Upper-Portion 3D Solder Paste Inspection Before Reflow

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Solution Overview

Problem

Conventional solder printing inspection devices fail to detect soldering defects such as solder balls and cavities that occur after the reflow process, despite the solder paste meeting inspection criteria before reflow, due to the three-dimensional shape of the solder paste not being adequately assessed.

Innovation Solution

A solder printing inspection device that performs pre-reflow inspection by irradiating the printed circuit board with light, taking images, and obtaining three-dimensional measurement data to extract and judge the quality of the upper portion shape of the solder paste, using a neural network to reconstruct and compare shape data for accurate defect detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional three-dimensional measurement inspection is performed on solder paste, then printing position, area, height and volume can be measured, but soldering defects such as solder balls and cavities cannot be detected after reflow

Engineering Contradiction:

Improvemeasurement data accuracyVSAvoidsoldering defect detection capability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The solder paste is divided into multiple height zones (first height region and second height region), with the upper portion (second height region) being the focus of inspection. This segmentation allows the system to specifically target the critical upper portion that causes soldering defects, rather than treating the entire solder paste volume uniformly.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The inspection transitions from conventional two-dimensional or overall three-dimensional measurement to focused three-dimensional shape measurement of the upper portion only. This dimensional focus on the critical upper region enables detection of shape defects that conventional measurement methods miss, directly addressing the reliability issue.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If complete three-dimensional shape inspection of solder paste is performed, then shape quality can be assessed, but inspection complexity and processing time increase

Engineering Contradiction:

Improveshape defect detection accuracyVSAvoidinspection system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The inspection system extracts and inspects only the critical upper portion (second height region) of the solder paste, excluding the lower portion from detailed inspection. This extraction of the critical inspection target reduces data processing requirements and simplifies the inspection system while maintaining high detection accuracy for shape defects.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of performing complete three-dimensional inspection of the entire solder paste, the system performs partial inspection focused exclusively on the upper portion that causes soldering defects. This partial action approach reduces inspection complexity while achieving the necessary reliability for defect detection.

Inventive Principle:

Principle #16Partial or excessive action

3Productivity

If conventional inspection criteria are used, then printing process quality can be verified, but soldering defects after reflow remain undetected

Engineering Contradiction:

Improveinspection throughputVSAvoidsoldering defect prediction accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The inspection applies different quality assessment criteria to different height regions of the solder paste. Specifically, the upper portion (second height region) is inspected for three-dimensional shape quality to predict soldering defects, while the lower portion is not subjected to the same level of inspection. This local quality approach enables reliable defect prediction without compromising productivity.

Inventive Principle:

Principle #3Local quality

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

Enables early detection of shape defects in the solder paste that cause soldering defects, improving inspection accuracy and efficiency by reducing the need for alignment and storage of printing set information, and enhancing processing speed.

Implementation Method 1

an irradiation unit configured to irradiate a printed circuit board with a predetermined light

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 2

an imaging unit configured to take an image of the printed circuit board irradiated with the predetermined light

Methodology Applied

Scientific EffectImage formation through light capture: Photography

Data Source

PatentUS12432895B2Solder printing inspection device

Publication Date: 2025.09.30 CKD CORP

AI summary

A solder printing inspection device includes: an illumination device that irradiates, with a predetermined light, a printed circuit board on which a solder paste is printed; an imaging device that takes an image of the printed circuit board irradiated with the predetermined light and obtains image data; and a control device that: based on the image data, obtain three-dimensional measurement data of the solder paste printed on the printed circuit board, based on the three-dimensional measurement data, extracts upper portion shape data of an upper portion of the solder paste, the upper portion having a height equal to or higher than a predetermined height, and compares the upper portion shape data with a predetermined criterion and determines whether a quality of a three-dimensional shape of the upper portion of the solder paste is good or poor.