Battery Pack PCB Layout for Single-Side Traces and Strap Soldering
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Solution Overview
Problem
The production of battery packs for cordless power tools is costly due to the need for copper etching on both sides of printed circuit boards (PCBs) to create traces and test points, which wastes material and increases production time.
Innovation Solution
A battery pack design where all traces and components are on a single side of the PCB, using vias to connect components on one side to the other, allowing for single-pass wave soldering of battery cell straps without the need for copper etching on the top side, reducing material waste and assembly time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper etching is performed on both sides of the PCB to create traces and test points, then electrical connectivity and testing capability are improved, but material waste and production cost increase
Solution Approach 1:
The patent moves all electrical traces from the top side of the PCB to the bottom side, utilizing the third dimension (via holes penetrating through the board) to establish electrical connections. This dimensional transition eliminates the need for top-side copper traces while maintaining full electrical connectivity through the via system.
Solution Approach 2:
The patent extracts the copper etching process from the top side of the PCB, removing unnecessary copper material while preserving all essential electrical functions. By placing only connection features (via holes) on the top side and all traces on the bottom side, the design eliminates redundant copper usage.
2Reliability
If copper etching is performed on both sides of the PCB, then electrical connectivity is improved, but production time increases
Solution Approach 1:
The patent utilizes via holes (vertical dimension) to establish electrical connections between layers, eliminating the need for time-consuming top-side copper etching and subsequent multi-layer alignment processes. All trace routing is consolidated on the bottom side, simplifying the manufacturing sequence.
Solution Approach 2:
The patent performs all copper etching and trace formation on the bottom side before final assembly, allowing for more efficient process sequencing. The top side requires only via hole formation, which can be done as a preliminary step before the main trace etching process.
3Ease of manufacture
If all traces and components are placed on a single side of the PCB, then material cost and assembly time are reduced, but connection complexity increases
Solution Approach 1:
The patent resolves connection complexity by utilizing the vertical dimension (via holes) to bridge the single-sided trace layout with the battery strap connections. This three-dimensional approach simplifies the two-dimensional layout while maintaining all necessary electrical connections.
Solution Approach 2:
The patent introduces vias as intermediary elements that mediate between the single-sided PCB traces and the battery strap connection points. These via holes serve as intermediate connection features that eliminate the need for complex multi-layer trace routing while maintaining electrical connectivity.
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 material costs and assembly time by eliminating the need for copper etching on the top side of the PCB, enhancing manufacturing efficiency and cost-effectiveness.
Implementation Method 1
the battery strap can be soldered to the via (and electrically coupled to the trace) after the PCB has been combined with the cell holder
Data Source
AI summary
A battery pack comprises a set of battery cells, a battery cell holder holding the battery cells, at least one battery strap having a first end connected to a terminal of one of the battery cells and a second end extending from the battery cell holder, a printed circuit board having a first side and a second side, components mounted on the second side of the printed circuit board, a trace on the second side of the printed circuit board extending from one components to a contact connected to the trace and mated with the second end of the at least one battery strap. Multiple vias extend from the first side to the second side, and the contact comprises a first portion having a through hole and a leg integrally formed with and approximately perpendicular to the first portion, the leg extending from the first side of the PCB to the second side of the PCB through a first via, the trace extending from the first via, the leg soldered to the second side of the PCB and the via and the through hole aligned with a second via adjacent to the first via, the through hole sized and configured to receive a PCB end of the strap, the PCB end of the strap soldered to the contact.