/SPI solder paste testing equipment application and discussion
With the maturity of solder paste inspection (SPI) technology, solder paste printing inspection will become the standard for prototype pcb manufacturing production lines. However, there are several problems with the current application:
(1) The data of the SPI device is not closely related to the solder pass-through rate, and there are often problems with the detection, but there is no problem with the soldering.
(2) How to set testing basis for solder paste thickness, area and volume? If the setting range is small, the alarm is frequent and the false alarm rate is high; if the setting is wide, it seems to be useless.
How prototype PCB manufacturers make full use SPI detection equipment becomes a problem. The following discussion on this issue is purely personal and is for the reader’s reference only.
First we must be clear:
(1) There are many factors, including component package quality, PCB design, solder paste, stencil, print quality, temperature profile, etc., which may result in poor soldering. The poor soldering caused by printing is mainly concentrated on soldering defects related to the amount of solder paste, such as bridging, open soldering, ball socket, tombstone, solder ball etc. Therefore, poor printing is only part of the cause of poor soldering, and it is only related to partial soldering defects.
(2) Each type of package has different sensitivity to solder paste printing quality. 0.4mm QFP is extremely sensitive to solder paste thickness, but PLCC is not sensitive at all.
Knowing these two points, we basically understand our needs. We need to focus on fine-pitch components, and pay attention to the solder paste quality data on each pcb pad.
If the SPI can selectively output the data we need and give an alarm in a targeted manner, then frequent manual processing can be reduced.
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