PCB Alignment Channels for Reflow Soldering Positioning
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Solution Overview
Problem
High-volume surface mount technology (SMT) processes face challenges in maintaining accurate positioning and alignment of components on printed circuit boards (PCBs) during reflow soldering, as components can shift due to liquid solder, leading to potential functional failures and manufacturing issues.
Innovation Solution
Incorporating channels in the conductive layer of the PCB substrate, which utilize surface tension and capillary forces of solder paste to prevent shifting, and employing an image processing system to facilitate precise positioning and alignment using these channels, solder masks, and alignment marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If automated placement machines are used to position components on PCB, then productivity is improved, but manufacturing precision deteriorates due to placement errors and component shifting during reflow
Solution Approach 1:
Alignment channels are pre-formed in the conductive layer before component placement. These channels serve as preliminary positioning guides that constrain component locations before the reflow process, preventing placement errors from causing misalignment. The channels are created through photolithography and etching processes prior to assembly.
Solution Approach 2:
The alignment channels act as an intermediary structure between the placement machine and the final component position. Rather than relying solely on the placement machine's precision, the channels provide a physical reference framework that mediates the positioning process, allowing standard placement equipment to achieve higher effective accuracy.
2Strength
If reflow soldering is performed to bond components, then bonding strength is improved, but component stability deteriorates due to shifting from liquid solder
Solution Approach 1:
Alignment channels are created in advance to counteract the harmful effect of solder-induced component shifting. During reflow, the channels physically constrain the components, preventing them from moving despite the liquid solder's tendency to cause displacement. This preliminary structural constraint opposes the destabilizing force of molten solder.
Solution Approach 2:
The conductive layer is modified locally at specific component positions by forming channels only where needed for alignment. This localized modification provides positioning constraints precisely at critical locations without affecting the overall bonding process or requiring changes to the entire PCB structure.
3Manufacturing precision
If alignment channels are added to the conductive layer, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The alignment channel structure replaces complex mechanical positioning systems that would otherwise be needed to achieve high precision. Instead of using sophisticated placement machinery or complex fixture systems, the patent uses a simple etched channel pattern that provides mechanical guidance through the solder reflow process itself.
Solution Approach 2:
The conductive layer's physical structure is modified by changing its surface topology - adding channels through photolithography and etching processes. This parameter change (from flat to channelled surface) provides alignment functionality without requiring additional components or complex assemblies, simply altering the existing layer's geometry.
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 solution significantly reduces component shifting during reflow soldering, achieving high accuracy in positioning and alignment, with relative position errors maintained at less than 20 μm, ensuring proper bonding and functionality of the assembled circuit boards.
Implementation Method 1
The channels can help reduce or prevent shifting of the component during reflow soldering through surface tension/capillary forces of the solder paste material in the channels
Implementation Method 2
The channels can help reduce or prevent shifting of the component during reflow soldering through surface tension/capillary forces of the solder paste material in the channels
Data Source
AI summary
One or more channels are provided in the surface of a conductive layer of a PCB substrate in an area on which a component is to be placed. The channels can help reduce or prevent shifting of the component during reflow soldering through surface tension/capillary forces of the solder paste material in the channels. Such channels also can be used, for example, by an image processing system to facilitate accurate positioning and/or alignment of the component. The image processing system can use the location of the channels alone, or in combination with other features such as a solder mask or other alignment marks, to position and/or align the component with high accuracy.