SMT007 Magazine

SMT-May2016

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48 SMT Magazine • May 2016 algorithm technology so that we had a more accurate prediction to provide our customers a better tool. Las Marias: What is the importance of knowing that convection rate? Bouchard: In a reflow oven, the heat transfer is created by a handful of things. To keep it sim- ple, we have radiation, conduction and what's called forced convection. Forced convection is the dominant heat transfer method inside the oven that is directed onto the product. The convection rate, in particular, is one of the major heat transfer components. By not in- cluding the convection rate, the algorithm has to use a fixed heat transfer rate that doesn't re- flect the convection rate that's in the oven. For example, in our systems, the convection is very tightly controlled. Changes in convection can impact a number of things—like the uniformity on the PCB—or it can impact the actual heated zone set points and conveyor speed. All these things work together, and in par- ticular BTU has a very precise convection con- trol system that creates very repeatable process. From one machine to another, or one site to another, you dial in a recipe in our equipment and it can be transferred anywhere in the world. This is the importance of a convection rate. By changing the convection rate, it allows us to have a very accurate prediction of the thermal profile. Las Marias: Definitely it ensures the quality of the product that goes out of the oven. Bouchard: It makes it repeatable. What we're focused on here is to help reduce set up time. If a customer had a new PCB that they need to setup the oven and the reflow profile for, the process has typically been trial and error. Many of the customers today don't have the same ex- perienced staff that they might have had in the past. Someone who can look at the board and say, "Oh, this is similar to another board and I think I get in the same ball park." The recipe generator reduces the set up time; it reduces mistakes in setting this up, and it improves yield because you're not putting in a bad recipe, even a bad starting recipe. There are a number of benefits on having this capability. Las Marias: It also reduces the cycle time of the process, right? According to one our surveys, re- flow is one of the processes in the assembly line that is a pain point for some companies. Bouchard: It's certainly a step in the right di- rection. What this tool is intended to do is to create a starting point. By doing that, you re- duce the down time associated with setting up a new PCB. That's another benefit that comes from the fact that you don't have the downtime associated with profiling. The downtime means that you're not running product with the tool. If you spend time taking your machine out of production to set up a new profile, you're losing production time. Time is money. This is a tool that's designed to reduce that set up time so you have more uptime in production. Las Marias: In our recent survey on automation and reducing handling errors, one of the systems or processes in the assembly that readers said had room for improvement is reflow soldering. Definite- REducing SEtuP tiME to PRovidE MoRE uPtiME in PRoduction Bob Bouchard

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