SPI

Well, if your operators can setup the stencil printing exactly the same all the time, then you won't need it. To me, SPI is more of consistence check more than quality check. It would be a lot more easier to troubleshoot a issue if you know you having a very reliable process that doesn't give you all kinds of variable results.

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"Must Have" is when it becomes a requirement from a customer. It is utterly impossible to inspect every solder deposit by eye on any board layout that is even moderately busy. I have lived without SPI and then implemented it across multiple lines.

I would never recommend not having SPI unless your business model allows it.

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Achieving high reliability and high efficiency in SMT process (Surface Mount Technology) assembly has always been the goal of electronics manufacturers expecting consistency. It depends on the optimization of every detail of the whole process. For SMT assembly, it was concluded that 64% of the defects were due to incorrect solder paste printing. Also, defects lead to low reliability of the product, reducing its performance. Therefore, high performance solder paste printing is very necessary to minimize the possibility of low quality.

Inspection is a must for SMT assembly requirements. At present, the commonly used inspections include naked eye inspection, AOI (Automated Optical Inspection), and X-ray inspection. To prevent improper solder paste printing from degrading the performance of the final product, Solder Paste Inspection (SPI) should be performed after soldering the solder paste printing during SMT assembly.

Based on 16 years of electronic manufacturing experience, GOLDLANDSMT company's deep concern for product reliability has also won a good reputation from many customers. GOLDLANDSMT's one-stop SMT equipment procurement to help customers provide the best solutions. The smooth operation of smt patch assembly originates from the strict process control in the workshop.

SPI usually occurs after solder paste printing in order to detect printing defects in time so that they can be corrected or eliminated before placement. Or, there may be more defects or even disasters at a later stage.

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Advantages of SPI

1. Reduce defects

SPI was first used to reduce defects caused by improperly printed solder paste. Therefore, the primary advantage of SPI is its ability to reduce defects. Defects have always been a major problem when it comes to SMT assembly. And the reduction of their number will lay a solid foundation for the high reliability of the product.

2. High efficiency

Think of the traditional SMT assembly process rework model. Defects will not be exposed unless inspection is performed, usually after reflow soldering. Typically, AOI or X-ray inspection is used to find defects and then rework. If SPI is used, defects can be found at the beginning of the SMT assembly process after the solder paste has been printed. As soon as incorrect solder paste printing is found, rework can be performed immediately to obtain high-quality solder paste printing. More time will be saved and manufacturing efficiency will be improved.

3. Low cost

For the application of SPI machine, low cost has two meanings. On the one hand, time costs will be reduced as defects can be found at an early stage of the SMT assembly process and rework can be done in time. On the other hand, funding is also reduced because defects can be stopped earlier to avoid delaying early-stage defects into later stages of manufacturing, leading to threatening defects.

4. High reliability

As noted in the first point, most defects in SMT assembled products originate from low-quality solder paste printing. Now that SPI is good for reducing defects, it will help improve product reliability through tight control over the source of defects.

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I ran a SMT production line with and without SPI. I was also charged with gathering the time and defect metrics when we got our new SPI machine, comparing before and after implementation. It saved time on the printer because it didn't have to handle the inspection itself; just lined up the fiducials and ran. That also freed the employee from having to manually scan the board and allowed them to focus on other tasks. Across the board on all assemblies, we saw a 12% minimum time reduction (board in printer to end of line inspection) by distributing that task to the SPI machine. And solder defects basically disappeared instantly because they were caught right away so printer adjustments could be tailored exactly as needed. I'm not a salesperson, so I won't say which one I use. But I'll post it if people want to know.

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It is just a quality check, so it is not a MUST per say. It is really nice to have. To benefit from it though, you should have a good understanding of it and monitor results constantly. SPI really help you understand your printing process and investigate existing issues caused by improper paste deposit.

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BGAs are semi difficult, imagine spending a full shift looking at the same 3 BGA groups and you can see how an operator would get distracted and let marginal results through.

I noticed great benefits with micro BGA components. When experimenting with SPI I had my usual inspection lady check over a board with 1 micro BGA (300 pads) and 3 BGAs (about 1000 pads) not only was SPI faster but it caught multiple boards with substantially insufficient solder paste deposits.

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