Note Key Statements of our papers published in DVS Reports Vol. 375
"New technological approach for soldering technology based on the argumentation of thermodynamic impacts in soldering processes"
as well as deductive evidence to be considered.
Presupposition
The repeatability of soldering defects is shown to be too high to be cogently assossiated with State-of-the-Art troubleshooting.
Statement 1/2 (Empirical Basis)
Specific soldering defects are assigned to specific designs. The strength of the heat loss and the number of solidification fronts that occur can be determined from the design.
Statement 2/2 (Thermal conductivity
λ)
Considering the coefficient of thermal conductivity λ (Cu:370W/mK, FR4:0,2 W/mK) the striking factor of 1850 implicates a directed heat dissipation via Cu.
Divergences
Depending on Layout and Design and in accordance with the consideration of directed heat dissipation, various types of Divergences occur within the solder structure in the course of soldering processes.
With "local-abrupt"(wave- & selective soldering) and "global-successive"(reflow) two basic types of heating termination are identified additinally affecting the development of divergences.
Operative Divergency Clearance (ODC)
With the technological approach ODC, manageable adjustments made in process engineering prevent the occurence of divergences within the solder structure.
It now is the objective to create a successive one-front-contraction of the solder, which can also be described as a convergent cooling of the structure,
Depending on the heat dissipation behavior the following types of divergence are identified as the cause for several soldering defect.
Linear Divergence / successive two-front-contraction
Opposite course of two solidification fronts with shrinkage direction opposite to the direction of progression.
Volume loss: linearly distributed
Potentiated Divergence / successive multi-front contraction
Opposite course of multiple solidification fronts with shrinkage direction opposite to the direction of progression.
Volume loss: point-like concentrated
Diffuse Divergence / none-front-contraction, abrupt/successive
Opposite course of non-substantial solidification fronts with shrinkage direction opposite to the direction of progression.
Volume loss: diffuse distributed
Spherical Divergence / max-front-contraction,nearly abrupt
Opposite course of maximum directional solidification fronts with shrinkage direction opposite to the direction of progression.
Volume loss: spherical concentrated
The working principle of the technological approach presented, creating a high degree of regularity within the structure, utilizing the dominance of a directed heat source or heat outlet constantly.
Aspects from the system explored here to be relevant also for other fields of research and technology:
Convergence-Pad
Soldering Solution
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