Thermal-mechanical strain characterization for printed wiring boards

Wu, T. Y.; Guo, Yifan; Chen, W. T.

doi:10.1147/rd.375.0621

Cited by 50 publications

(21 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, there exists a problem with PCB warpage in such device assembly during the solder reflow process. The excessive warpage of the PCB would result in some solder joint defects, such as short or open circuits, or thermal-mechanical strains in the PCB, seriously influencing the reliability of the PCB assembly [1]. The main factor causing the thermal-mechanical strains is a coefficient of thermal expansion (CTE) mismatch between the electronic components and the PCB, which would have a great deal of influence on the reliability of solder joints in microelectronic packages [2].…”

Section: Introductionmentioning

confidence: 99%

Measurements of Thermally-Induced Curvatures and Warpages of Printed Circuit Board during a Solder Reflow Process Using Strain Gauges

et al. 2017

View full text Add to dashboard Cite

Abstract:Measurements of the curvatures and warpages of a printed circuit board (PCB) during a thermal solder reflow process using strain gauges are proposed in this study. In the experiments, a shadow moiré is used for measuring the out-of-plane deformations (or warpage) of a bi-material plate and a PCB with dual in-line memory module (DIMM) sockets during solder reflow heating, while the finite element method (FEM) is used to analyze the thermally-induced deformation of the PCB specimen for ensuring the validity of the measurement. Conventional strain gauges are employed to measure the strains (albeit as in-plane strain data) in both specimens during the solder reflow process. The results indicate that the strain gauge-measured strain data from the top and bottom surfaces of both specimens during the solder reflow can be converted into curvature data with specific equations, and even into global out-of-plane deformations or warpages with a proposed simple beam model. Such results are also consistent with those from the shadow moiré and FEM. Therefore, it has been proved that the strain gauge measurement associated with the simple beam model can provide a method for the real-time monitoring of PCB deformations or warpages with different temperatures during the solder reflow process.

show abstract

Section: Introductionmentioning

confidence: 99%

Measurements of Thermally-Induced Curvatures and Warpages of Printed Circuit Board during a Solder Reflow Process Using Strain Gauges

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The material properties are assumed linear and isotropic, 8 well below the polymeric glass transition temperature ͑T g ͒ or below the silicon melting temperature ͑T m ͒. Flexibility coupling between the bonded polymer and silicon layers is considered in the constitutive equations,…”

mentioning

confidence: 99%

Powerful polymeric thermal microactuator with embedded silicon microstructure

Lau

Goosen

Keulen

et al. 2007

Applied Physics Letters

View full text Add to dashboard Cite

A powerful and effective design of a polymeric thermal microactuator is presented. The design has SU-8 epoxy layers filled and bonded in a meandering silicon ͑Si͒ microstructure. The silicon microstructure reinforces the SU-8 layers by lateral restraint. It also improves the transverse thermal expansion coefficient and heat transfer for the bonded SU-8 layers. A theoretical model shows that the proposed SU-8/Si composite can deliver an actuation stress of 1.30 MPa/ K, which is approximately 2.7 times higher than the unconstrained SU-8 layer, while delivering an approximately equal thermal strain. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2742599͔ Thermal actuators feature relatively high actuation stress or strain. However, they have shortcomings in terms of high power consumption and high operating temperatures. 1,2 To a large extent, their performance depends on the selected thermal expansion materials. 3 For example, silicon and metals with high moduli of elasticity produce high actuation stresses, but polymers with high thermal expansion coefficients ͑CTEs͒ deliver relatively high actuation strains. According to Ashby, 4 the linear CTE ͑␣͒ is almost inversely proportional to Young's modulus ͑E͒. This means that compliant but high-CTE polymers may not be ideal for generating large actuation stress and strain simultaneously. Owing to their electrical and thermal insulating properties, most polymers require integrated heaters to enable electrical activation. 2,5 The heaters are normally made of surface metallic films and may induce nonuniform heating across the polymeric thickness. This may inevitably cause out-of-plane bending to the polymeric layers.In this letter, we present a design of polymeric thermal actuators to accomplish enhanced in-plane actuation. This design combines multiple materials for effective thermal actuation. It consists of an aluminum film heater, a silicon ͑Si͒ microstructure, and polymeric epoxy ͑SU-8͒ encapsulant ͑see Fig. 1͒. The silicon microstructure is meandering in shape and has a high aspect ratio. Its gaps and surrounding areas are filled and encapsulated with SU-8 epoxy, whereas its top is covered with the aluminum ͑Al͒ heater. The Si "skeleton" serves to conduct heat and to reinforce the SU-8 encapsulant; the Al line is responsible for resistive heating; whereas, the SU-8 epoxy serves to expand and open the spacing of the Si skeleton.The proposed design has been fabricated using bulk micromachining of silicon and casting of SU-8-2002 polymer. 6 Testing shows that a 530-m-long sample device ͑consisting of a 0.675-m-thick Al film and a 50-m-high Si microstrcutrure͒ delivers a 2.5% in-plane longitudinal strain at 2 V, while consuming less than 27 mW ͓see Fig. 1͑b͔͒, and shows no noticeable out-of-plane motion. The actuation using this composite design is efficient. This motivates investigation into its potential actuation capabilities. The normal activation of the actuator design by resistive heating causes an unknown and nonuniform temperature distribution. This ma...

show abstract

“…Thus, the deformation incurred by the temperature increment is locked into the grating and recorded at room temperature. Numerous examples can be found in the literature [20,21,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41].…”

Section: Microelectronics Devicementioning

confidence: 99%

Recent Applications of Moiré Interferometry

Ifju

Han

2010

Exp Mech

View full text Add to dashboard Cite

Moiré interferometry has been a valuable experimental technique for the understanding of the mechanical behavior of materials and structures. Over the last decade less emphasis has been placed on the development of the technique and more towards applications. This paper is a review article on recent applications using moiré interferometry in the fields of microelectronics devices, material characterization, micromechanics, residual stress, composite materials, fracture mechanics, and biomechanics. The general principles of moiré interferometry and advancement of techniques will not be discussed in this text, but references will be provided.

show abstract

Thermal-mechanical strain characterization for printed wiring boards

Cited by 50 publications

References 8 publications

Measurements of Thermally-Induced Curvatures and Warpages of Printed Circuit Board during a Solder Reflow Process Using Strain Gauges

Measurements of Thermally-Induced Curvatures and Warpages of Printed Circuit Board during a Solder Reflow Process Using Strain Gauges

Powerful polymeric thermal microactuator with embedded silicon microstructure

Recent Applications of Moiré Interferometry

Contact Info

Product

Resources

About