PCB Power Hole Segmentation for Lead-Free Solder Filling
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Solution Overview
Problem
Thick multi-layer printed circuit boards (PCBs) face difficulties in completely filling plated-through-holes (PTHs) during the soldering process due to heat sinking effects from copper layers, leading to premature solder freezing and incomplete connections, especially when using lead-free solder.
Innovation Solution
Configuring the electrically conductive layers within the PCB to minimize heat sinking by not directly contacting all internal ground or power planes with the PTHs, allowing molten solder to completely fill the holes before freezing, and optimizing the distribution of conductive material between ground and power planes based on predetermined ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple copper layers are used to provide adequate ground and power connections, then electrical conductive capacity is improved, but heat sinking effect increases causing solder to freeze prematurely
Solution Approach 1:
The patent segments the connection holes into two distinct types: signal holes that connect to both ground and power layers, and power holes that connect only to power layers. This segmentation prevents power holes from contacting ground layers, thereby reducing the total copper surface area that acts as heat sink and preventing premature solder freezing while maintaining adequate electrical conductive capacity through proper layer allocation.
Solution Approach 2:
The patent applies different connection configurations to different types of holes based on their function. Signal holes use a configuration that connects to both ground and power layers for balanced electrical performance, while power holes use a configuration that connects only to power layers to minimize heat sinking. This local quality approach optimizes each hole's electrical and thermal characteristics according to its specific function.
2Reliability
If PCB thickness and copper sheet weight increase to handle higher power and signal requirements, then electrical performance is improved, but solder filling completeness deteriorates
Solution Approach 1:
The patent segments the internal layers into separate ground layers and power layers, and segments the connection holes into signal holes and power holes. This allows thick PCBs with multiple copper layers to maintain high electrical performance while power holes are configured to minimize heat sinking, ensuring complete solder filling even in thick boards with substantial copper content.
Solution Approach 2:
The patent changes the electrical connection parameters by configuring power holes to connect only to power layers rather than both ground and power layers. This parameter change reduces the effective copper surface area contact for power holes, thereby reducing heat sinking effect and enabling complete solder filling in thick PCBs with high copper weight while maintaining electrical performance through proper layer allocation.
3Stability of the object's composition
If all internal ground and power planes are connected to through-holes, then electrical stability is improved, but heat dissipation increases causing connection integrity to deteriorate
Solution Approach 1:
The patent segments the internal planes into separate ground planes and power planes, and segments the through-holes into signal holes and power holes. This segmentation allows ground planes to be connected to signal holes for electrical stability, while power holes connect only to power planes, minimizing heat dissipation and ensuring complete solder filling for reliable power connections.
Solution Approach 2:
The patent applies different connection strategies to different hole types: signal holes connect to both ground and power layers for electrical stability, while power holes connect only to power layers to minimize heat dissipation. This local quality differentiation ensures that electrical stability is maintained where needed while connection integrity is preserved by reducing heat sinking at power connections.
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
Ensures complete filling of PTHs with solder, enhancing mechanical and electrical reliability of connections by reducing heat dissipation and maintaining the integrity of solder joints.
Implementation Method 1
the molten solder fills the holes around the pins by capillary action
Implementation Method 2
The multiple layers of copper sheets may conduct heat away from the molten solder (i.e., act as heat sinks), causing the solder to freeze prematurely
Implementation Method 3
The preheating zone consists of convection heaters, which blow hot air onto the PCB to increase its temperature
Implementation Method 4
the solder waves contact the bottom of the board, and stick to the solder pads and component leads by surface tension
Data Source
AI summary
Apparatuses and methods that provide for enhanced connections between PTHs of multi-layer PCBs and electronic component leads, pins or the like, are described herein. The apparatuses and methods improve the likelihood that the PTHs are completely filled with solder thereby advantageously allowing the PCBs to exhibit high mechanical and electrical reliability. Complete filling of PTHs is achieved by configuring the electrically conductive layers within the multi-layer PCB stack in a manner that reduces the heat sinking effects of the layers during the soldering process. In this regard, the PTHs may not directly contact all of the internal ground or power planes, so the heat sinking or heat transfer effects are reduced. This feature enables molten solder to substantially or completely fill an entire PTH before freezing.