For the best results, a thermocouple should be placed underneath the device making direct contact with the terminations. Special attention should be given to BGAs. An adhesive, such as Chipbonder, ensuring residual glue is not found between mating surfaces.High temperature solder to secure the thermocouple to the component lead.Quite often EMS providers will tape these in place but, unfortunately, there is a risk they lift during the process, which results in the air temperature being measured rather than board and lead temperature.įor a secure connection, we recommend applying: a transformer, ball grid array (BGA) and passive devices.ĭependent on the size of the PCBA, it is recommended that between three and six thermocouples are attached and it's critical they are connected properly. These should be attached to a range of components with varying degrees of heat dissipation – i.e. The NPI engineer will attach thermocouples to multiple locations across the sample board. If one isn't provided the NPI engineer may request one so it can be used during the set-up process. Ideally, the OEM will have provided their assembly partner with a populated PCBA. Using their skill, judgement and experience, the NPI engineer will select the profile and temperature settings they believe suits the new assembly the best. One dedicated to assemblies that contain sensitive parts and require lower temperatures.One dedicated to densely populated assemblies with elevated temperatures.Time taken to perfect the baseline profile will pay dividends as most assemblies will then fall within one of these.
Some EMS providers will have taken time to develop a range of "baseline" profiles, which can then be selected depending on the PCBA they are working on. The NPI engineer will usually start the process by selecting an oven profile they have used before and have stored on their system. So how do EMS companies go about creating the perfect surface mount (SMT) reflow oven profile? Let's find out. If you fail to profile the oven correctly, then all of the hard work and effort that has gone into loading feeders, programming the machines, optimizing the build and then running the production line will be wasted. However, in our opinion, one step that can make all of the difference when it comes to quality and consistency is reflow. While electronics manufacturing services (EMS) providers will have their own preference when it comes to machine type and brand, broadly speaking, the process steps they go through to produce PCBAs are the same. Although some original equipment manufacturers (OEMs) view printed circuit board assemblies (PCBAs) as commodity items, consistently producing them in volume takes time to perfect.
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