IEC 62047 13 Edition 1 0 2012 02 INTERNATIONAL STANDARD NORME INTERNATIONALE Semiconductor devices – Micro electromechanical devices – Part 13 Bend and shear type test methods of measuring adhesive st[.]
General
This standard specifies the adhesive testing methods between a columnar test piece (see
A columnar test piece is subjected to displacement or force at a constant speed to measure the adhesive strength between the test piece and substrate, with delamination force being recorded A tapered knife edge is used as the loading tool, and the angle of the knife edge is adjusted based on the different loading types employed in measuring adhesive strength.
When measuring adhesive bend strength using a bending force on a columnar test piece, the loading tool's knife edge is positioned at an angle directed upwards against the test piece, facilitating easier alignment for point load application It is important to note that this bend type test is not purely bending, as it also involves a compression component at the columnar root, which increases with a higher contact angle of the knife edge To minimize the impact of this compression component, the contact angle (θ b ) should be maintained between 10° and 20°.
To accurately measure adhesive shear strength using a shear type test, a line load must be applied parallel to the lateral face of a columnar test piece, necessitating a precise alignment system for the loading tool The knife edge can also be angled downward against the test piece to reduce bending stress, with an allowable angle error (θ s) between 0° and 15° It's important to note that test results from bend type tests are influenced by the aspect ratio (l c /D), particularly when it is below 1.2 Additionally, columnar test pieces with an aspect ratio less than 0.5 should not undergo bend type testing, as lower aspect ratios significantly increase the effects of shear and compression stress on the adhesive joint area.
Figure 2a – Bend type test Figure 2b – Shear type test
NOTE This figure illustrates two types of the test method for measuring adhesive strength between a columnar test piece and substrate
Configurations or specimen Supply and dimensions of specimen
1 Columnar test piece F loading force supplied by a kind of actuator
2 Substrate l p distance between the loading position and substrate
The knife edge of a loading tool is defined by the distance \( l \) from its tip to the substrate In bend type tests, the angle \( \theta_b \) is measured between the lateral face of a columnar test piece and the contact face of the knife edge Conversely, for shear type tests, the angle \( \theta_s \) represents the same relationship but focuses on shear forces.
Figure 2 – Adhesive strength test method
Data analysis
In adhesive strength test by bend loading, adhesive bend strength is calculated by the following Equation (1)
M a p c a p p σ = = = (1) where σ a is the adhesive bend strength;
Z is the section modulus of a columnar test piece;
M a is the bend moment at delamination;
F max is the maximum load at delamination; l p is the loading point from the root of a columnar test piece
In adhesive strength test by shear loading, adhesive shear strength is calculated by the following Equation (2)
F a p τ = = (2) where τ a is the adhesive bend strength;
A is the adhesive joint area between a columnar test piece and substrate;
F max is the maximum load at delamination
In the bend type test, it is crucial to be aware of the potential for exfoliation caused by shear force when the aspect ratio (l c /D) of the columnar test piece is below 1.2, as outlined in Section 4.1 and the relevant clause.
General
The test equipment must effectively apply microscopic displacements or micro-level forces to the test specimen It includes an actuator for displacement application, a sensor for measuring force, a controller that maintains a constant speed for displacement or force application, an alignment system to ensure proper positioning between the test piece and the loading tool, and a recorder to monitor the load during delamination.
Actuator
Displacement or force must be applied linearly along the loading axis of the test piece at a constant speed Therefore, the actuator must be capable of applying displacement or force linearly and consistently.
Force measurement sensor
For accurate measurement of adhesive strength, a load cell with sufficient resolution ensuring 5% accuracy must be utilized The force sensor should be oriented to measure the force in the loading direction, and the knife edge of the loading tool must be positioned within the effective measuring area of the force sensor, as illustrated in Figure 3.
Alignment system
The alignment system shall be capable of aligning the test piece and loading tool in the proper position to apply displacement or force in the correct direction (see 7.3).
