SIST EN 62047-12:2012

Semiconductor devices - Microelectromechanical devices - Part 12: Bending fatigue testing method of thin film materials using resonant vibration of MEMS structures

IEC 62047-12:2011 specifies a method for bending fatigue testing using resonant vibration of microscale mechanical structures of MEMS (micro-electromechanical systems) and micromachines. This standard applies to vibrating structures ranging in size from 10 μm to 1 000 μm in the plane direction and from 1 μm to 100 μm in thickness, and test materials measuring under 1 mm in length, under 1 mm in width, and between 0,1 μm and 10 μm in thickness. The main structural materials for MEMS, micromachine, etc. have special features, such as typical dimensions of a few microns, material fabrication by deposition, and test piece fabrication by means of non-mechanical machining, including photolithography. The MEMS structures often have higher fundamental resonant frequency and higher strength than macro structures. To evaluate and assure the lifetime of MEMS structures, a fatigue testing method with ultra high cycles (up to 10¹²) loadings needs to be established. The object of the test method is to evaluate the mechanical fatigue properties of microscale materials in a short time by applying high load and high cyclic frequency bending stress using resonant vibration.

Halbleiterbauelemente - Bauelemente der Mikrosystemtechnik - Teil 12: Verfahren zur Prüfung der Biege-Ermüdungsfestigkeit von Dünnschichtwerkstoffen unter Verwendung der Resonanzschwingungen bei MEMS-Strukturen

Dispositifs à semiconducteurs - Dispositifs microélectromécaniques - Partie 12: Méthode d'essai de fatigue en flexion des matériaux en couche mince utilisant les vibrations à la résonance des structures à systèmes microélectromécaniques (MEMS)

La CEI 62047-12:2011 spécifie une méthode d'essai de fatigue en flexion utilisant les vibrations à la résonance des structures mécaniques à très petite échelle des systèmes microélectromécaniques (MEMS), et des micromachines. La présente norme s'applique aux structures vibrantes dont la taille est dans la gamme allant de 10  μm à 1 000 μm dans le plan et de 1 μm à 100 μm d'épaisseur, ainsi qu'à des matériaux d'essai mesurant moins de 1 mm de longueur, moins de 1 mm de largeur et entre 0,1 μm et 10 μm d'épaisseur. Les matériaux de construction principaux pour les systèmes microélectromécaniques, les micromachines, etc., comportent des caractéristiques spéciales telles que des dimensions typiques de l'ordre de quelques microns, la fabrication des matériaux par dépôt et la fabrication d'éprouvettes d'essai par usinage non mécanique, par exemple la photolithographie. Les structures à systèmes micro-électromécaniques présentent souvent une fréquence de résonance fondamentale et une résistance supérieures à celles des macro-structures. Pour évaluer et garantir la durée de vie des structures à systèmes microélectromécaniques, on doit établir une méthode d'essai de fatigue avec des cycles de charge très élevés (jusqu'à 10¹²). Le but de la méthode d'essai est d'évaluer les propriétés de fatigue mécanique des matériaux à très petite échelle sur une courte durée en appliquant une contrainte de flexion à charge élevée et à haute fréquence cyclique en utilisant des vibrations à la résonance.

Polprevodniški elementi - Mikroelektromehanski elementi - 12. del: Metoda za preskušanje upogibne utrujenosti tankoplastnih materialov z uporabo resonančnih tresljajev struktur mikroelektromehanskih sistemov (MEMS)

Ta del IEC 62047 določa metodo za preskušanje upogibne utrujenosti z uporabo resonančnih tresljajev mikromehanskih struktur MEMS (mikroelektromehanskih sistemov) in mikrostrojev. Ta standard velja za vibrirajoče strukture v razponu velikosti od 10 μm do 1000 μm v smeri ravnine in debeline od 1 μm do 1000 μm ter za preskusne materiale, ki merijo manj kot 1 mm v dolžino, manj kot 1 mm v širino in med 0,1 μm in 10 μm v debelino. Glavni strukturni materiali za MEMS, mikrostroje itd. imajo posebne lastnosti, kot so značilna velikost nekaj mikronov, izdelava materiala z usedanjem in preskušanci, narejeni z nemehansko strojno obdelavo, vključno s fotolitografijo. Strukture MEMS imajo pogosto višjo osnovno resonančno frekvenco in višjo trdnost kot makrostrukture. Za ocenjevanje in zagotavljanje življenjske dobe struktur MEMS je treba vzpostaviti preskusno metodo utrujenosti z ultravisokimi cikli (do 1012) obremenitve. Cilj preskusne metode je v kratkem času oceniti lastnosti mehanske utrujenosti materialov na mikroravni z uporabo visokih obremenitev in visokih cikličnih frekvenc upogibne napetosti z uporabo resonančne vibracije.

