Solar Cell Solder Pad Dressing via CNC Vacuum Nozzle
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Solution Overview
Problem
Solar cell modules suffer from solder voids that reduce contact area and increase junction temperature, leading to efficiency drops and potential failure, especially in concentrated photovoltaic systems, and existing reworking methods are not precise enough to address these issues effectively.
Innovation Solution
A vacuum reflow voiding system that uses a sealed chamber with heat and vacuum to collapse solder voids, combined with precision control of heating elements and a CNC machine to accurately remove excess solder, effectively reducing voids and improving thermal transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hand-held tools are used to dress solder pads, then the equipment is simple and easy to operate, but the precision is insufficient to avoid damaging surrounding components, traces, and solder pads
Solution Approach 1:
The patent replaces manual mechanical hand-held tools with an automated system that uses a controllable heat source (such as a laser or focused heating element) guided by a controller to precisely remove excess solder. This substitution of mechanical manual operation with a controlled thermal field enables precision dressing while reducing the complexity of manual skill requirements.
Solution Approach 2:
The patent introduces a controller as an intermediary between the operator and the heat source, and uses a vacuum chamber as an intermediary environment to contain the solder removal process. The controller precisely regulates the heat source positioning and temperature, while the vacuum chamber prevents solder from spreading to surrounding areas, together enabling precise solder pad dressing.
2Reliability
If excess solder is removed using imprecise methods, then the process is simple, but surrounding components, traces, and solder pads are damaged
Solution Approach 1:
The patent applies heat locally and precisely to the specific area of excess solder that needs removal, rather than heating a broad area. The controllable heat source can be positioned and focused on the exact location requiring solder removal, allowing selective removal without affecting surrounding components, traces, or pads.
Solution Approach 2:
The patent uses a vacuum chamber as an inert environment to contain the solder removal process. The vacuum prevents atmospheric contamination and controls the behavior of molten solder, preventing it from spreading to surrounding areas. This controlled environment protects surrounding components while enabling effective solder removal.
3Manufacturing precision
If solder voids are present in the solder joint, then the manufacturing process is simple, but the contact area is reduced and junction temperature increases
Solution Approach 1:
The patent utilizes phase transitions of solder (solid to liquid to vapor) to remove voids. The controllable heat source heats the solder joint to melt the solder and expand voids, then the vacuum chamber evacuates the vapor and collapsed voids. This controlled phase transition process eliminates voids while maintaining sound solder joints.
Solution Approach 2:
The patent combines the heating and vacuum evacuation processes in a continuous sequence within the vacuum chamber. The heat source continuously melts and redistributes solder while the vacuum continuously evacuates voids and vapor, maintaining a continuous useful action that progressively eliminates voids throughout the solder joint.
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 method significantly reduces solder voids, enhancing thermal and electrical contact, thereby improving the efficiency and reliability of solar cell modules by maintaining lower junction temperatures and preventing module failure.
Implementation Method 1
applying a vacuum to a sealed chamber... The vacuum pulls out air in the void, termed degassing, thereby collapsing the void by raffling the solder into the void area
Implementation Method 2
heating to a melting point the solder... heating the solder comprises heating an area of the solder that substantially encompasses a void in the solder
Implementation Method 3
heating a vacuum nozzle having a tip to a first temperature that is equal to or greater than a melting temperature of the solder
Implementation Method 4
applying a vacuum to the vacuum nozzle... scanning a first area on the substrate... removing excess solder
Data Source
AI summary
A process for dressing a solder pad removes excess solder from locations that should be free of solder, such as circuit traces, other solder pads, and components near the solder pad being dressed. A first area of a substrate comprises solder to be removed and is heated to a first temperature. A second area of the substrate is heated to a second temperature. A vacuum nozzle is heated to a third temperature sufficient to melt the solder and is scanned across the area to be dressed, melting and vacuuming away the excess solder. The scanning process is controlled using a computer numerical controlled (CNC) machine.