PCB Laser Blocking Layer for Safe Battery Cell Welding

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Solution Overview

Problem

In laser welding of printed circuit boards (PCBs), the depth of focus (DOF) of the laser can cause unintended damage to internal circuits if the laser penetrates beyond the intended weld spot, especially when the interlayer thickness of the PCB is small.

Innovation Solution

A PCB design that includes a laser blocking portion in the second layer under the first layer, positioned at the same location as the weld spot, which reflects or blocks the laser during welding, preventing it from affecting underlying circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If laser welding is used to weld electrode lead to PCB weld spot, then welding efficiency and mechanical properties are improved, but internal circuits on lower layers may be damaged when DOF is large or laser is out of focus

Engineering Contradiction:

Improvewelding efficiencyVSAvoidlaser damage to internal circuits

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

A laser blocking portion is introduced as an intermediary element between the weld spot and the internal circuits on lower layers. This blocking portion selectively intercepts excess laser energy that would otherwise penetrate through the PCB layers, preventing damage to internal circuits while allowing the laser welding process to proceed efficiently.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the potentially harmful effect of excessive laser penetration into a beneficial protective function. By strategically placing a laser blocking portion, the harmful laser energy that would damage internal circuits is redirected to serve as a protective barrier, effectively shielding vulnerable circuits while maintaining welding effectiveness.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Volume of moving object

If interlayer thickness of PCB is reduced to make PCB thinner, then battery assembly compactness is improved, but laser penetration risk to lower layers increases

Engineering Contradiction:

ImprovePCB thicknessVSAvoidlaser penetration to lower layers

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent addresses the thickness reduction problem by introducing a protective element in the vertical dimension (z-axis). The laser blocking portion is positioned on a lower layer beneath the weld spot, creating a protective barrier in the depth dimension that prevents laser penetration without increasing the overall PCB thickness, thus maintaining compactness while enhancing safety.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Object-affected harmful factors

If empty space is left on lower layer under weld spot to prevent laser damage, then circuit damage is prevented, but PCB area utilization is reduced

Engineering Contradiction:

Improvecircuit damage preventionVSAvoidPCB area utilization

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

Instead of leaving empty spaces on the lower layer to protect circuits (the conventional approach), the patent inverts the strategy by actively placing a laser blocking portion on the lower layer. This blocking portion positively protects circuits by intercepting laser energy, allowing continuous circuit patterns to be formed on the lower layer without creating empty spaces, thus maximizing PCB area utilization.

Inventive Principle:

Principle #13The other way round (Inversion)

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

The laser blocking portion effectively prevents damage to internal circuits by reflecting or blocking the laser, ensuring accurate welding without damaging underlying layers, thereby enhancing the safety and reliability of battery cell assemblies.

Implementation Method 1

the laser blocking portion includes a material configured to reflect a laser radiated for welding at the weld spot or to prevent the laser from passing therethrough

Methodology Applied

Scientific EffectLaser reflection: Reflection

Data Source

PatentUS20250194003A1PCB including laser blocking portion and battery cell assembly including the same

Publication Date: 2025.06.12 LG ENERGY SOLUTION LTD

AI summary

A PCB, a cell battery assembly including the PCB, and a welding method using the PCB are discussed. The PCB may include a first layer including a weld spot for laser welding, and a laser blocking portion included in a second layer disposed under the first layer. The laser blocking portion may be located at a same position as the weld spot in a direction in which the first layer and the second layer are stacked. The laser blocking portion may include a material configured to reflect a laser radiated for welding at the weld spot or prevent the laser from passing therethrough while the weld spot is being welded.