General Information

• Status: Published
• Publication Date: 17-Nov-2011
• ICS: 31.080.01 - Semiconductor devices in general
• Technical Committee: I11 - Imaginarni 11
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 15-Nov-2011
• Due Date: 20-Jan-2012
• Completion Date: 18-Nov-2011
• Ref Project: EN 62047-12:2011 - Semiconductor devices - Micro-electromechanical devices - Part 12: Bending fatigue testing method of thin film materials using resonant vibration of MEMS structures

Overview

EN 62047-12:2011 (IEC 62047-12:2011) defines a standardized bending fatigue testing method for thin film materials using resonant vibration of MEMS structures. The standard targets microscale mechanical structures and test pieces produced by semiconductor/microfabrication techniques. It enables accelerated evaluation of mechanical fatigue properties under high-frequency cyclic bending loads - including ultra-high cycle testing (up to 10^12 cycles) - to support lifetime assessment and reliability of MEMS and micromachines.

Key topics and technical requirements

• Scope and size ranges: Applies to vibrating structures with in‑plane dimensions ~10 µm to 1 000 µm, thickness 1 µm to 100 µm; test materials under 1 mm length/width and 0.1 µm to 10 µm thickness.
• Test equipment: Specifies the roles and requirements for actuators, sensors, controllers and recorders capable of stable resonant vibration at controlled amplitude and frequency.
• Specimen preparation: Defines resonant property characterization and non‑mechanical fabrication (photolithography, deposition) typical for thin‑film MEMS test parts.
• Test conditions: Addresses test amplitude, load ratio, vibration frequency, waveform, test time and environment to ensure reproducible bending fatigue loading.
• Initial measurements: Requires reference (static/instantaneous) strength measurement and frequency response testing before fatigue loading.
• Test procedure and monitoring: Includes initial load application, continuous monitoring (displacement/strain or other signals), counting cycles, end‑of‑test criteria and required recorded data.
• Reporting: Specifies minimum test report contents for traceability and statistical analysis.
• Informative annexes: Practical examples (electrostatic actuation with integrated detection, external drive with strain gauge, electromagnetic out‑of‑plane drive), and theoretical/analysis guidance (Paris’ law, Weibull distribution, analysis examples).

Applications and users

This standard is used to assess MEMS thin‑film fatigue life and reliability in applications such as sensors, actuators, RF MEMS, microengines and micromirrors. Typical users include:

• MEMS designers and reliability engineers
• Semiconductor and microfabrication test laboratories
• Materials scientists studying thin‑film fatigue (e.g., silicon, polysilicon)
• QA/qualification teams for MEMS products and micromachines

EN 62047-12:2011 helps organizations implement consistent, comparable bending‑fatigue test programs to quantify lifetime, support design margins, and validate manufacturing processes.

Related standards

• IEC/EN 62047-3 (thin film standard test piece for tensile-testing)
• ISO 12107 (fatigue testing - statistical planning and analysis)

