growing number of industries and their products need
therefore a purity-fair manufacturing. With the "pure manufacturing"
it is necessary to control all product-relevant contamination factors.Particularly within ranges like the semiconductor industry, the
foodstuffs industry or the pharmaceutical industry a particularly high
value comes to the avoidance of individual contamination. Means of
production, which are used into pure manufacturing, carry often
substantial for the contamination of the "pure manufacturing" those
procedures, which lead to the generation of particle emission
procedures at means of production, can to friction and
schwingungsvorgaenge be attributed. To emphasize is:: Friction
procedures, which are caused by the relative motion of the means of
production surfaces, possess the by far highest portion. For the
generation of particles on technical surfaces of friction partners
existed at present still no scientifically founded model conception,
which permits it, the material selection for "pure manufacturing"
already in the apron of meeting during the means of production
development.In the area of the clearing-up of connections between technical
characteristics of combinations of material and the generation of
contamination, in particular those the airborne particles at means of
production, no research work is to be in-grouped bekannt.Um the
contamination behavior of basic materials or surface coatings, must a
procedure for determining the pure space fitness by combinations of
material be compiled. above all to the emission of airborne, mikroner
and/or submikroner particles a special meaning is attached to 2
prioritization of the kinds of contamination apart from the
electrostatic contamination behavior or the delivery of easily
volatile organic materials. If the source of particle "humans" remains
unconsidered, latter process has the largest influence on the
pollution of the product (with approximately 30 % to 40 % portion of
all, unwanted contamination arising in the pure area).A representatively accomplished inquiry with approximately 270
companies resulted in that the partikelfoermigen contamination takes
the highest value regarding the research need:: Two thirds of all
demands on the materials cover the particle poverty or particle
liberty. Linked with the particle emission closely, the surface
quality of assigned materials (fig. 1) stands. Particles emitted by
means of production develop due to material oscillations or relative
motions of at least two together rubbing materials. With these induced
friction pairings of means of production components the surface
systems of means of production take to crucial influence on the
generation of particle. 3 contentwise objective 3,1 developing a test
procedure around the individual emission behavior of different
combinations of material to clear up, is developed a standardized test
procedure.During the practical conversion a material test stand serves for the
contamination-free under search of materials for the pure space
employment. The development of a scientifically founded test procedure
ensures - reproductibility, - the comparability, - security and - to
interpretation of the results of measurement. 3.2 evaluation and
classifying scheme for evaluating and classifying gewon the nenen
measuring data must be compiled and used evaluation mechanisms. Here
can be partly fallen back to guideline and standard works from the
semiconductor and clean-room technology, already existing. The
evaluation algorithms for the measuring data are to point clearly the
suitability out of the different combinations of material for the
employment within pure ranges. 3.3 optimizing combinations of material the proceeding divided into -
actual condition analysis (first determination of the contamination
condition), - the modification of the combination of material
(optimization of the Tribosystems) and - verification analysis
(determination of the contamination condition renewed) dividing
permits a systematic advancement of the combinations of material to
the purity-relevant requirements. With the regarding of the airborne
individual contamination statements about the suitability of the
combinations of material for existing air categories of purity can be
met, since in the internationally recognized air purity standards only
to this kind of contamination is referred. This circumstance increases
the national and international acceptance of the test procedure and
their results crucially. 4 process development nearly all movement
procedures at production plants leads to friction procedures between
two materials.The friction again is the most frequent cause for the particle
emergence. In order to make this scientifically seizable, the particle
emissions must be seized and evaluated instrumentation. First step
here is identifying the Hauptemissionsquelle(n) at material
construction units or components. In order if possible few foreign
influences on the result of measurement of the detected sources of
main mission to received, as much as possible sources of influence of
noise are to be eliminated. That succeeds to the friction pairing
place from the material construction unit at the best one with
extracting and separating. For this the friction pairing place in a
test stand on standardized, reproducible laboratory conditions must be
placed behind (fig. 2).The procedure for the evaluation of the purity quality of the examined
combinations of material is two statements liefern::• in which air
categories of purity (following international sets of rules for the
evaluation of the air purity) to know "separated" material mating is
used, und• in what respect is the results of the investigations on
laboratory conditions to material construction unit/components
transferably. Material construction units and components are examined
after the established proceeding of the VDI 2083 sheet 8 "pure space
fitness by operational funds" on their pure space fitness. This
proceeding is appropriate for the evaluation of complex construction
units. With the attempt to examine individual combinations of material
this procedure fails.Transfer the results to material construction units after the friction
partners identified and into a Tribosystem in the laboratory test
stand are transferred, extents of utilization are adapted to typical
load conditions of the material construction units. Classification
measurements and evaluations find after VDI 2083 sheet 8 (material
construction unit) as well as the classification model for
combinations of material with the load universe of three
representative extents of utilization. In order to determine the
transferability of the differently won classification results, a model
must be developed. It can be provided however only in a second step,
if the classification model were established before for the evaluation
of the pure space fitness of combinations of material in test stands.
All obtained measured values and statements are to be confirmed with
suitable statistic procedures. 5 conceiving a material test stand 5.1 friction procedures the friction between two bodies can be realized
in principle by the three following procedures (fig. 3 and picture 4)
with the "spherical washer test" is pressed a ball against the front
surface of a disk. The contact point is punctiform, the ball is fix
with the "disk disk test" a swivelling stored disk laterally to the
drive disk is advanced and unreels on this. The contact point is
linienfoermig, both surfaces is curved at the contact point. With the
"role disk test" a role (for example high-grade steel or PA6-Rolle) is
pressed on the face of a disk, which is provided with the coating
which can be examined. The procedure is used for the investigation of
linings or coatings, on which in the material case a role runs off.