Recorder
The test equipment shall include a recorder for detecting the force at delamination
Design of test pieces
The test piece must meet two key criteria: a) its dimensions, including columnar diameter and length, should align with the size of the device parts being evaluated; b) the gap (S) between test pieces must exceed twice the diameter (D) and length (l_c) of the columnar test piece to prevent interference with adjacent tests Additionally, the gap (S) should be significantly larger than the width of the knife edge tip of the loading tool (l_k) to ensure that only one columnar test piece is loaded at a time.
Preparation of test pieces
A number of columnar test pieces with the same manufacturing process and conditions are obtained, since a plurality of columnar test pieces are prepared on the same substrate
Test pieces must meet two key criteria: first, they should be prepared on a substrate using a manufacturing process and conditions that closely match those used for the thin film of the device being evaluated Second, a minimum of ten columnar test pieces must be produced simultaneously on the same substrate Adhesive testing should then be conducted on these test pieces under uniform testing conditions.
Method for gripping
The substrate of test pieces must be securely fixed to the testing device to prevent movement during the adhesive strength test, in accordance with clauses A.2 and A.3 of IEC 62047-2:2006 Additionally, the substrate should be positioned so that the loading direction of the test device is parallel to the substrate surface, as specified in section 7.3.
Speed of testing
Displacement speed, or loading speed, must remain constant during testing The appropriate speed is influenced by the testing environment, the type of testing machine used, and the stiffness of the test piece It is essential to select a speed that is optimal for the specific combination of environment, material, test piece, and testing machine Generally, the testing speed should be carefully chosen based on the intended application of the materials.
Alignment of test piece
The test piece must be aligned so that the substrate surface is parallel to the loading direction axis with an accuracy of 3° Refer to Figure 3 a) for visual guidance.
The alignment of loading equipment and substrate must adhere to specific criteria: the contact surface of the loading knife edge should be perpendicular to the plane that includes the loading axis and the normal of the test piece substrate For bend type tests, the distance between the loading tool and the substrate, denoted as \( l_t \), must exceed 10% of the columnar length \( l_c \) to prevent contact In shear type tests, the tip of the loading tool should maintain a specified distance \( l_t \) from the substrate to avoid any contact.
10 % of the columnar diameter (D), provided that D is 10 àm and larger l t should be within 1 àm, provided that D is less than10 àm See Figure 2 b)
Figure 3a – Side view of columnar test piece and loading tool Figure 3b – Cross-section of A-A ’
Configurations or specimen Direction or plane for alignment
1 Columnar test piece 5 Loading axis (loading direction)
2 Test piece substrate 6 Surface of test piece substrate
3 Loading tool 7 Contact surface of the loading knife edge
4 Load cell 8 Plane including loading axis and normal of a test piece substrate l k width of the knife edge tip
Figure 3 – Alignment between columnar test piece and loading tool
Test environment
As the environment greatly affects the adhesive properties of micro-materials, the test temperature and humidity should be controlled within ± 1 °C and ± 5 %, respectively
Test reports must include essential information such as a reference to IEC 62047-13, details about the materials used for the columnar test piece and substrate, their dimensions, and the spacing between adjacent test pieces Additionally, the reports should outline the preparation method for the test pieces, specify the test conditions including the test device and loading conditions, describe the test environment with temperature and humidity, and present the measurement results along with the calculated adhesive strength.
A.1 Outline of round-robin tests performed in Germany and Japan
The validity of adhesive strength test methods between a micro-sized columnar test piece and a substrate, as outlined in Clause 4, is confirmed through round-robin tests (RRT) detailed in this standard.
Round-robin tests (RRT) were performed from 2008 to 2009 in Germany and Japan The RRT were carried out with the participation of several universities in Germany and Japan
The RRT utilized epoxy-type photoresist, SU-8, and silicon wafers, with various dimensions of SU-8 columnar test pieces prepared for testing Micro-sized columnar test pieces of each dimension were fabricated on each wafer under consistent manufacturing conditions The RRT was conducted using specialized material testing machines for micro-sized materials at each institute, capable of applying precise displacement and/or force at a constant rate Adhesive tests were performed in displacement control mode, measuring both force and displacement throughout the testing process.