Keywords: EN 62047-12:2011, IEC 62047-12, MEMS bending fatigue testing, resonant vibration, thin film fatigue, ultra-high cycle fatigue, MEMS reliability.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Halbleiterbauelemente - Bauelemente der Mikrosystemtechnik - Teil 12: Verfahren zur Prüfung der Biege-Ermüdungsfestigkeit von Dünnschichtwerkstoffen unter Verwendung der Resonanzschwingungen bei MEMS-StrukturenDispositifs à semiconducteurs - Dispositifs microélectromécaniques - Partie 12: Méthode d'essai de fatigue en flexion des matériaux en couche mince utilisant les vibrations à la résonance des structures à systèmes microélectromécaniques (MEMS)Semiconductor devices - Microelectromechanical devices - Part 12: Bending fatigue testing method of thin film materials using resonant vibration of MEMS structures31.080.01Polprevodniški elementi (naprave) na splošnoSemiconductor devices in generalICS:Ta slovenski standard je istoveten z:EN 62047-12:2011SIST EN 62047-12:2012en01-januar-2012SIST EN 62047-12:2012SLOVENSKI
STANDARD
EUROPEAN STANDARD EN 62047-12 NORME EUROPÉENNE
EUROPÄISCHE NORM October 2011
CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung
Management Centre: Avenue Marnix 17, B - 1000 Brussels
© 2011 CENELEC -
All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62047-12:2011 E
ICS 31.080.99
English version
Semiconductor devices -
Micro-electromechanical devices -
Part 12: Bending fatigue testing method of thin film materials using resonant vibration of MEMS structures (IEC 62047-12:2011)
Dispositifs à semiconducteurs -
Dispositifs microélectromécaniques -
Partie 12: Méthode d'essai de fatigue en flexion des matériaux en couche mince utilisant les vibrations à la résonance des structures à systèmes microélectromécaniques (MEMS) (CEI 62047-12:2011)
Halbleiterbauelemente -
Bauelemente der Mikrosystemtechnik -
Teil 12: Verfahren zur Prüfung der Biege-Ermüdungsfestigkeit von Dünnschichtwerkstoffen unter Verwendung der Resonanzschwingungen bei MEMS-Strukturen (IEC 62047-12:2011)
This European Standard was approved by CENELEC on 2011-10-18. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.
The following dates are fixed: • latest date by which the document has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2012-07-18 • latest date by which the national standards conflicting with the document have to be withdrawn (dow) 2014-10-18
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights. Endorsement notice The text of the International Standard IEC 62047-12:2011 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography, the following note has to be added for the standard indicated: IEC 62047-2:2006 NOTE
Harmonized as EN 62047-2:2006 (not modified).
- 3 - EN 62047-12:2011 Annex ZA
(normative) Normative references to international publications with their corresponding European publications
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
NOTE
When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies.
Publication Year Title EN/HD Year
IEC 62047-3 2006 Semiconductor devices - Micro-electromechanical devices -
Part 3: Thin film standard test piece for tensile-testing EN 62047-3 2006
ISO 12107 - Metallic materials - Fatigue testing - Statistical planning and analysis of data - -
IEC 62047-12 Edition 1.0 2011-09 INTERNATIONAL STANDARD NORME INTERNATIONALE Semiconductor devices – Micro-electromechanical devices –
Part 12: Bending fatigue testing method of thin film materials using resonant vibration of MEMS structures
Dispositifs à semiconducteurs – Dispositifs microélectromécaniques –
Partie 12: Méthode d'essai de fatigue en flexion des matériaux en couche mince utilisant les vibrations à la résonance des structures à systèmes microélectromécaniques (MEMS)
INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE U ICS 31.080.99 PRICE CODE CODE PRIX ISBN 978-2-88912-689-7
– 2 – 62047-12  IEC:2011 CONTENTS
FOREWORD . 4 1 Scope . 6 2 Normative references . 6 3 Terms and definitions . 6 4 Test equipment . 7 4.1 General . 7 4.2 Actuator . 8 4.3 Sensor . 8 4.4 Controller . 8 4.5 Recorder . 9 4.6 Parallel testing . 9 5 Specimen . 9 5.1 General . 9 5.2 Resonant properties . 9 5.3 Test part. 9 5.4 Specimen fabrication . 9 6 Test conditions . 9 6.1 Test amplitude. 9 6.2 Load ratio . 10 6.3 Vibration frequency . 10 6.4 Waveform . 10 6.5 Test time . 10 6.6 Test environment. 10 7 Initial measurement . 10 7.1 Reference strength measurement . 10 7.2 Frequency response test . 11 8 Test . 11 8.1 General . 11 8.2 Initial load application . 11 8.3 Monitoring . 12 8.4 Counting the number of cycles . 12 8.5 End of the test . 12 8.6 Recorded data . 12 9 Test report. 12 Annex A (informative)
Example of testing using an electrostatic device with an integrated actuation component and displacement detection component . 14 Annex B (informative)
Example of testing using an external drive and a device with an integrated strain gauge for detecting displacement . 17 Annex C (informative)
Example of electromagnetic drive out-of-plane vibration test
(external drive vibration test) . 20 Annex D (informative)
Theoretical expression on fatigue life of brittle materials based on Paris’ law and Weibull distribution . 23 Annex E (informative)
Analysis examples. 27 Bibliography . 29 SIST EN 62047-12:2012

