Surface-Mount Component Back-Surface Terminals Solder Alignment
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Solution Overview
Problem
In electronic circuit devices with small surface-mount components, soldering defects due to solder non-wetting phenomena are difficult to detect, especially when connection terminals are on the back surface, leading to potential misregistration and reduced solder wettability with lead-free solder.
Innovation Solution
The design includes standard position indication marks on the circuit substrate to guide the alignment of back-surface connection terminals of surface-mount components, with inter-electrode pitches on the substrate being smaller than inter-terminal pitches, allowing visual or image recognition to detect misalignment and correct solder application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If connection terminals are formed on the back surface of the surface-mount component to reduce footprint, then miniaturization is improved, but detection of soldering defects becomes difficult
Solution Approach 1:
The patent inverts the conventional approach by forming connection terminals on the back surface of the surface-mount component instead of the front surface. This inversion reduces the footprint while enabling soldering defect detection through the transparent substrate, as the solder joints become visible from the front surface during inspection.
Solution Approach 2:
The transparent substrate acts as an intermediary that enables optical detection of soldering defects. By making the substrate transparent, the inspection system can visually detect solder non-wetting and other defects through the substrate without needing to access the back surface directly, thus solving the detection difficulty caused by back-surface terminal configuration.
2Area of stationary object
If electrode pad area is reduced for smaller components, then miniaturization is improved, but solder paste transfer becomes difficult leading to solder non-wetting
Solution Approach 1:
The patent introduces asymmetric design elements including misregistration indication marks positioned at specific locations and differential pitch between electrode pads and connection terminals. This asymmetry creates a self-alignment mechanism during soldering that compensates for the reduced electrode pad area, ensuring reliable solder joint formation even with smaller pads.
Solution Approach 2:
The patent changes the pitch parameters between electrode pads and connection terminals, with the pitch between electrode pads being different from the pitch between connection terminals. This parameter difference, combined with the transparent substrate and misregistration marks, enables detection and correction of positioning errors that could lead to solder non-wetting on reduced-size electrode pads.
3Manufacturing precision
If self-alignment effect is used to move component to correct position, then positioning accuracy is improved, but misregistration cannot be detected when all electrodes solder successfully
Solution Approach 1:
The patent implements a feedback mechanism through misregistration indication marks that provide visual information about component positioning. Even when the self-alignment effect successfully moves the component to the correct position, the misregistration marks reveal whether initial misregistration occurred and was corrected, preventing loss of defect information.
Solution Approach 2:
The misregistration indication marks are prepared in advance on the substrate before soldering. These marks predict potential misregistration issues, allowing the system to detect and flag positioning problems before they result in defective solder joints, thus preventing information loss about potential defects.
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 enables effective detection and correction of soldering defects, ensuring high-density circuit miniaturization without defective items, even with lead-free solder, by utilizing self-alignment effects to maintain proper component positioning.
Implementation Method 1
connected with heated solder
Implementation Method 2
heated solder
Implementation Method 3
solder material is not applied to a solder surface
Data Source
AI summary
A surface-mount component (10A) having a pair of connection terminals (12a, 12b) with an inter-terminal pitch L2 therebetween is mounted on a circuit substrate (20A) having a pair of electrode pads (22a, 22b) with an inter-electrode pitch L1 therebetween (L2>L1). Standard position indication marks (23) are formed on the circuit substrate (20A). When heating is performed under a state in which solder non-wetting of the left electrode pad (22a) occurs, the solder applied to the right electrode pad (22b) solder connects the right electrode pad (22b) and the connection terminal (12b), and the surface-mount component (10A) is attracted to the left and is offset or displaced from the standard position indication marks (23) by an offset dimension δ7. If the solder is applied to the left and right electrode pads (22a, 22b), there is no offset dimension.