PCB Fabrication

Five steps to complete the lead-free soldering process

by:A-TECH      2021-03-29
Nowadays, most of the lead-free soldering materials that have more or less influence on the soldering process are used. Therefore, we need to optimize the soldering process. The five-step method proposed by Georze Westby is used to develop the lead-free soldering process. And process optimization.   First of all, we have to choose the appropriate materials and methods.    In the lead-free soldering process, the selection of soldering materials is the most challenging. Because for the lead-free soldering process, the selection of lead-free solder, solder paste, flux and other materials is the most critical and the most difficult. When selecting these materials, the types of soldering components, the types of circuit boards, and their surface coating conditions must also be considered. The selected materials should be proven in their own research, or recommended by an authority or literature, or have experience in use. List these materials in a table for testing in the process test, so as to conduct in-depth research on them and understand their impact on all aspects of the process.   For the welding method, you should choose according to your actual situation, such as component types: surface-mounted components, through-hole plug-in components; the situation of circuit boards; the number and distribution of components on the board. For the soldering of surface-mounted components, reflow soldering is required; for through-hole plug-in components, wave soldering, dip soldering or spray soldering can be selected for soldering according to the situation. Wave soldering is more suitable for the soldering of through-hole plug-in components on the entire board (large); dip soldering is more suitable for soldering through-hole plug-in components on the entire board (small) or in a local area of u200bu200bthe board; local spray flux is more suitable Soldering of individual components or a small number of through-hole plug-in components on the board. In addition, it should be noted that the entire process of lead-free soldering is longer than that of lead-containing solder, and the required soldering temperature is higher. This is because the melting point of lead-free solder is higher than that of lead-containing solder, and its infiltration The sex is worse.   After the welding method is selected, the type of welding process is determined. At this time, it is necessary to select equipment and related process control and process inspection instruments or upgrade them according to the welding process requirements. The selection of welding equipment and related instruments is the same as the selection of welding materials, and it is also quite critical.  Secondly, we will determine the process route and process conditions. After the first step is completed, the welding process test can be carried out on the selected welding materials. Determine the process route and process conditions through experiments. In the test, it is necessary to conduct sufficient tests on the welding materials selected in the list to understand their characteristics and influence on the process. The purpose of this step is to develop samples for lead-free soldering.   Again, the development of a sound welding process is also indispensable  This step is the continuation of the second step. It is to analyze the test data collected in the process test in the second step, and then improve the materials, equipment or change the process in order to obtain a sound process under laboratory conditions. In this step, it is necessary to clarify the possible contamination of the lead-free alloy soldering process, know how to prevent, measure the process capability (CPK) value of various soldering characteristics, and compare with the original tin/lead process. Through these studies, inspection and test procedures for welding processes can be developed, and at the same time, some treatment methods for out-of-control processes can be found.  Fourth, we also need to conduct reliability tests on the welding samples to identify whether the quality of the product meets the requirements.    If it does not meet the requirements, we need to find out the reasons and solve them until the requirements are met. Once the reliability of the soldering product meets the requirements, the development of the lead-free soldering process will be successful. This process is ready for mass production. After the operation is ready, everything is ready, and now it can be transformed from sample production to industrial production. At this time, the process still needs to be monitored to maintain the process in a controlled state.   Fifth control and improvement process   Wu-lead soldering process is a dynamically changing stage. The factory must be alert to various problems that may arise to avoid out-of-control scenarios. Of course, it must also improve the level of process production so that the quality can be improved.
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