62047-12  IEC:2011 – 3 –
Figure 1 – Block diagram of the test method . 7 Figure A.1 – Microscope image of the specimen . 14 Figure A.2 – Block diagram of test equipment . 15 Figure B.1 – The specimens’ structure . 17 Figure B.2 – Block diagram of test equipment . 18 Figure C.1 – Specimen for out-of-plane vibration testing . 20 Figure C.2 – Block diagram of test equipment . 21 Figure E.1 – Example of fatigue test results for silicon materials . 27 Figure E.2 – Static strength and fatigue life of polysilicon plotted in 3D . 28
– 4 – 62047-12  IEC:2011 INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
SEMICONDUCTOR DEVICES –
MICRO-ELECTROMECHANICAL DEVICES –
Part 12: Bending fatigue testing method of thin film materials
using resonant vibration of MEMS structures
FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter. 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by independent certification bodies. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 62047-12 has been prepared by subcommittee 47F: Micro-electromechanical systems, of IEC technical committee 47: Semiconductor devices. The text of this standard is based on the following documents: FDIS Report on voting 47F/80/FDIS 47F/90/RVD
Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. SIST EN 62047-12:2012

62047-12  IEC:2011 – 5 – A list of all parts of IEC 62047 series, under the general title Semiconductor devices – Microelectromechanical devices, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the specific publication. At this date, the publication will be
• reconfirmed, • withdrawn, • replaced by a revised edition, or • amended.
– 6 – 62047-12  IEC:2011 SEMICONDUCTOR DEVICES –
MICRO-ELECTROMECHANICAL DEVICES –
Part 12: Bending fatigue testing method of thin film materials
using resonant vibration of MEMS structures
1 Scope
This part of IEC 62047 specifies a method for bending fatigue testing using resonant vibration of microscale mechanical structures of MEMS (micro-electromechanical systems) and micromachines. This standard applies to vibrating structures ranging in size from 10 µm to 1 000 µm in the plane direction and from 1 µm to 100 µm in thickness, and test materials measuring under 1 mm in length, under 1 mm in width, and between 0,1 µm and 10 µm in thickness. The main structural materials for MEMS, micromachine, etc. have special features, such as typical dimensions of a few microns, material fabrication by deposition, and test piece fabrication by means of non-mechanical machining, including photolithography. The MEMS structures often have higher fundamental resonant frequency and higher strength than macro structures. To evaluate and assure the lifetime of MEMS structures, a fatigue testing method with ultra high cycles (up to 1012) loadings needs to be established. The object of the test method is to evaluate the mechanical fatigue properties of microscale materials in a short time by applying high load and high cyclic frequency bending stress using resonant vibration. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 62047-3:2006, Semiconductor devices – Micro-electromechanical devices – Part 3: Thin film standard test piece for tensile testing ISO 12107, Metallic materials – Fatigue testing – Statistical planning and analysis of data 3 Terms and definitions
For the purposes of this document the following terms and definitions apply 3.1
amplitude one-half the algebraic difference between the maximum value and minimum value in a loading cycle 3.2
load ratio algebraic ratio of the maximum value and minimum value of the load of a cycle 3.3
S-N curve plot of stress or strain (S) against the number of cycles (N) to failure SIST EN 62047-12:2012

