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The last thing an OEM wants is for his boards, supposedly populated with eutectic components, to go through the lead-free reflow oven and come out damaged. The OEM seeking lead-free design, fabrication, and assembly must cast a wary eye on the system an EMS provider has for separating eutectic versus lead-free components and assuring timely and efficient lead-free board design and fabrication.
Reflow profile should be performed by attaching calibrated thermal couples embedded in the spheres of the larger BGA parts and other critical PCB locations to ensure all components are heated to temperatures above minimum reflow temperatures and that smaller components do not exceed maximum temperature limits. Maximum reflow temperature is in the 245✬ to 260✬ range, depending on complexity and density of the board. The lead-free alloy used for BGA solder balls has a melting point of 217✬ and requires a minimum reflow temperature of 235✬ to ensure good wetting. The lower temperature limit for reflow is usually 200✬ and upper limit is about 235✬. The melting point of the eutectic solder is 183✬. The reflow process window for conventional soldering is relatively wide. During stencil design, it’s important to keep in mind that lead-free pastes have higher surface tension and do not wet or spread on the surface of pads as easily as eutectic solder pastes. Paste manufacturer recommendations should be carefully followed to avoid issues. Lead-free solder paste shelf life differs from the traditional eutectic solder paste. The one selected should be non-hazardous, mechanically reliable, thermal fatigue resistant, good wetting, relatively low melting temperature and must be compatible with a variety of lead-bearing and lead-free surface coatings. A wide range of lead-free solder paste alloys are available. PCB surface finishes must be able to withstand reflow temperatures without incurring warpage or other surface damage. Several important factors must be considered for lead-free soldering. That’s because the material set used for lead-free soldering is different and higher reflow temperatures are required. However, there are some important differences that must be taken into account for lead-free soldering. The similar equipment and process steps are often used for both. We strive to produce the highest quality PCBs and assemblies to meet all our customer needs.The reflow soldering process for lead-free components is similar to conventional eutectic solder reflow process. These low peak temperatures allow for soldering of thermally sensitive assemblies.įor all your sensitive electronic assembly needs, including specialized processing such as low temperature applications, please send us your project requirements now, either through our online quote tool, or to. The SnBiAg alloy system has a melting point of 138☌ which enables a peak reflow temperature between 160 - 170☌. #Solder reflow temperature free#
Lead free solders like Tin / indium 52% and tin / bismuth 58% have significantly lower melting points than tin / lead 37% solder. Two metals help to reduce the melting point, indium, and bismuth. Tin/bismuth, tin/indium, or tin/bismuth/silver are the most common “low melting point” solders (150-170° C). Solders generally melt between 90° C and 450° C.The melting point of solder is engineered via selection of the solder blend and the heat resistance power of the particular devices being attached.
By using two different reflow temperature pasts, the parts attached in the first step with a higher temperature paste, can be unaffected by the second lower temperature application. That is, some may require components to be attached first, and then additional ones added in a second step. Low temperature pastes can also be used in conjunction with higher temperature ones for applications requiring two-stage assembly.
Low-temperature solder pastes that melt at a heat below 180° C are used for such situations, as “typical” pasts generally reflow at 250° C or higher. The exact solder paste reflow temperature is essential to ensure certain components do not excess their maximum temperature rating during assembly. Size, composition, and flux density play significant roles determining the effectiveness of manufacturing process. The purpose of solder paste is to create a stable bond between the plated connection pads on the PCB board and the electronic components being added to form a working electrical circuit. Solder paste is a combination of small metal solder particles and flux used in printed circuit board assembly & manufacturing.
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