Experimental study on the effect of reflow soldering temperature profile on the solder joint shape

Not only the stand-off height but also the shape of a solder joint has a strong influence on the joint reliability under temperature cycling. The shape determines the size of the local stress and strain concentrations. It is therefore very important to know well the joint shape after reflow. In a previous paper closed analytical expressions were derived for liquid bump shapes, as a function of pad size and bump height [1]. The bump deformation as a function of the chip weight could be derived from the force constant. In the present paper closed analytical expressions are derived for the force constant for liquid bumps having unequal spherical pad sizes. It turns out that the force constant for compression can be optimized as a function of the ratio of those pad sizes. The shape of the bump and especially the contact angle is of interest for modeling activities where geometrical effects do play a role. Furthermore from the variation in bumps heights on a chip an estimate can be made of the tilt of the chip after assembly. The solder profile estimation by the analytical expressions is validated by experimental results. Also a comparison with the solder profile estimation by the simulation software Surface Evolver is done. Both comparisons showed that the analytical estimation of the standoff height is very good as long as the gravitation energy contributed by the chip weight is less than 10% of the total energy. Finally, an example is shown where the analytical model and Surface Evolver are the geometrical input for a finite element model. The example considers a CSP assembled at both sides of the printed circuit board.

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An Experimental Study of the Mixing by an Acoustically Pulsed Axisymmetrical Air-Jet

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/85-gt-49 ◽

1985 ◽

Cited By ~ 1

Author(s):

P. J. Vermeulen ◽

Wai Keung Yu

Keyword(s):

Experimental Study ◽

Temperature Profile ◽

Strouhal Number ◽

Jet Flow ◽

Velocity Pulsation ◽

Entrainment Rate ◽

Air Jet ◽

Toroidal Vortices

The mixing by an acoustically pulsed axisymmetrical air-jet, flowing into the atmosphere, has been studied by means of velocity and temperature profile measurements. The strength of the velocity pulsation imparted to the jet flow and of the associated toroidal vortices were also measured. The entrainment rate was increased by up to two times, with the majority of the extra entrainment occurring over the first five diameters downstream of the jet orifice, where toroidal vortices are formed and attain their greatest strength. The jet response depends on Strouhal number and appears to be optimum at about 0.25. The response starts to saturate at the limit of pulsation strength used.

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Reflow Process Simulation for Dispersion Evaluation of Solder Joint Shape on Chip Component

ASME 2009 InterPACK Conference, Volume 2 ◽

10.1115/interpack2009-89019 ◽

2009 ◽

Cited By ~ 1

Author(s):

Kanji Takagi ◽

Qiang Yu ◽

Tadahiro Shibutani ◽

Hiroki Miyauchi

Keyword(s):

Surface Tension ◽

Solder Joint ◽

High Reliability ◽

Electronic Components ◽

Reflow Process ◽

Solder Joint Reliability ◽

Automotive Electronic ◽

Joint Reliability ◽

On Chip ◽

Joint Shape

The miniaturization and high reliability for automotive electronic components has been strongly requested. Generally, electronic component and printed wiring board are connected using solder joint. The reliability of solder joint has widely dispersion. For the dispersion reduction of solder joint reliability, not only design factors but manufacturing factors should be optimized. The evaluation of manufacturing factors for solder joint reliability was very difficult by experimental evaluation alone. Therefore, the reflow process simulation was established. The simulation was reenacted soldering process on chip component, which was the most severe reliability in automotive electronic components. The novelty of simulation was the coupled analysis of flow and rigid for simulating self-alignment of chip component. In this simulation, contact angle and surface tension was very important factor. So, these characteristics were measured based on Spread test and Wetting balance tests using the specimens. In the result, the solder joint shape of analysis was agree with the one of specimens using the measured contact angle and surface tension. Next, the effect of manufacturing process dispersion for solder joint shape was evaluated. The factors were mount offset and length unbalance of electrodes on chip component. As a result, the mount offset was not affected solder joint shape of chip component until a certain level. Also, the unbalance of electrode of chip component was not almost affected for solder joint shape of chip component because a part was moved to the center of part by surface tension of solder joint. Finally, the relation between the estimated solder joint shape and fatigue life of solder joints is evaluated using crack propagation analysis based on Manson-Coffin’s law and Miner’s rule. When the value of mount offset was large, the crack propagation mode was changed and the fatigue life of solder joint was decreased. As mentioned above, it was able to evaluate the relation between manufacturing factors and solder joint reliability. Accordingly, this simulation was very useful for consideration on the miniaturization, high reliability and appropriate margin for design of electronic components.

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