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Journal of Materials Science

, Volume 30, Issue 21, pp 5543–5550 | Cite as

Characteristics of porosity in solder pastes during infrared reflow soldering

  • Y. C. Chan
  • D. J. Xie
  • J. K. L. Lai
Papers

Abstract

The effects of solder pastes and infrared reflow temperature profiles on the characteristics of porosity in solder joints are described. Porosity in solder joints can be detected by X-ray radiography. It was found that the composition and structure of solder pastes had the most significant effect on pore formation. However, a lower metal content and/or a higher heating rate did not necessarily cause a higher percentage of pores in solder joints. Results of experiments on pore formation processes during the whole infrared reflow soldering cycle show that high area fraction of pores in solder joints correspond to the peak temperatures in infrared reflow temperature profiles. To evaluate the thermal effect on the performance and structure of solder pastes, tests were also conducted using differential scanning calorimetry, thermogravimetric analysis (TGA) and weight loss in infrared reflow. It was found that the weight loss rate in the TGA curve and infrared reflow and floating speed of porosity are useful to predict the pore formation behaviour in the solder joint. It is recommended that an IR reflow process is chosen to fit with a suitable solder paste in order to decrease porosity in surface-mount solder joints.

Keywords

Porosity Differential Scanning Calorimetry Thermogravimetric Analysis Temperature Profile Solder Joint 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

A

Area sum of pores

Ai

Area of one pore

C

Constants

d, di

Diameter of a pore

di,max

Maximum axial dimension of a pore

di,min

Minimum axial dimension of a pore

g

Gravitation constant

Lj

Length of a copper land

M

Atomic weight of alloy

M1, M2

Atomic weight of pure metals

n

Number of molecules of gas

Pa

Atmospheric pressure

Pg

Internal gas pressure in a gas bubble

Ph

Hydrostatic pressure

Ps

Shrinkage pressure

R

Gas constant

r

Radius of a pore

Sj

Area of a copper land

S

Area sum of copper lands

T, Ti

Temperature

Tm

Melting point of alloy

V

Volume of a pore

Vm

Atomic volume at the melting point

Wj

Width of a copper land

w, wi

Weight loss of solder paste

x1, x2

Mole fraction in alloy

ɛ

Area fraction of pores

ɛv

Volume fraction of pores

β

Slope of TGA curve

ρ

Density of liquid alloy

ρm

Density of liquid alloy at the melting point

ρp

Tap density of solder paste

ρs

True density of solder metal

η

Viscosity of liquid solder metal

ν

Rising speed of a gas bubble

γ

Surface tension at the gas-metal interface

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References

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Copyright information

© Chapman & Hall 1995

Authors and Affiliations

  • Y. C. Chan
    • 1
  • D. J. Xie
    • 1
  • J. K. L. Lai
    • 1
    • 2
  1. 1.Department of Electronic EngineeringCity University of Hong KongKowloonHong Kong
  2. 2.Department of Physics and Materials ScienceCity University of Hong KongKowloonHong Kong

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