In this zone if the heat is transferred at a higher rate there is a risk of Solder-spattering,Solder-balling,oxidation of pads & termination.Where as if the heat transer is done at a lower rate there is a risk of non-activation of flux giving rise to a risk of cold solder, incomplete solder as well as void. In this zone most of the flux evaporates form the paste.A typical time range for this zone is 60 to 120 sec. Ramp refers to the rate at which temperature changes over time and which is expressed in degree per second.In a typical case it ranges between 4 degree per second and 2 degree per second.In the soak zone solder paste goes into phase change. There are two main type of thermal profile one is called Ramp-Soak-Spike (RSS) and the other is called Ramp-to-Spike (RTS) It is mandatory to control the temperature of the reflow oven very precisely in every zone in order to protect the electronic component and most importantly formation of correct solder joint through accurate chemical & thermal equation. Similar solution is achieved by ultrasonic reflow also.Ī typical reflow profile consist of four stages having preheating, soaking, reflow and cooling zone.Įach zone temperature characteristic as well as temperature requirements are different, accordingly their names are given. But availability and applicability of this is limited and hence does not provides universal solution of all the user. Vacuum reflow is the ultimate solution to the void where soldering is done in a vacuum environment and flux gases are sucked out of the joint leaving void free solder joint. But in many cases it solves the problem to a great extent. Either it calls for many trials or it reduces the amount of solder at the desired joint. Adjusting the paste volume as well as creating a space to allow the flux-gases to come out solves the problem of void.But due to geometry of the component and size of the component many a times this solution also does not work the best. One of the possible solution to the void has been stencil opening for the component affected by void. Also, availability of paste as well as change of paste and its qualification poses real challenge to the user. Lot many chemistry and combination has been brought to solve the problem.But finding one solution to resolve the problem has been difficult.If one chemistry works best for some particular joint and combination of component, it does not work for many. Solving a void problem through the chemistry of the paste has been the most worked area. In reality, the gaseous flus is supposed to come out of the joint but gets trapped and forms an area void of solder creating solder-void. Void is created in the reflow soldering, when the flux in the gaseous form gets trapped in the solder. Problem has been more serious with advent of lead free solder and has been aggravated by miniaturization of component as well as densely populated PCB with component having smallest and biggest in a very small real state of the PCB. Please refer to product section for more information.Void in the solder joint is a problem and it needs to be addressed depending upon the criticality of the joint. Note: Not all of C&K products have been tested to this profile. Thermal profile done 2 times on each part listed.Maximum time above 183☌ for 60 seconds.Reflow at a maximum of 245☌ for 10 seconds.Pre-heat to a maximum of 200☌ for 30 seconds.Thermal profile in accordance with CEI 6 / EN 6.Thermal profile done 2 times on each part tested. SMT Reflow Soldering Profile of Reference Do not immerse or spray the unsealed areas of the switches with cleaners during flux removal. Solder time is approximately 3 seconds maximum. Hand soldering and cleaning are acceptable with properly trained personnel, small diameter solder (.030-.040 in.) and low wattage soldering irons (25-40 watts max.). Care during soldering and cleaning can prevent most process contamination problems encountered.Ĭontamination can occur in both hand soldering and machine soldering processes. Switches may become intermittent, especially in low power applications, and may become open during factory testing or later in the field. Most manufacturing and field problems experienced by users of unsealed switches are caused by contamination of the internal switch contacts during soldering and cleaning processes.
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