the effect of wire coating on the occurrence of fatigue failures during tmcl-testing by:arno vissers...
Post on 21-Dec-2015
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![Page 1: The effect of wire coating on the occurrence of fatigue failures during TMCL-testing By:Arno Vissers Jasper Winkes](https://reader036.vdocuments.mx/reader036/viewer/2022062407/56649d555503460f94a3255d/html5/thumbnails/1.jpg)
The effect of wire coating on the occurrence of fatigue failures during
TMCL-testing
By: Arno Vissers
Jasper Winkes
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Objective:
• Study the wire-shape.
• Development of parametric 2-D FEM model.
• Calculate the wire plastic strain with and without a coating.
• Calculate the total strain with and without a coating.
• Recommendations for the coating material
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Wire shape
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2-D FEM Model
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2-D FEM Model
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2-D FEM Model
• Variable geometry: - wire thickness;
- coating thickness.
• Mesh creation: af_planar_quad_trimesh *.
• Contact Body with contact type glue between materials.
• Initial conditions: Cooldown from 150 to –65 deg C.
• Material definitions: -Variable E-modulus of coating
• Generalized plain strain elements (Type 19)
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Results
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Results
Fig. 1 Total Strain (thick Wire)
Fig. 2 Total Strain (thin Wire)
Fig. 3 Plastic strain (Solder bump place)
Fig. 4 Plastic Strain (Lead place)
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Effect of coating on equivalent total strain on wire
No Coating:
Wirethickness 15 um ets 0.17
Wirethickness 30 um ets 0.15
Wirethickness 50 um ets 0.17
With coating
Same ets for all wirethickness, coatingthickness and coating elasticity modules
ets 0.02
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Effect of coating thickness on total equivalent plastic strain (teps) in the wire
Wirethickness 15 um (coating elasticity 5 MPa)– No coating teps 0.21
– CT 1 um teps 0.18
– CT 5 um teps 0.14
– CT 10 um teps 0.09
– Substantial reduction of plastic strain with increasing coating thickness
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Effect of coating elasticity on equivalent total strain on coating
Wirethickness 15 um (coating thickness 5 um)– 1 MPa ets 1
– 5 MPa ets 0.7
– 10 MPa ets 0.5
Thicker wire results in higher ets in the coating
Thinner coating results in higher ets in the coating
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Uncertainties
• Coarse mesh while simulating gives uncertain results.
• No solder bumps were modeled.
• Fracture analyses was not taken into account.
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Conclusions
• No plastic strain in coating since E-wire >> E-coating
• Use of coating leads to reduction of plastic strain in wire.
• Coating elasticity Total strain in coating • Thickness coating Total strain in coating • Wire thickness Influence of coating
thickness on plastic strain in wire
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Future perspectives
• With ever decreasing wire thickness (which leads to reduction of material costs) coating is a good way to prevent the occurrence of wire fractures.
• If the wires are isolated with a coating there is less chance of electronic short-circuit while injection molding the compound.