The adhesive strengths were compared within each of the different-sized columnar test pieces
On the basis of finding from the RRT, this standard was developed
Figure A.1 shows an example of the testing results obtained from the RRT in each institute
Specimen A diameter of 125 àm aspect ratio of 0,8
Specimen B diameter of 125 àm aspect ratio of 1,2 θ b Univ 1: 45°
Univ 1 Univ 2 Univ 3 Univ 1 Univ 2 Univ 3
M ax im um ten si le st res s at del am inat ion/ M P a
This graph illustrates the results of RRT obtained from bend type tests conducted on two different-sized SU-8 columns on a silicon substrate To account for the variability in adhesive strength data, 10 to 20 test pieces of each column size were evaluated at each institute.
NOTE 2 In columnar test pieces with an aspect ratio of 1,2 (specimen B), the maximum tensile stress at delamination (the adhesive bend strength) is about the same in each laboratory
In columnar test pieces with an aspect ratio of 0.8 (specimen A), the adhesive bend strength is comparable to that of specimen B at a knife edge angle of 10° However, at a knife edge angle of 45°, the adhesive bend strength in specimen A exceeds that of specimen B.
Figure A.1 – Example of the RRT results (see [1] 1 ) _
1 Figures in square brackets refer to the bibliography
A.2 Effects of the aspect ratio of columnar test piece on the adhesive bend strength in bend type test
This standard employs a columnar shape as the adhesive test specimen to assess the adhesive strength between micro-sized components and a substrate in MEMS The columnar design allows for point loading at the end, facilitating adhesive tests under bend loading conditions This approach enables effective loading at the specimen's end without requiring precise alignment adjustments.
The aspect ratio of columnar specimens significantly influences the adhesive strength observed during adhesive testing under bending loads As illustrated in Figure A.2, a decrease in the aspect ratio leads to an increase in the ratio of shear stress to maximum tensile stress.
For columnar test pieces with an aspect ratio of less than 0.5, there is a significant risk of delamination due to increased shear stress, as illustrated in Figure A.2 Therefore, it is essential to utilize a shear loading type for these columnar test pieces.
In columnar tests with an aspect ratio ranging from 0.5 to 1.2, the effective stress responsible for delamination shifts from shear stress to maximum tensile stress as the aspect ratio increases, as illustrated in Figure A.2 This raises uncertainty regarding the primary cause of delamination—whether it is due to shear stress, maximum tensile stress, or a combination of both Consequently, it is advisable to avoid using bend type tests on columnar specimens with an aspect ratio of 0.5 to 1.2.
Aspect ratio (columnar length / diameter)
Shear stress / Max tensile stress
Aspect ratio (columnar length/diameter)
S hear s tres s/ m ax im um te ns ile st re ss
Figure A.2 – Effects of aspect ratio of columnar test piece on the stress condition in bend type test (see [2])
A.3 Effects of knife edge angle of loading tool on the adhesive bend strength in bend type test
In bend type tests, increasing the knife edge angle of the loading tool (θ b) raises the ratio of compression stress at the adhesive joint area to the maximum tensile stress at the columnar root This effect becomes significant at larger angles, as illustrated in Figure A.3 Therefore, it is recommended that θ b be maintained between 10° and 20° during bend type testing.
