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Author:Sutela, Lassi
Title:Evaluation of measuring methods for dissipative plastic materials
Publication type:Master's thesis
Publication year:2004
Pages:69      Language:   eng
Department/School:Sähkö- ja tietoliikennetekniikan osasto
Main subject:Mittaustekniikka   (S-108)
Supervisor:Wallin, Pekka
Instructor:Keskinen-Peltola, Matti
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark S80     | Archive
Keywords:change decay
ESD
dissipative
packaging material
varauksen purkuaika
dissipatiivinen
pakkausmateriaali
Abstract (eng): Electrostatic properties of materials have been studied for decades.
During last two decades integration level in electronics has increased and signal speeds have become faster.
These two factors have lead electronics industry to situation, where even more careful protection against electrostatic discharge has to be taken care of.
The properties of different assessment methods of dissipative plastic materials were compared in this study.
Surface resistivity and charge decay time were the most important measurements.
Volume resistivity measurements were not carried out, because most of specimens had insulating layers.
Modem plastic materials, which demonstrate properties against static electricity, are not homogeneous.
Surface resistivity measurement was found out to be a good fundamental method to assess materials, despite multiple decay time measurement methods.
If the surfaces of a material are insulating, the material typically get charged and will not discharge.

Charge decay time measurement is more difficult to carry out, but it gives lot of information about materials.
If charge decay time is adequate and decay curve is exponential, the material is not likely to cause risk in terms of ESD.
Multiple decay time measurement methods were studied and all of them had some challenges.
Corona charging method was the most suitable method to charge material in charge decay measurement.
In addition, triboelectric method can be used.
Most important question, when selecting the method is, does the material really get charged?
Adequate initial charge can be easily achieved with corona method.
Triboelectric method resembles actual charging situation, but sometimes it is hard to achieve measurable initial charge.
With surface resistivity and corona or triboelectric methods, it is possible to reliably assess the electrostatic properties of materials.
Right choices ensure that products do not encounter ESD from packaging materials.
Abstract (fin): Materiaalien sähköstaattisia ominaisuuksia on tutkittu vuosikymmeniä.
Viime vuosina elektroniikan integrointiasteen ja signaalinopeuksien kasvaessa laitteiden suojaus sähköstaattisia purkauksia vastaan on tullut yhä tärkeämmäksi.

Tässä tutkimuksessa on keskitytty pakkausmateriaalien sähköstaattisten ominaisuuksien mittausmenetelmien vertailuun.
Pintaresistiivisyys ja varauksen purkuaika ovat tärkeimmät menetelmät, joilla materiaaleja voidaan vertailla.
Tilavuusresistiivisyyteen ei kiinnitetty huomiota tämän tutkimuksen puitteissa, sillä useimmat tutkitut materiaalit olivat epähomogeenisiä.

Pintaresistiivisyysmittaus osoittautui hyväksi perustestiksi luokiteltaessa materiaaleja.
Jos materiaalin pinta ei johda, eivät varaukset pääse poistumaan siitä ja materiaali voi varautua.

Varauksen purkuaikamittaus on haastavampi suorittaa, kuin pintaresistiivisyysmittaus, mutta se antaa paljon tietoa materiaalin sähköstaattisista ominaisuuksista.
Jos varaukset purkautuvat riittävän nopeasti, ei materiaali aiheuta kasvanutta riskiä staattisen sähkön näkökulmasta.

Useita purkuaikamenetelmiä tutkittiin.
Kaikissa tutkituissa menetelmissä oli etunsa ja haittansa.
Koronamenetelmä osoittautui kaikkein soveltuvimmaksi varausmenetelmäksi.
Myös triboelektrinen varaus sopii varauksen purkuaikamittauksiin.
Tärkeintä on, että käytetty menetelmä todella varaa näytteen.
Muutoin mittaus voi johtaa vaaraan johtopaatokseen.

Pintaresistiivisyysmittauksella ja korona- tai triboelektrisellä varauksella suoritetulla purkuaikamittauksella voidaan luotettavasti luokitella materiaalin sähköstaattiset ominaisuudet.
Oikealla materiaalivalinnalla voidaan suojata elektroniikka pakkauksen aiheuttamalta ESD riskiltä.
ED:2004-10-21
INSSI record number: 26406
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