Solder Paste Transfer Control via Subarea Segmentation
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Solution Overview
Problem
The PCB printing process is critical in electronic assembly manufacturing, with 50-70% of defects occurring due to unreliable solder paste transfer through stencil apertures, leading to high rework costs and inefficiencies, as existing methods fail to accurately predict solder paste deposition through small apertures.
Innovation Solution
The method identifies and excludes subareas with low repeatability in solder paste transfer based on PCB and stencil design data, focusing on areas with high repeatability to determine reliable control parameters, using Gerber data to calculate area ratios and measure characteristic quantities like volume, height, planarity, position, and rotational orientation of solder paste deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If solder paste transfer is controlled through small aperture stencil areas, then complete PCB coverage is achieved, but repeatability and reliability of solder paste deposition deteriorate
Solution Approach 1:
The PCB surface is segmented into first subareas (with poor repeatability) and second subareas (with good repeatability) based on aperture area ratios. This segmentation allows the system to treat different regions differently, excluding problematic areas from control parameter determination while maintaining overall process coverage.
Solution Approach 2:
Different quality standards are applied to different regions of the PCB. Second subareas with high repeatability are used for determining control parameters, while first subareas with low repeatability are excluded from this determination. This local quality approach ensures that control parameters are derived from reliable data sources.
2Quantity of substance
If all subareas are used to determine control parameters, then comprehensive data is collected, but measurement precision and reliability of control parameters deteriorate due to inclusion of low-repeatability areas
Solution Approach 1:
The method extracts and excludes first subareas with poor repeatability from the data set used for determining control parameters. By taking out these problematic regions, the system ensures that control parameters are determined solely from second subareas with high repeatability, thereby maintaining measurement precision and parameter reliability.
Solution Approach 2:
Before determining control parameters, the system performs a preliminary classification of subareas based on aperture area ratios and repeatability characteristics. This preliminary action identifies which regions are suitable for parameter determination, preventing low-repeatability areas from contaminating the control parameter data set.
3Device complexity
If traditional PCB printing control is used without subarea differentiation, then process simplicity is maintained, but manufacturing precision and defect rate worsen
Solution Approach 1:
The control system dynamically adapts by selectively using data from different subareas based on their repeatability characteristics. Rather than applying a static uniform control approach, the system dynamically determines which subareas are suitable for parameter determination, thereby improving manufacturing precision without requiring complete process redesign.
Data Source
Figure 1~2
Figure 3
AI summary
It is described a method for changing parameters for controlling a transfer of solder paste onto a printed circuit board (150, 250). The described method comprises (a) identifying first subareas (256, 258) of the printed circuit board (150, 250), which exhibit a first repeatability with respect to the amount of solder paste being supposed to be transferred onto the printed circuit board (150, 250), (b) identifying second subareas (252, 254) of the printed circuit board (150, 250), which exhibit a second repeatability with respect to the amount of solder paste being supposed to be transferred onto the printed circuit board (150, 250), wherein the first repeatability is smaller than the second repeatability, (c) transferring solder paste onto the printed circuit board (150, 250) at least at the second subareas (252, 254) of the printed circuit board (150, 250), (d) measuring the amount of solder paste which has been transferred to the second subareas (252, 254), and (e) changing the parameters for controlling a transfer of solder paste onto the printed circuit board (150, 250) in response to the measured amount of solder paste which has been transferred to the second subareas (252, 254). It is further described a corresponding processing device, a system comprising such a processing device and a computer program for controlling and/or for carrying out such a method.