Aspect ratio (Columnar length / diameter )
C om pr es si on s tres s / M ax t ens ile s tres s
Aspect ration (columnar length/diameter)
C om pr es si on s tres s/ m ax imu m ten si le s tres s
NOTE Each line in this graph shows the calculated result using each different knife edge angle of loading tool to the lateral face of columnar test piece
Figure A.3 – Effects of knife edge angle of loading tool and aspect ratio of columnar test piece on the stress condition in bend test
[1] Toshikazu Tasaki, Tso-Fu Mark Chang, Chiemi Ishiyama, Masato Sone, Study on delamination mechanism of SU-8 micropillars on a Si-substrate under bend loading by
[2] Chiemi Ishiyama, Akinobu Shibata, Masato Sone, and Yakichi Higo Effects of Aspect
Ratio of Photoresist Patterns on Adhesive Strength between Microsized SU-8 Columns and Silicon Substrate under Bend Loading Condition Japanese Journal of Applied
5.3 Capteur de mesure de la force 22
Figure 1 – Éprouvettes d'essai en colonnes 20
Figure 2 – Méthode de l'essai de la résistance d'adhérence 21
Figure 3 – Alignement d'une éprouvette d'essai en colonnes et d'un outil de charge 24
Figure A.1 – Exemple de résultats des RRT (voir Bibliographie [1]) 27
Figure A.2 – Effet du rapport de forme de l'éprouvette d'essai en colonnes sur la contrainte de traction dans des conditions d'effort de courbure (see Bibliography [2]) 28
Figure A.3 illustrates the impact of the knife blade angle, the loading tool, and the specimen's aspect ratio on the stress condition during curvature testing.
Partie 13: Méthodes d'essais de types courbure et cisaillement de mesure de la résistance d'adhérence pour les structures MEMS
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Généralités
The current standard outlines the testing methods for adhesion between a column test specimen and the substrate A constant speed is used to apply displacement or force to the column test specimen, measuring the force during interlaminar separation to evaluate the adhesion strength A conical-tipped knife blade tool is employed to apply force to the column test specimen, with the blade angle adjusted according to different types of adhesion strength measurement loads.
In measuring the adhesion resistance to curvature by applying a bending force at the end of a column test specimen, the knife blade of the loading tool is positioned with its tip angled upward relative to the specimen, as shown in Figure 2 a) This orientation facilitates the alignment of the loading tool and the test specimen, as a concentrated load is applied at the end of the column specimen It is essential to ensure that the bending test does not result in pure bending, which would introduce a compressive component at the root of the column This compressive component increases with the angle of contact of the knife blade To minimize the effect of this compressive component, the contact angle of the knife blade (θ b) should be maintained between 10° and 20°.
In measuring the shear adhesion resistance by applying a shear force to the lateral face of a column test specimen, a line load is applied using a loading tool that is parallel to the cylinder's lateral face It is essential for the testing apparatus to include a precise alignment system to ensure the knife blade is aligned parallel to the cylinder's lateral face Alternatively, the knife blade can be inclined downward towards the test specimen to minimize curvature stress effects The angle error (\(\theta_s\)) should be maintained between 0° and 15° Test results from curvature tests are influenced by the aspect ratio (\(l_c/D\)), particularly when this ratio is below 1.2 Additionally, curvature tests should not be conducted on column test specimens with an aspect ratio below 0.5, as the effects of the aspect ratio on shear and compressive stress near the adhesive bond area significantly increase with a decreasing aspect ratio.
Figure 2a – Essai de type courbure Figure 2b – Essai de type cisaillement
NOTE Cette figure illustre les deux types de la méthode d'essai prévue pour mesurer la résistance d'adhérence entre une éprouvette d'essai en colonnes et le substrat
Configurations ou éprouvette Fourniture et dimensions de l'éprouvette
1 Éprouvette d’essai en colonnes F effort de charge fourni par un certain type d'actionneur
2 Substrat l p distance entre la position de la charge et le substrat
The article discusses three key angles related to knife blade tools in testing applications The first angle, denoted as \( l \), represents the distance between the tip of the loading tool and the substrate The second angle, \( \theta_b \), is the angle between the side face of a column test specimen and the contact face of the knife blade during bending tests Lastly, the angle \( \theta_s \) refers to the angle between the side face of the column test specimen and the contact face of the knife blade during shear tests.
