Recessed Copper Layers for Thermal Insulation in PCB Soldering

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Solution Overview

Problem

Large through-hole or surface mount leaded components in power supply technology face difficulties in soldering and rework due to high temperatures leading to integrity issues like delamination, decomposition, and copper dissolution, especially with lead-free solder alloys, which require specialized equipment and result in increased scrap and reduced reliability.

Innovation Solution

The implementation of circuit card components with recessed copper layers for thermal insulation and vias surrounding through-holes to maintain heat near the soldering area, allowing efficient flow of high-temperature lead-free solders and improving electrical connectivity while minimizing heat transfer to internal layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high temperatures are used for soldering lead-free components, then solder flow is improved, but PCB integrity deteriorates due to delamination, decomposition, and copper dissolution

Engineering Contradiction:

Improvesolder joint reliabilityVSAvoidPCB integrity damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The copper layers are segmented into different levels: a first copper layer at the surface, a second copper layer recessed below the surface, and a third copper layer recessed even further. This segmentation creates thermal zones that allow heat to be concentrated where needed while protecting sensitive areas.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The copper layers are nested at different depths within the PCB structure, with each subsequent layer recessed below the previous one. This nested arrangement allows the soldering heat to pass through the first layer while the recessed second and third layers remain protected, preventing PCB damage.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Ease of manufacture

If traditional soldering processes are used for through-hole components, then manufacturing is simple, but solder fill is insufficient to meet electrical and mechanical performance characteristics

Engineering Contradiction:

Improvesoldering process simplicityVSAvoidsolder fill quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The first copper layer is configured with specific local qualities including being coplanar with the PCB surface and having optimized trace patterns. This local quality enhancement at the soldering interface improves solder wetting and fill without requiring changes to the overall manufacturing process.

Inventive Principle:

Principle #3Local quality

3Reliability

If specialized soldering equipment is used for power components, then soldering capability is improved, but device complexity and cost increase

Engineering Contradiction:

Improvesoldering capabilityVSAvoidsoldering equipment complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The PCB structure itself provides the soldering assistance through its multi-layer copper configuration. The recessed copper layers and thermal management features are built into the PCB, allowing standard soldering equipment to achieve results that would otherwise require specialized tools and processes.

Inventive Principle:

Principle #25Self-service

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 solution enhances solderability, reduces scrap, and improves the reliability of soldering processes by maintaining heat near the soldering area, allowing for efficient solder flow and improved electrical performance, even with lead-free solders, thus addressing the challenges of high-temperature soldering and rework difficulties.

Implementation Method 1

recessed copper layers for thermal insulation. Thermal insulation prevents heat conduction away from flowing solder, allowing the solder to flow freely through the through-hole

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 2

via structures may be disposed around a through-hole to provide substantially the same cross-sectional area for electrical connectivity... maintain the necessary cross-sectional area for electrical connectivity

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Data Source

PatentUS11570894B2Through-hole and surface mount printed circuit card connections for improved power component soldering

Publication Date: 2023.01.31 ROCKWELL COLLINS INC

AI summary

A system of circuit card components each include through-holes for soldering having recessed copper layers for thermal insulation. Thermal insulation prevents heat conduction away from flowing solder, allowing the solder to flow freely through the through-hole. Even high-temperature, lead-free solders may maintain the necessary temperature to flow. Different circuit layers include specialized features based on distance from a top or bottom surface. Vias surrounding the through-hole maintain the necessary cross-sectional area for electrical connectivity.