DIY Reflow Ovens
Since the inception of surface mount devices, there has been a considerable gap in technology between the consumer industry and educational/hobbyist based electronic groups. Originally, surface mount devices were a means for industry to consolidate board space and reduce cost slightly. At that point in time, educational and hobbyist based groups unanimously used through-hole components because of their ease of use and availability. However, over the years, surface mount component technology has increased rapidly in both availability, size reduction, and cost reduction. Most modern consumer electronic products all use SMT(Surface Mount Technology) components that required machines to place and solder all the parts. This has been an increasing issue for hobbyists as SMT parts have become smaller and smaller. Meanwhile, suppliers have continually eliminated their production of through-hole based components due to the lack of demand. Many universities as well as hobbyist groups have fallen considerably behind modern technology as a result of this migration industry migration to SMT devices. One unique recent solution to this growing issue has been the development of DIY reflow ovens.
Before we go into specifics on how DIY reflow oven is produced, its important to understand just what a reflow oven is. A reflow oven is an oven that is used to flow solder-paste on PCB SMT assemblies. Starting off in an SMT production line, commercial PCBs usually have a metal stencil cutout made for all their various component pads. This stencil will allow the application of solder paste specifically to the exposed component pads. Solder paste itself is compound composed of solder particles that are suspended in liquid flux forming an adhesive that will become solid when heated. Components are then placed on top of the solder-paste and baked in a reflow oven to form a solid connection. An example of components industry SMT as well as a PCB board reflow can be observed in the following videos.
Hobbyists and educational institutions obviously cannot afford to purchase the mammoth part placement machines or reflow ovens that are used currently in the industry. Consequently, makeshift ovens have popped up all over the place using a variety of substitutes such as toasters, skillets, and ovens. Due the fact that these ovens are a diversion from industry, there is no fixed standard as to how to go about it. All that is technically required in order for a reflow to occur is to exceed a temperature of roughly 200C. At 200C in temperature, most forms of solder will begin to flow. While these devices may be able to flow solder, their safety and reliability are put into question. Hence, the quality and reliability of the oven are completely up to the builder and the features that they decide to implement. For example, some DIY reflow ovens will implement advance sensors such as multiple thermocouples for heat control, solid state relays for power control, and convection fans for even heat distribution. The features that are implemented generally depend on the designer's budget and emphasis on component safety. In regards to safety, components are rated based upon durations of high temperature exposure and going above these levels can lead to component destruction. As a result of this, industry reflow ovens follow a strict reflow oven profile. Likewise, a DIY oven is also graded based upon how closely it can follow a given profile. To give you an idea of what a reflow profile may look like, see the below image.
Impact of DIY Reflow Ovens
The impact of DIY reflow ovens has resulted in a huge rebirth of hobbyist based electronics. Many hobbyist sites such as http://www.sparkfun.com/ are now daring to offer a majority of surface-mount device based kits as well as offering training on how to produce your own reflow process. Likewise, DIY reflow ovens have brought many additional people into the hobbyist field as a result of the new and advance applications that have become possible. Applications such as USB, Ethernet, and WIFI are all unique applications that a DIY reflow oven significantly simplifies. Many educational institutions are also reaping the benefits of DIY reflow ovens. With the assistance of DIY ovens, universities can expect students to be able to utilize SMT components. In addition, universities are able to bring in more advance applications into labs that were previously difficult. Overall, the impact of DIY reflow ovens have resulted significant rebirth in hobbyists/education institutions and it will be impressive to see long term benefits that it will provide.
Examples of DIY Ovens:
http://www.ustr.net/smt/oven.htm
http://www.43oh.com/forum/viewtopic.php?f=9&t=2035
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