Figure 2 – Méthode d'essai de la résistance d'adhérence
Analyse des données
Dans l'essai de résistance d'adhérence par effort de courbure, la résistance d'adhérence à la courbure est calculée par l'Équation suivante (1) max 3 3 max 32
M a p c a p p σ = = = (1) ó σ a est la résistance d'adhérence à la courbure;
Z est le module de section d’une éprouvette d'essai en colonnes;
M a est le moment de courbure lors du décollement interlaminaire;
F max est la charge maximale lors du décollement interlaminaire; l p est le point d'application de la charge depuis la racine d’une éprouvette d'essai en colonnes
Dans l'essai de résistance d'adhérence par effort de cisaillement, la résistance d'adhérence au cisaillement est calculée par l'Équation suivante (2) max 2 max 4
F A a F p τ = = (2) ó τ a est la résistance d'adhérence à la courbure;
A est la zone de liaison adhésive entre une éprouvette d'essai en colonnes et le substrat;
F max est la charge maximale lors du décollement interlaminaire
In a curvature effort test, it is essential to consider the possibility of exfoliation caused by shear force when the aspect ratio (l c /D) of the test specimen in columns is less than 1.2 Refer to section 4.1 and Article A.2 for further details.
Généralités
Testing equipment must be capable of applying microscopic displacement or micro-level force to the test specimen This equipment includes an actuator designed to apply displacement, a force measurement sensor, a regulator to maintain a constant application speed of displacement or force, an alignment system between the test specimen and the loading tool, and a recording device to detect the load during interlaminar delamination.
Actionneur
It is essential to apply displacement or force linearly along the load axis of the test specimen at a constant speed Therefore, the actuator must be capable of applying displacement or force linearly at a consistent rate.
Capteur de mesure de la force
A load cell with adequate resolution, ensuring a 5% accuracy of the measured adhesion resistance, is essential for force measurement The force sensor must be calibrated to measure force in the direction of the load Additionally, the knife blade of the loading tool should be positioned within the effective measurement surface of the force sensor.
Système d'alignement
Le système d'alignement doit permettre l'alignement entre l'éprouvette d'essai et l'outil de charge dans la position appropriée, en vue d'appliquer le déplacement ou la force dans l'axe approprié (voir 7.3).
Appareil enregistreur
L'équipement d'essai doit comprendre un appareil enregistreur, en vue de détecter la force lors du décollement interlaminaire
Conception des éprouvettes d’essai
The test specimen must meet two key criteria: a) the dimensions, including diameter and length, should be comparable to the size of the components being evaluated; b) the spacing (S) between test specimens should exceed twice the diameter (D) and the length (l_c) of the test specimen to prevent interference with adjacent specimens during testing Additionally, the spacing should be significantly greater than the width of the knife blade tip (l_k) of the loading tool to avoid subjecting two test specimens to stress simultaneously.
Préparation des éprouvettes d'essai
A number of test columns are produced under identical manufacturing processes and conditions, as multiple test columns are prepared on the same substrate.
Test specimens must meet two key criteria: a) They should be prepared on a substrate using a manufacturing process and conditions that closely resemble those used in the production of the thin film of the device being evaluated; b) A minimum of ten test specimens should be prepared simultaneously on the same substrate Additionally, adhesion testing should be conducted using more than ten test specimens under the same testing conditions (refer to Article A.1).
Méthode de préhension
The test specimen substrate must be securely fixed by adhering to two key points: a) it should be attached to the testing device in a manner that ensures its immobility during the adhesion strength test, in accordance with Articles A.2 and A.3 of IEC 62047-2:2006; b) the substrate must be oriented so that the load direction of the testing device is parallel to the surface of the substrate, as outlined in section 7.3.
Vitesse d’essai
It is essential to maintain a consistent speed of movement or load during testing Since the testing speed is influenced by the testing environment, the type of testing machine used, and the rigidity of the test specimen, it is crucial to select the most suitable speed for the specific combination of environment, material, specimen, and testing machine.
Généralement, il convient de choisir correctement la vitesse d'essai en fonction de l'application des matériaux.
