Vacuum Reflow Solder Void Reduction in Solar Modules
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Solution Overview
Problem
Voids in the solder between solar cell dies and substrates in photovoltaic modules reduce the contact area and thermal heat transfer, leading to increased junction temperatures and potential module failure, especially in concentrated photovoltaic systems.
Innovation Solution
A vacuum reflow process is used to collapse solder voids by heating the solder to its melting point within a sealed chamber under vacuum, allowing air to escape and redistributing the solder to fill voids, which can be applied to various electronic and non-electronic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If soldering is performed to join solar cell die to substrate, then electrical connection is established, but solder voids are formed that reduce contact area and thermal heat transfer
Solution Approach 1:
The patent applies vacuum pressure before and during the soldering process to prevent air entrapment in the solder joint. By creating a vacuum environment prior to solder application and maintaining it during reflow, the system prevents void formation at the source, ensuring both electrical connectivity and thermal transfer without the need for post-soldering void removal.
Solution Approach 2:
The patent creates a vacuum environment (inert atmosphere without air or gases) during the soldering process. This inert environment prevents air from being trapped in the solder joint, eliminating the cause of void formation while maintaining both electrical and thermal performance of the solder connection.
2Ease of manufacture
If solder voids are present, then soldering process is simplified, but contact area is reduced increasing current density
Solution Approach 1:
The vacuum is applied before solder application and maintained throughout the reflow process. This preliminary and continuous vacuum application ensures that no air pockets are trapped during solder placement and melting, achieving complete wetting and maximum contact area without complicating the manufacturing process.
3Ease of manufacture
If solder voids are present, then soldering is easier, but thermal heat transfer area is reduced increasing junction temperature
Solution Approach 1:
By maintaining a vacuum environment throughout the soldering process, the patent eliminates air that would otherwise be trapped as voids in the solder joint. This ensures continuous thermal contact between the solar cell die, solder, and substrate, allowing efficient heat dissipation and keeping junction temperatures within acceptable limits.
4Reliability
If vacuum is applied to remove air from solder voids, then void area is reduced, but process complexity increases
Solution Approach 1:
The vacuum is applied before solder application and maintained continuously during the entire reflow process. This eliminates the need for separate post-soldering vacuum or hot air void removal steps, as voids are prevented from forming in the first place, thereby reducing overall process complexity while achieving excellent void reduction.
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 effectively reduces solder voids to less than 1% of the total solder area, enhancing thermal heat transfer and preventing module failure by ensuring a uniform solder thickness and increased contact area.
Implementation Method 1
applying a vacuum to a sealed chamber
Implementation Method 2
heating the solder to its melting point
Implementation Method 3
heating the solder to its melting point within a sealed chamber under vacuum, allowing air to escape and redistributing the solder to fill voids
Data Source
AI summary
A solar cell module comprises a solar cell soldered to a mounting element, such as a ceramic substrate. The solder bond can comprise a void. A method of reducing a solder void comprises reflowing the solder using a vacuum source and a heat source in a sealed chamber. The chamber is formed, at least in part, by a cowling into which the solar cell module is mounted. A system for reducing voids in a solder bond comprises a heat source and a vacuum source coupled to the sealed chamber into which a solar cell module is placed. The system can optionally include a control system that automates the execution of methods of reducing solder voids. The system can further include a pressure source to aid in reducing the solder void and reflowing the solder after the void is reduced.