The "role disk test" is used for example of the examination of a pure
space floor mat, on which roll-claimant cars run off. 5.2 attempt principle the "spherical washer test" frequently into
literature and practice is used there, are present for this extensive
data records for correlation with the generation of particle. A
further advantage of the test is in the fact that a punctiform contact
point between the materials is present. Since thus a high
standardizableness exists, the "spherical washer procedure" is
consulted for the following views. Rotates a test disk with the
frequency f under a ball of the diameter D, which is pressed with the
normal force FN with a radius r on the disk. At the contact point of
ball and disk it comes to a material removal, which is accompanied by
a particle emission. It is formed a wear trace.The characteristics both the wear trace and the contact point can be
consulted in dependence of the detectable load sizes at material
components (pressing surface, laufstrecke, multiple load of stages)
for the evaluation and fine differentiation. 5.3 identifying the
relevant parameters with a "spherical washer test" represents the
inspection pieces involved (ball, disk) a wear system. It can be
described by a parameter set. For the attempts accomplished here the
relevant parameters of the wear system do not result following DIN
50320 (old) as in fig. 5 gezeigt.In the literature are present data,
whose article the individual emission of friction pairings or the
linkage of tribologischen sizes with an observed particle emission is.
In DIN 50324 (old) an interlaboratory test is described, in which by
means of the "spherical washer test" high-grade steel mating is
examined.The inputs used there served the preliminary tests as starting point
for Vorversuche.In the dependence of the examined characteristics
(particle emission, tribologische sizes) of the normal force were
examined and the temporal development during a longer period seized.
the conception of a test stand shows 5.4 shifting of the test stand
concept fig. 6 after the "spherical washer test", with which the
requirements at the pure space and purity fitness of the test stand
must be kept. 5.5 integrating the particle investigations with the
determination of the Tribo characteristics of parallel to the
investigation of the particle emission is determined tribologische
characteristics. For the confrontation of the results as reference
basis the particle emission is used. From the measured values of the
individual particle channels (0.2 µm; 0,3 µm; 0,5 µm and 5.0 µm) the
size of "particle volume" can be derived.The tribologischen characteristics are referred individually and in
compound form (when derived sizes such as trace volumes) to this size.
Thus the connection of the tribologischen characteristics and the
particle emission values can be judged. 6 classification model for
combinations of material a crucial goal is it to observe and
characterize the development of the particle emission during the
tribologischen load. The used optical particle counters supply the
particle measured values in differential representation, that means as
counting events per gate time or measuring volume interval. In
preliminary tests a very unsteady behavior of the measured value
development resulted in the case of the diagram of the particle
measured values over the number of revolutions, so that the measured
values in this form were unsuitable as basis for a characterisation
(fig. 7).While the first revolution of the test ball on the test disk, the ball
on a so far unaffected laufstrecke runs off, so that a small particle
emission takes place. During the subsequent revolution the ball on a
laufstrecke already loaded runs off, so that increased particle
emissions are the result. This effect continues with the subsequent
revolutions in each case and explains the observed unstable behavior
of the emission values over the total time. This circumstances lead to
the fact that the condition for an evaluation with the student t and
Poisson statistics - as this demands the VDI 2083 sheet 8 - is no more
fulfilled be-generally a tendentious rise of the measured values with
the number of revolutions to observe (see fig. 7). If now all
generated particles up to a discrete number of revolutions are added,
this corresponds integrals to a representation of the particle
measured values.The resulting curves show a constant process (fig. 8) in this
representation. With the help of integrals the representation graphs
can be produced, those as basis for the characterisation of the
particle emission serve to the explanation of the observed increase of
the emission values over the time are assumed during the first
revolution of the combination of material particles are already
produced as abrasives. While the combination of material (together
with the before produced particles) causes still faster further
particles for the subsequent revolution, so that an avalanche effect
takes place. Mathematically one tries to represent the avalanche-like
rise of the particle emission with an exponential beginning:: After an
approximation of the particle emission graphs by means of nonlinear
involution, cumulated, the curves can be mathematically accurately
further regarded.The parameters A and b and/or the pair (a/b) of the regression curves
represent a yardstick for the emission rate and thus the pure space
fitness of the regarded Werkstoffpaarung.Da the number of generated
particles directly with the number of revolutions, only however in
subordinated measure with the applied time are connected, as new
control variable in place of the gate time the number of the
revolutions are consulted. After converting the limit values of the
maximally permissible particle numbers for the individual air
categories of purity according to DIN EN ISO 14644-1 in dependence of
the numbers of revolutions, an air category of purity diagram adapted
to the problem (fig. 9) results. During illustration of the summed
particle values by means of regression curves these always cut the
border straight lines of the air categories of purity.In order to reduce on the one hand the pair (a/b) of the regression
curves to an individual parameter, and the moreover one a clear
statement about the pure space fitness of the regarded combination of
material too received, is necessary the definition on a firm number of
revolutions. Since in the represented example the examined combination
of material during the reference revolution of N = 500 between the
limit value straight lines of the air categories of purity ISO Class 5
and ISO Class 6 lie, this combination of material can be used secured
in pure areas of the ISO Class 6.7 advantages of the classification procedure in the following one are
combined the advantages of the classification model into the
evaluation of the pure space fitness of arbitrary combinations of
material:: 8 view in the further research becomes above all the
reciprocal effect relationship between classification results at
material construction units - how these were classified according to
the VDI 2083 sheet 8 - and on combinations of material in laboratory
test stands "separated" compiled.