Alignement de l’éprouvette d’essai
The alignment of the test specimen must meet the following requirement: a) The surface of the substrate of the test specimen must be parallel to the load direction axis within a precision of 3° Refer to Figure 3 a).
Additionally, it is essential that the alignment of the charging equipment and the substrate meets three key criteria: b) The contact surface of the charging knife blade must be perpendicular to the plane that includes the load axis and must also be perpendicular to the substrate of the test specimen.
In the case of curvature testing, the distance between the loading tool and the substrate, denoted as \( l_t \), should be greater than 10% of the column length \( l_c \) to prevent contact between the two For shear testing, it is essential to maintain the tip of the loading tool at a specific distance \( l_t \) from the substrate to avoid contact This distance \( l_t \) should be within 10% of the column diameter \( D \), provided that \( D \) is greater than or equal to 10 nm If \( D \) is less than 10 nm, \( l_t \) should be approximately 1 nm.
Figure 3a – Vue latérale d’une éprouvette d’essai en colonne et outil de charge Figure 3b – Section A-A’
Configurations ou éprouvette Sens ou plan de l'alignement
1 Éprouvette d’essai en colonnes 5 Axe de la charge (sens de la charge)
2 Substrat de l’éprouvette d’essai 6 Surface du substrat de l’éprouvette d’essai
3 Outil de charge 7 Surface de contact de la lame de couteau de charge
4 Cellule de charge 8 Plan incluant l'axe de charge et normal sur le substrat d'une éprouvette d'essai l k largeur de la pointe de la lame de couteau
Figure 3 – Alignement d'une éprouvette d'essai en colonnes et d'un outil de charge
Environnement d’essai
Comme l'environnement compromet grandement les propriétés d'adhérence des micromatériaux, il convient de réguler la température d'essai et l'humidité à ± 1 °C et ± 5 %, respectivement
Test reports must include at least the following information: a) reference to the current standard, namely IEC 62047-13; b) materials of the test specimen columns and substrate; c) dimensions of the test specimen columns and substrate, as well as the spacing between adjacent test specimens; d) method of preparation for the test specimen and relevant details; e) testing conditions related to the testing device and test load; f) testing environment such as temperature and humidity; g) measurement results and calculated adhesion strength.
A.1 Aperỗu des essais inter-laboratoires (RRT 1 ) pratiquộs en Allemagne et au
The validity of the adhesion strength testing methods between a microminiaturized column specimen and a substrate, as outlined in Article 4, is confirmed through inter-laboratory test results (RRT, round robin tests) described herein.
Les essais inter-laboratoires ont été réalisés de 2008 à 2009 en Allemagne et au Japon Les
RRT ont été effectués avec la participation de plusieurs universités d'Allemagne et du Japon
Les matériaux utilisés dans les RRT étaient une résine photosensible de type époxy, SU-8 et des tranches de silicium Plusieurs dimensions différentes d'éprouvettes d'essai en colonnes
SU-8 was designed for microfabrication testing A series of microminiaturized test specimens, each with specific dimensions, were produced under identical manufacturing conditions The tests were conducted using micro-scale material testing machines at various institutes, capable of applying precise displacement and/or force at a constant speed Adhesion tests were performed in displacement control mode, measuring both force and displacement during the experiments Adhesion strengths were compared across test specimens of different sizes This standard was developed based on the results of inter-laboratory tests.
La Figure A.1 montre un exemple de résultats d'essais obtenus par les RRT de chaque institut
Echantillon A diamốtere de 125 àm rapport de forme de 0,8
Echantillon B diamốtre of 125 àm rapport de forme de 1,2 θ b Univ 1: 45°
Univ 1 Univ 2 Univ 3 Univ 1 Univ 2 Univ 3
C ont rai nt e de t rac tion m ax im al e au déc ol lem en t i nt er lam inai re /M P a
This graph illustrates one of the results from the RRT, derived from curvature tests using two different sizes of SU-8 columns on a silicon substrate Approximately 10 to 20 test specimens of each column size were subjected to testing at each institute, as the adhesion strength data tends to be scattered.
