10 20 30 40 50 200
250 300 350 400 450
Weibull modulus, m
Influence of metallisation on the mechanical behaviour of Low Temperature Co-fired Ceramics under biaxial loading
R. Bermejo¹ ,a , L. Sestakova 2 , I. Kraleva², P. Supancic 1,2 , R. Danzer 1,2
1 Institut für Struktur- und Funktionskeramik (ISFK), Montanuniversität Leoben, Austria
2 Materials Center Leoben Forschung GmbH, Leoben, Austria
a
Corresponding author‘s e-mail address: raul.bermejo@unileoben.ac.at
Acknowledgements
Financial support by the Austrian Federal Government (in particular from the Bundesministerium für Verkehr, Innovation und Technologie and the Bundesministerium für Wirtschaft und Arbeit) and the Styrian Provincial Government, represented by Österreichische Forschungsförderungsgesellschaft mbH and by Steirische Wirtschaftsförderungsgesellschaft mbH, within the research activities of the K2 Competence Centre on “Integrated Research in Materials, Processing and Product Engineering”, operated by the Materials Center Leoben Forschung GmbH in the framework of the Austrian COMET Competence Centre Programme, is gratefully acknowledged. The company EPCOS OHG, Deutschlandsberg, Austria, is also acknowledged for providing the material for this investigation.
Introduction
Experiments
Mechanical strength results
The aim of this work is to study the mechanical strength of LTCCs under biaxial loading and investigate the effect of metallisation on the propagation of cracks.
The mechanical strength is determined in
≈10×10×0.4 mm 3 plates using the B3B test.
Motivation
The failure stress (equiv. tensile stress) is calculated with FEA:
( )
[
0]
2max
eq,
2 . 58 0 . 67 / 1
t t P t − ⋅
⋅
− σ =
P = Failure load (N), t = thickness (mm), t
0= 0.43 mm
Summary
Low Temperature Co-fired Ceramics (LTCCs) are 3D micro-network of metal structures embedded within a glass-ceramic substrate. They are used as high precision electronic devices (e.g. mobile and automotive technologies).
The different internal architectures can influence the strength reliability of the LTCC and its expected lifetime.
+ The mechanical strength of LTCC components depends on whether their upper or lower side is put under tension.
+ There is also an influence of the surface feature (i.e. metal pad, electrode, via) on the biaxial strength distribution.
+ The internal architecture of the component has an effect on the crack path, influencing the strength reliability.
Testing conditions: 0.5 mm/min, 40% RH and 25°C.
Fracture features of tested LTCCs with the upper side under tension
The strength of both a) the upper side and b) the lower side of the LTCCs is evaluated.
0 σmax
a) b)
Maximal stress distribution around location 2.
1 2
3 4
1 2
3 4
Weibull diagram of LTCC components und bulk material tested under biaxial flexure.
The characteristic strength, σ
0(F=63.21%) is also plotted versus the Weibull modulus, m.
Series-1
Series-3
Series-3
Series-4
Different locations (e.g. vias, metal-pads) are tested and compared to bulk LTCC.
100 μm
Metal-Via Metal-Electrode
Ceramic layer
Cross-section of a typical LTCC component
Fracture features of tested LTCCs with the lower side under tension
1 3
Fracture origin marked with yellow circle.
10 15 20 25 30 35
0.67 1.81 4.86 12.66 30.78 63.21 93.40
99.94 154 308 462
-5 -4 -3 -2 -1 0 1 2 Equiv. failure stress,
σeq, max[MPa]
Bulk Series-1 Series-2 Series-3 Series-4
Ln L n 1/( 1 - F )
P ro bab ili ty of f a ilure , F [%]
Failure load, P [N] 10 15 20 25 30 35
0.67 1.81 4.86 12.66 30.78 63.21 93.40
99.94 154 308 462
-5 -4 -3 -2 -1 0 1 2 Equiv. failure stress,
σeq, max[MPa]
Bulk Series-1 Series-2 Series-3 Series-4
