The main purpose of SMT assembly is to place SMD components onto PCB pads correctly and in high precision. Some of companies take one pad as a “spot”, and some take two pads as a “spot”. Let us take one pad as a “spot” for example in this passage. Actually, we only have to figure out the total quantities of PCB pads. But, we will meet some special components, such as inductance, big capacitor and IC, which should be calculated separately. According to experience, there are 10 spots for inductance. 50% discount of IC pins (for example, there are 20 spots for 40 pins IC). In this way, we can easily work out the total quantities of PCB pads until now.
Next, we have to confirm the unit price. In the marketplace, there is different price for each spot, generally from 0.01~0.03 RMB/spot, which is determined by difficulty and quality of PCB assembly process. For cheap price, there are probably no AOI/ICT test and incoming material inspection. So the quality of batch order would be hardly to guarantee. In this case, there will be big potential risk of product uniformity and stability in the future. For a little bit higher price, the SMT manufacturer would like to control good quality process and provide better delivery lead time and outstanding services. Therefore, customers should select the SMT assembly manufacturer on basis of their product positioning and technical requirements.
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