At present, for lead-free soldering materials and lead-free soldering process of information has a lot of, for the need to develop lead-free welding process factory, correct choice these information and their organic combination is very important. To development a sound, high qualified product rate of lead-free welding production line, need to be carefully planned, and for the implementation of the plan to make efforts and strict process monitoring to ensure the quality of the product and the process in a controlled state. These controls are associated with a number of changes, such as materials, equipment, compatibility issues, pollution issues, and statistical process control (SPC) procedures.
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Lead free welding materials, the welding process will have a serious impact. Therefore, in the development of lead-free welding process, the welding process must be optimized for all relevant aspects. Westby Georze on the development of lead-free soldering process five steps to help lead free welding process development and process optimization.
1 select the appropriate materials and methods
In lead-free soldering process, the choice of welding material is the most challenging. Because for lead-free soldering process, lead-free solder, solder paste, flux, and so on material selection is the key, is also the most difficult. In choosing the material, the type of the welding element, the type of the circuit board, and the condition of the surface coating are also considered. Selection of these materials should be in their own research to prove, or the authority or the literature recommended, or the use of experience. These materials are listed in the table to be tested in the process experiment, so that they are deeply studied and the influence of them on all aspects of the process is understood.
For welding methods, according to their own actual situation to choose, such as component types: surface mount components, through hole inserted components; circuit board situation; plate on the number of components and distribution. For welding of surface mounting components, the reflow soldering method; for through-hole components, according to choose wave soldering, dip or spray welding to weld. Wave soldering is more suitable for the whole board (large) through hole plug-in components welding; dip is more suitable for in the whole board (small) or in local area through hole plug-in components welding; spray flux is more suitable for on board on individual components or a through hole plug-in components of welding. In addition, but also pay attention to is that lead-free soldering the whole process than the leaded solder to long, and the required welding temperature is higher. This is due to the melting point lead-free solder is higher than the lead in solder, and its infiltration and also because of some difference.
After the welding method is selected, the type of welding process is determined. At this time, according to the welding process requirements of the selection of equipment and related process control and process inspection equipment, or to upgrade. The selection of welding equipment and related equipment is the same as the choice of welding material.
2 to 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. Process route and process conditions are determined through experiments. In the experiment, a full test is needed to understand the characteristics and the influence of the welding material on the list. The aim of this step is to develop lead-free solder samples.
3 develop and perfect welding process
This step is the second step to continue. It is the second step in the process of testing data collected to analyze, and then improve the materials, equipment or change process, in order to obtain a sound process under the conditions of the laboratory. In this step also to clarify the lead-free alloy welding process may produce contamination know how to prevent and determine the welding characteristics of the process capability (CPK) value, and compared with the original tin / lead process. Through these studies, we can develop the welding process inspection and testing procedures, but also to find out some of the process of out of control processing methods.
4 also need to test the welding samples, in order to determine whether the quality of the product meets the requirements. If you fail to meet the requirements, you need to find out the reasons and solve it until you reach the requirements. As soon as the welding product can be reached to the requirements, lead-free soldering process development is successful, the process for the production of a quasi ready to prepare the operation
Everything is ready, now can be changed from sample production to industrial production. At this time, the process is still needed to be monitored to maintain the process in a controlled state.
5 control and improvement process
Lead free soldering process is a dynamic stage. The factory must be alert to various problems that may arise in order to avoid process control, but also need to continue to improve the process, in order to make the product quality and the quality of the qualified rate has been improved. For any lead-free soldering process, improve the welding materials, as well as the update of the equipment can improve the product's welding performance.