62047-12  IEC:2011 – 7 – 3.4
reference strength: static strength or instantaneous failure strength
3.5
instantaneous failure strength failure strength of quasi-static test or resonant vibration test at rapid amplitude growth
Key 1 Specimen 2 Test part 3 Actuator 4 Sensor 5 Controller 6 Recorder 7 Force 8 Displacement or strain 9 Amplitude and frequency Figure 1 – Block diagram of the test method 4 Test equipment 4.1 General The test equipment shall be capable of generating resonant vibration with constant amplitude and stable frequency to the test structure. A block diagram of the test equipment is shown in Figure 1. The test equipment consists of an actuator for oscillation, a sensor for amplitude detection, a controller for maintaining the resonant vibration at a constant amplitude, and a recorder for monitoring. The amplitude control method is classified as follows. a) Constant strain control Applied strain in the test part is maintained at constant. It can be applied for elastic or inductile materials. 3 1 2 8 7
4 5 6 9 IEC
2064/11 SIST EN 62047-12:2012
– 8 – 62047-12  IEC:2011 b) Constant stress control Applied stress in the test part is maintained at constant. Load monitoring and closed loop control is crucial for the method. 4.2 Actuator The actuator shall be capable of applying oscillation force of the necessary amplitude and frequencies along the required direction. Various kind of actuators can be used, e.g., electrostatic, piezoelectric, thermal, and electromagnetic actuators. The actuator may be installed in the test structure, as discussed in 5.1. 4.3 Sensor The sensor shall be capable of measuring the movement of the specimen to determine the stress amplitude (for constant stress amplitude testing) or the strain amplitude (for constant strain amplitude testing) to the test part of the specimen.
The sensor and its associated electronics shall be accurate to within 1 % of the range of the stress or strain amplitude. The sensor should measure the movement continuously, in order to maintain a constant vibration and detect failure effectively. If the specimen is an elastic material and will not show the change in the vibrating properties, however, it is permissible to measure the movement at regular time intervals. The movement is detected by measuring displacement of the test structure or the stress or strain in the test structure. Clause A.2 shows a method for detecting rotational displacement of the mass from changes in capacitance. Clause B.2 shows a method using a strain gauge integrated in the specimen. Clause C.2 shows a method for detecting displacement of the mass using a non-contact displacement gauge. 4.4 Controller The controller shall be capable of generating the oscillation signal to the actuator from the movement signal from the sensor, in order to maintain the required resonant vibration. During testing, the amplitude and frequency of the specimen shall be maintained at a constant level. One of the following methods should be applied for the specimen, depending on the vibration characteristics. a) Closed loop method The frequency and amplitude of the oscillation signal applied to the specimen shall be controlled to follow changes in the resonant frequency. In most cases, the signal applied to the actuator is generated from the movement signal of the specimen. A self-excited oscillation circuit or phase-locked loop circuit can be used as a means for maintaining the resonant frequency. An automatic gain control circuit (AGC) can also be used to maintain a constant amplitude by changing the amplitude of the oscillation signal based on the detected amplitude. b) Open loop method Elastic or inductile materials that show a linear response but no plastic deformation may be tested using an open loop method. This test may be performed by stopping at regular intervals and measuring the resonant characteristics, or by actuating the test structure from the start to the end of testing at a predetermined resonance frequency and oscillation signal amplitude. The stability of the frequency and amplitude shall be maintained throughout the test to within ± 3 % of the desired value. SIST EN 62047-12:2012