In test tubes with a shape ratio of 1.2 (sample B), the maximum tensile stress at the interlaminar shear (adhesion strength at curvature) is consistently similar across all laboratories.
In test tubes with a shape ratio of 0.8 (sample A), the adhesion strength at curvature is approximately equal to that of sample B when the knife blade angle of the loading tool (θ_b) is 10° Conversely, the adhesion strength at curvature exceeds that of sample B when θ_b is 45°.
Figure A.1 – Exemple de résultats des RRT (voir [1] 2
A.2 Effets du rapport de forme de l'éprouvette d’essai en colonnes sur la résistance d'adhérence à la courbure dans un essai de type courbure
The current standard employs a columnar form for the adhesion test specimen to evaluate the adhesion strength between microminiaturized components and a substrate in MEMS This design is adopted because it allows for concentrated load application at the column's tip during adhesion tests under bending stress conditions Consequently, appropriate force can be applied at the end of the column specimen in a concentrated load mode, eliminating the need for precise alignment adjustments.
It is essential to consider the impact of the specimen's aspect ratio on the adhesion strength obtained from adhesion tests under bending conditions Figure A.2 illustrates that the ratio of shear stress to maximum tensile stress increases as the aspect ratio decreases.
In the case of a test specimen in columns with a slenderness ratio less than 0.5, there is a high likelihood of interlaminar delamination occurring due to shear stress, as the proportion of shear stress increases.
The numbers in brackets refer to the bibliography This is illustrated in Figure A.2 Therefore, for the column test specimen with the shape ratio, a shear-type effort must be adopted.
In column tests with a shape ratio between 0.5 and 1.2, the effective interlaminar shear stress is transferred to the maximum tensile stress as the shape ratio increases, as shown in Figure A.2 This indicates that identifying the cause of interlaminar delamination—whether due to shear stress, maximum tensile stress, or a combination of both—is challenging Therefore, it is advisable not to conduct adhesion tests with bending effort on test specimens in this specific shape ratio range.
Aspect ratio (columnar length / diameter)
Shear stress / Max tensile stress
Rapport de forme (longueur de colonne/diamètre)
C ont rai nt e de c is ai lle m ent / cont rai nt e de trac tion m ax im al e
Figure A.2 – Effet du rapport de forme de l'éprouvette d'essai en colonnes sur la contrainte de traction dans des conditions d'effort de courbure (voir Bibliographie [2])
A.3 Effets de l'angle de la lame du couteau de l'outil de charge sur la résistance d'adhérence à la courbure dans un essai de type courbure
In curvature testing, the ratio of compressive stress near the adhesive bond area to the maximum tensile stress at the root in columns increases as the angle of the knife blade of the loading tool rises.
(θ b ) Les effets ne peuvent pas être négligés à angle supérieur à θ b comme le montre la
Figure A.3 Ainsi, il convient d’avoir θ b compris entre 10 ° et 20 ° dans l'essai de type courbure
Aspect ratio (Columnar length / diameter )
C om pr es si on s tres s / M ax t ens ile s tres s
Rapport de forme (longueur de colonne/diamètre)
C ont rai nt e de c om pr es si on / cont rai nt e de trac tion m ax im al e
Each line of this graph represents the results calculated using a different knife blade angle applied to the side face of the test specimen in columns.
Figure A.3 illustrates the impact of the knife blade angle of the loading tool and the specimen shape ratio on the stress condition during curvature testing.
[1] Toshikazu Tasaki, Tso-Fu Mark Chang, Chiemi Ishiyama, Masato Sone, Study on delamination mechanism of SU-8 micropillars on a Si-substrate under bend loading by
[2] Chiemi Ishiyama, Akinobu Shibata, Masato Sone, and Yakichi Higo Effects of Aspect
Ratio of Photoresist Patterns on Adhesive Strength between Microsized SU-8 Columns and Silicon Substrate under Bend Loading Condition Japanese Journal of Applied