Ultrasonic-Assisted Solder Transfer for Semiconductor Substrates
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Solution Overview
Problem
Existing methods for transferring solder contacts onto semiconductor substrates, such as Injection Molded Soldering techniques, involve thermal cycling that causes stress and potential damage to the substrates, leading to performance issues and reduced yields due to temperature-induced changes and material migration.
Innovation Solution
The use of an ultrasonic-assisted solder transfer method where an ultrasonic head applies high-frequency vibrations in a longitudinal direction to melt and attach solder to substrate locations, minimizing thermal cycling and physical stress by using a decal with through-holes filled with solder, which can be aligned with substrate pads, and optionally combined with controlled external heating to manage substrate temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal compression is used to reflow solder, then solder attachment is achieved, but substrate stress and internal damage increase
Solution Approach 1:
The patent applies ultrasonic vibration to the solder material to induce melting and reflow without significantly heating the substrate. The ultrasonic energy directly agitates the solder atoms, causing frictional heating localized to the solder material itself, thereby achieving solder attachment while minimizing thermal stress on the substrate.
Solution Approach 2:
The patent replaces the traditional thermal field (heating system) with an ultrasonic field (mechanical vibration system) to achieve solder reflow. This substitution eliminates the need for broad thermal cycling that causes substrate stress, while still achieving the desired solder melting and attachment through localized ultrasonic energy input.
2Quantity of substance
If temperature cycling is increased to reflow solder, then solder reflow is achieved, but material migration and component deterioration increase
Solution Approach 1:
Ultrasonic vibration is applied directly to the solder material to induce rapid localized heating through internal friction and atomic agitation. This mechanical vibration method achieves complete solder reflow and melting while confining thermal effects to the solder material itself, preventing material migration and component deterioration that occur with conventional thermal cycling.
Solution Approach 2:
The patent changes the physical state and processing parameters of the solder material by applying ultrasonic vibration at specific frequencies and amplitudes. This causes the solder to transition from solid to liquid state through ultrasonic cavitation and frictional heating, achieving reflow without the need for elevated ambient temperatures that cause material migration.
3Temperature
If conventional heating methods are used, then solder melting is achieved, but process time and energy consumption increase
Solution Approach 1:
Ultrasonic vibration is applied to the solder material to induce rapid localized heating through internal friction and atomic agitation. This mechanical vibration method achieves complete solder reflow and melting while confining thermal effects to the solder material itself, preventing material migration and component deterioration that occur with conventional thermal cycling.
Solution Approach 2:
The patent employs periodic ultrasonic vibrations at high frequency to continuously agitate and heat the solder material. This periodic mechanical action efficiently transfers energy to the solder, causing rapid melting and reflow in a matter of seconds, significantly reducing the process time compared to conventional continuous heating methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces substrate stress and deterioration by allowing solder to reflow and attach within seconds without external heating, maintaining substrate integrity and improving yield by minimizing thermal cycling and chemical changes.
Implementation Method 1
An ultrasonic head applies high-frequency vibrations in a longitudinal direction to melt and attach solder to substrate locations
Implementation Method 2
allowing solder to reflow and attach within seconds without external heating
Data Source
AI summary
Apparatus and methods are disclosed for transferring solder to a substrate. A substrate belt moves one or more substrates in a belt direction. A decal has one or more through holes in a hole pattern that hold solder. Each of the solder holes can align with respective locations on one of the substrates. An ultrasonic head produces an ultrasonic vibration in the solder in a longitudinal direction perpendicular to the belt direction. The ultrasonic head and substrate can be moved together in the longitudinal direction to maintain the ultrasonic head in contact with the solder while the ultrasonic head applies the ultrasonic vibration. Various methods are disclosed including methods of transferring the solder with or without external heating.