62047-12  IEC:2011 – 9 – 4.5 Recorder The test equipment shall include a recorder for collecting the “record data” indicated in 8.6.
4.6 Parallel testing The test may be conducted in parallel with a number of equipment units. In this case, steps should be taken to eliminate mutual electrical or mechanical interference among the equipment units. 5 Specimen 5.1 General The specimen shall be capable of applying a constant and high-load amplitude to the test part via resonant vibration. Examples of specific structures are shown in the Clauses A.1, B.1, and C.1. It is permissible to integrate a mechanism in the specimen for actuating or for sensing the movement of the specimen. An example of a structure integrating mechanisms for actuation and detecting amplitude is shown in Annex A.1. An example of a structure integrating a mechanism for detecting amplitude only is shown in Annex B.1. 5.2 Resonant properties The specimen shall have resonance characteristics that enable the application of the required deformation (mode of vibration) in the specific frequency (resonance frequency) of the specimen. The resonant frequency should preferably be more than 1 000 Hz, in order to obtain a large number of the cycles in a short time. The quality factor of the specimen should be more than 100, in order to obtain a large amplitude. Steps should be taken to ensure, within this resonance frequency, that the specimen will not vibrate in a vibration mode different from that used in the test. For example, there should be no other resonant modes close to the mode used for testing. 5.3 Test part The specimen shall have a test part in which stress sufficient to induce failure occurs. When the test is performed to evaluate the reliability of the actual device, the deformation in the test part at resonant vibration (in-plane and out-of-plane bending) shall be the same as that of the actual device. If only low stress can be applied to a structure similar to the actual device, a notch or another means may be introduced to concentrate the stress in the targeted section of the test part.
5.4 Specimen fabrication Refer to Clause 5 of IEC 62047-3 when manufacturing the test part of the specimen. The specimen should be fabricated by the same method as the target MEMS device for reliability evaluation is fabricated. Furthermore, the same shapes, dimensions, and multilayer film structures should be used. 6 Test conditions 6.1 Test amplitude The test amplitude should be specified from the appropriate reference strength of the specimen. The reference strength should be determined through the methods in 7.1. One of the following procedures should be chosen for determining the test amplitude during testing, based on the reference strength.
– 10 – 62047-12  IEC:2011 a) Constant amplitude of 100 % of the reference strength: to evaluate the fatigue life at a certain amplitude. b) Decrease the amplitude gradually from a high level: for obtaining an S-N curve in a short time. c) Increase the amplitude gradually from a low level: for obtaining an S-N curve when the number of test parts is limited. As a reference for determining the test amplitude, example of experimental data and analysis of fatigue testing for silicon are shown in Annex D. For details on the testing of metal materials, refer to ISO 12107. The decrease and increase step of the test amplitude for the procedures b) and c) should be selected preferably close to the standard deviation of measured reference strength. 6.2 Load ratio The load ratio of the test method can be taken to be -1, as the quality factor (Q) of the resonant vibration is high enough (10 or more) to achieve an amplitude too high to apply by (quasi-)static testing methods.
6.3 Vibration frequency The frequency shall be the resonant mode at which the test part is in the required stress state specified in 5.3, or a frequency close to it. 6.4 Waveform The waveform of the displacement of the specimen and the stress and strain of the test part can be regarded as sinusoidal, irrespective of the actuating waveform 6.5 Test time The test time shall be specified as the time at which the test ends, even if the specimen has not failed by that time. The test time can be determined as the number of the test cycles, based on the vibration frequency. For tests conducted on materials with lifetime characteristics which are frequency-independent, such as silicon, the test cycles are chosen as the stress cycles applied on the actual devices in their lifetimes. See Annex D.
6.6 Test environment The test environment should be maintained at a constant temperature and humidity. 7 Initial measurement 7.1 Reference strength measurement The reference strength shall be measured prior to the fatigue test. Specimens used for measurement of the reference strength should be made of the same materials, and by the same processes, as the test part to be tested. Care shall be taken when using a specimen of a different shape. If such a specimen is used, it should show the same failure mode, and the size effect on the measured strength should be considered. The reference strength should be determined using one of the following tests.
a) Quasi-static test SIST EN 62047-12:2012

62047-12  IEC:2011 – 11 – The failure strength measured by conducting quasi-static testing is set as the reference strength. b) Instantaneous fatigue test The maximum amplitude in the instantaneous fatigue test is set as the reference strength. In this test, the amplitude is rapidly increased up to the point of specimen failure by the same method used for the fatigue test. This method may be chosen when it is difficult to use a specimen of a different shape, or when it is difficult to apply a static load.
c) Stress analysis The reference strength is determined using either simulation or theoretical analysis. This method can be chosen when a reference strength is difficult to determine experimentally. The amplitude at which the maximum stress in the specimen reaches the failure strength is set as the reference strength. The failure strength can be taken from published papers or other available data. The reported strength should be chosen carefully, as some materials have size effect in failure strength and environmental effects under variable temperatures, humidity levels, and so on. It is thus desirable to refer to the strength values in the literature in order to keep conditions as close as possible to those in the life test to be conducted. Given the large variation in the strength of brittle materials such as single crystal silicon, it is preferable to obtain strength data for no less than 10 specimens when measuring the reference strength experimentally, and to adopt a statistically processed value (for example, 50 % failure stress from Weibull analysis or an arithmetical average) as the reference for stress or strain in the resonant oscillation test. 7.2 Frequency response test The resonant properties of the specimens shall be measured prior to the fatigue test. When the resonant properties vary among specimens and the controller needs tuning, the resonant properties of all of the specimens should be measured. The frequency response test is used to measure the resonant properties. The oscillation signal is applied from a function generator and the frequency of the signal is swept around the expected resonant properties to find the actual resonant frequency. The load applied in this response test shall be small enough to ensure that the measurements for the fatigue test are unaffected. If the effect cannot be ignored, the number of load cycles applied in this response test should preferably be added to the fatigue test data. 8 Test 8
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