Segmented Solar Cell Busbar Structure for Cold Soldering
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Solution Overview
Problem
Solar cell designs with busbars often suffer from poor contact with solder strips, leading to cold soldering and power losses due to micro cracks and inefficient silver paste usage.
Innovation Solution
The electrode structure features busbars with sub-busbars and fingers, where the first sub-portions of the sub-busbars protrude to improve soldering tension and reduce micro cracks, and the ratio of distances between sub-portions is optimized (1.2≤l1/l2≤2) to enhance soldering and reduce silver paste waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrode pads are connected to busbars using ultra-thin solder strips, then the solar cell string can be formed, but poor contact occurs leading to cold soldering and power losses
Solution Approach 1:
The busbar is segmented into multiple sub-busbars (first sub-busbar, second sub-busbar, third sub-busbar, fourth sub-busbar) arranged in parallel. This segmentation increases the total contact area between the electrode pad and the busbar system, distributing the current flow across multiple contact points and reducing contact resistance, thereby improving soldering reliability and reducing power losses.
Solution Approach 2:
The invention transitions from a single-plane busbar contact to a multi-dimensional contact structure where sub-busbars are arranged both laterally (along the busbar length) and vertically (stacked in layers). This multi-dimensional arrangement maximizes the contact interface area between the electrode pad and busbar system, enhancing soldering tension and electrical contact quality.
2Reliability
If conventional busbar designs are used, then the structure is simple, but micro cracks form during assembly reducing reliability
Solution Approach 1:
The busbar is divided into multiple sub-busbars that can move independently. This segmentation allows each sub-busbar to accommodate thermal expansion and mechanical stress separately, preventing crack propagation across the entire busbar structure. The segmented design enhances reliability by isolating potential failure points while maintaining overall structural integrity.
Solution Approach 2:
The sub-busbars are designed with flexible connections that allow relative movement between them. This dynamic capability enables the busbar system to adapt to thermal cycling and mechanical stresses during assembly and operation, preventing rigid stress concentration that leads to micro cracks, while maintaining a relatively simple overall structure.
3Ease of repair
If traditional electrode structures are used, then manufacturing is simple, but cold soldering occurs leading to high repair rates
Solution Approach 1:
The multi-sub-busbar structure provides multiple contact zones within the electrode pad area, increasing the probability of successful soldering. If one contact point has insufficient solder, other contact points maintain electrical connectivity, reducing cold soldering defects and lowering repair rates while maintaining manufacturing simplicity.
Solution Approach 2:
The invention changes the geometric parameters of the busbar structure by introducing multiple sub-busbars with specific width and spacing dimensions. This parameter optimization increases the effective soldering area and improves wetting characteristics, enhancing soldering precision and reducing defects without significantly complicating the manufacturing process.
Data Source
AI summary
An electrode structure, a solar cell, and a photovoltaic module are provided. The electrode structure includes: busbars extending along a first direction and each including two sub-busbars arranged opposite to each other along a second direction intersecting with the first direction, each of the sub-busbars includes first sub-portions and second sub-portions that are spaced at intervals; fingers extending along the second direction and arranged at two sides of the busbars, the fingers are connected to the sub-busbars; and electrode pads sandwiched between the first sub-portions of the two sub-busbars and connected to the first sub-portions, the first sub-portion of at least one of the sub-busbars protrude towards a side away from the electrode pads.