Surface assembly quality inspection is a very important link in SMT production. It is a description of the degree to which the inherent characteristics involved in the assembly process and results of surface assembly products meet the requirements. The inspection process runs through the entire SMT production process. The basic content of SMT inspection includes three categories: incoming material inspection before assembly, process inspection during assembly, and component inspection after assembly. There are basically three standards based on whether the test results are qualified, that is, the enterprise standards designated by the unit, other standards (such as IPC standards or SJ/T 10670-1995 general technical requirements for surface assembly processes), and special standards for special products. At present, my country usually adopts IPC standards to inspect products.
Incoming material inspection before assembly is not only the basis for ensuring the quality of the SMT assembly process, but also the basis for ensuring the reliability of SMA products. Only qualified raw materials can have qualified products. Therefore, incoming material inspection before assembly is an important part of ensuring the reliability of SMA. . With the continuous development of SMT and the continuous improvement of the requirements for SMA assembly density, performance, and reliability, as well as the further miniaturization of components and the acceleration of the application and update of process materials, the quality of SMA products and their assembly has an impact on the quality of assembly materials. Sensitivity and dependence are increasing, and incoming inspection before assembly becomes an increasingly important link. The selection of scientific and applicable standards and methods for incoming material inspection before assembly has become one of the main contents of SMT assembly quality inspection.
The main content of SMT patch detection technology
1. The main content and testing methods of incoming material inspection before assembly
The incoming materials before SMT assembly mainly include components, PCB, solder paste, flux and other assembly process materials. The basic content of the inspection includes the solderability of components, pin coplanarity, performance, PCB size and appearance, solder mask quality, warpage and distortion, solderability, solder mask integrity, solder paste Metal percentage, viscosity, average amount of powder oxidation, metal contamination of solder, activity and concentration of flux, viscosity of bonding agent, etc. Corresponding to different inspection items, there are many inspection methods. For example, there are many methods such as immersion test, solder ball method test, and wetting balance test for solderability test of components.
2. Incoming material inspection standards before assembly
The specific items and methods of SMT assembly incoming inspection are generally determined by the assembly company or product company according to product quality requirements and related standards. The relevant standards that can be followed have begun to be gradually improved.
For example, the standard IPC-AT10D "Acceptability of Electronic Components" formulated by the American Electronic Circuit Interconnection and Packaging Association (IPC), China Electronics Industry Standard SJ/T 10670-1995 (General Technical Requirements for Surface Assembly Processes", SJ/T 11186 -1998 "General Specification for Tin-Lead Paste Solder", SJ/T 10669-1995 (General Specification for Solderability of Surface Mounted Components", SJ/T 11187-1998 "General Specification for Adhesives for Surface Mounting", national standard GB 4677. 22-1988 (Test Methods for Ion Contamination on the Surface of Printed Boards", American Standard MIL-I-46058C "Insulating Coatings for Coating Printed Circuit Components", etc., all have corresponding requirements and specifications for SMT assembly incoming inspection. SMT assembly companies According to product customers and product quality requirements, based on the above-mentioned related standards, combined with the characteristics and actual conditions of the company, for specific product objects and specific assembly incoming materials, determine related testing items and methods, and form standardized quality management procedures and documents , Strictly implemented in the quality management process. Table 6-2 is an inspection specification for incoming materials such as surface mount resistors formulated by a company for specific product objects and quality requirements. It specifies the inspection items, standards, methods and content in detail Wait.