![]() ☐ Follow good design guidelines for footprints (as described in the video below).Įxample footprint design with Allegro PCB Editor.īy following the tips listed above, and instituting all DFM rules and guidelines, you can best assist your CM in making sure that your development does not suffer from any reflow-induced failures. ☐Make good use of thermal paste and other heat transfer techniques, if needed. ☐ Make sure there is adequate spacing between board elements. ☐ Select high-quality components without vulnerabilities to reflow temperatures. ☐ Ensure PCB trace routes connected to components are similar in size. Yet, by instituting a design-to-value approach, that includes making decisions that aid your CM in the assembly of your boards, as shown below, these manufacturability contingencies can be largely mitigated. In many cases, reflow-induced failure means that unusable boards are being manufactured, which can translate into longer turnaround times and increased manufacturing costs. Design Guidelines to Prevent Reflow-Induced Failure Fortunately, these can be avoided, as we discuss below. Head in pillow - may occur with excessive soak temperature or interval.Ĭomponent cracks - caused by a heating rate that is too fast.īoard warping or breaking - due to pressure applied after board weakening during reflow.Īs listed, the above contingencies occur as a result of imprecise reflow soldering execution however, there are design factors that contribute to the board’s susceptibility to these failures. Solder balls and/or beads - can result from insufficient heat. Oxide creation - can occur when oxygen is present during reflow. These and other contingencies are listed below. ![]() Possible issues range from poor solder joint quality to component and/or board damage. Potential Failures When Soldering SMDsĪlthough the through-hole soldering process can have challenges, these pale in comparison to the reflow-induced failure possibilities. Not adhering to the proper temperatures or time intervals can lead to failures, as discussed below. This is also true during the reflow stage as the temperature should be at or above the desired peak temperature for a fixed preset duration. ![]() It should also be noted that the temperature for the dry-out or soaking stage is ideally fairly constant. The temperatures shown for the reflow profile above are typical for the solder pastes in use most often by PCB contract manufacturers (CMs), with the peak for leaded solder at approximately 210-220☌ and lead-free solder about 30☌ higher. IMG: IR-reflow-temperature-profile.png in Cadence | Software Images | PCB Manufacturing | Assembly. (Alt text: A graph of the reflow soldering stages) The reflow stage of circuit board assembly is a thermodynamic process where the board is subjected to a range of temperatures over four intervals, as shown in the figure from below. Preset based on parameters that include: board size, number of components, number ofĪs stated above, reflow soldering is used to secure SMDs to the circuit board during assembly. The temperatures and time intervals for the stages are Involves running the board through an oven where it goes through a four-stage profile: To a PCB’s top layer, and for two-sided boards, the bottom layer as well. Reflow soldering is a surface mount technology (SMT) process for attaching components Let’s first define reflow soldering and then investigate how to best design boards to avoid potential reflow-induced failures that can threaten successful PCBA development. For surface mount components, along with pick and place, reflow is the most important stage. The design embodiment is finalized with the utilization of PCB assembly equipment to place and securely attach components. The process begins with and depends upon a well-defined design that includes specifying all materials, components, and their arrangement, or the stackup and PCB layout. PCBA development is a good example of how these four aspects of product generation are implemented. However, the quality of the result is often determined by the specific equipment and how effectively it is utilized. Armed with these essentials, virtually anything can be accomplished or produced. And, finally, you need the time to integrate the previous three. Third, is possessing the necessary tools or equipment. Second, is the knowledge or expertise necessary to execute the plan. To generate any tangible item of any degree of complexity, there are four essential requirements: First, is a clear plan or strategy. How to design your PCBA to prevent failures during reflow. What types of reflow-induced failure can occur during assembly?
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