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  How to make the SMT production process the best?

How to make the SMT production process the best?

                           -The requirements of surface mount components


  Surface mount technology referred to as SMT, In order to obtain a high-quality, stable performance, long life PCB assembly circuit board from the SMT process technology, component itself checking must be carried out before components mounting, otherwise a lot of implicit quality problem will stay in the following assembly or welding processes (especially hand soldering). The implicit quality factor can't reveal from the surface, they will change over time,product using or environmental conditions, and finally evolved into a quality failure. Therefore, we must attach great importance to the quality of their components and technology to them by the various assembly and welding requirements. The following are the requirements from a process point of view of the proposed components.

① For surface mount components, their pin coplanarity issue is crucial. If a QFP device coplanarity damaged, and the reliability of welded points is not guaranteed. Thus, before components installation, device pin coplanarity problems must be requested, otherwise the quality can not be guaranteed in the process behind.

② Solder coating thickness of components solder pin or end should meet the technical requirements, generally recommended thickness should be greater than 8um, for solder coating the tin content should be between 60% to 63%.

③ Considering the weldability, moisture absorption and other issues, the assembly and welding of surface mount components should be completed within 48h after opening

Surface mount components dimensional tolerances should meet the relevant requirements of the military standard "GJB3243" , should meet the requirements of pad design, assembly, welding and other processes. they tend to occur pad size errors in the size of the pad can not meet the technical condition requirements when choose the components in the system. do not take reluctantly welding, even soldering problem does not occur in the short term, but an assembly welding process which does not meet the conditions will eventually lead to product quality defects.

⑤ surface mount components should be able to withstand at least five welding cycles heating at 215°C ,Generally, each welding conditions should withstand vapor phase reflow soldering is to 215°C, 60s;. IR reflow time to 230°C, 20s; wave soldering is 260°C, 10s, could refer QJ3086 standards.

⑥Components should stay at least 4min in the solvent (such as HCFC)  washing temperature(approximately 40°C). in ultrasonic cleaning conditions, the ability of frequency 40kHz;. Stay at least 1min per liter ultrasonic power of 20W, don't effect the right performance and reliability, components mark do not fall off.

⑦ All the surface mount components used in assembly should be according to relevant regulations, aging, testing and inspection products.

⑧Static-sensitive components should operate follow anti-static requirements from the design documents and technical documents

   Located in Shenzhen, with over 10 years experience in surface mount pcb assembly service, MOKO TECHNOLOGY always make the surface mount technology follow the ISO standard. with the ISO9001:2008 certificate,we do the IQC for each component also we have our own supplier control system to make sure each component stable during the production. we have our own engineer team to control each status, from the components choice,surface mounting technology till the final product testing, each step have their own operating instructions,we always carry on the management concept of "Quality superior, Service supreme, Reputation first" to provide the best service in the production and sales for our global customers. We are looking forward to being your long term partner! 

Keywords:surface mount technology,smt,pcb assembly,surface mount components