PCBA Tech - Some detection technologies for SMT patches

Surface assembly quality inspection is a very important link in PCBA production. It is a description of the degree to which the inherent characteristics involved in the assembly process and results of the surface assembly product 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 this 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 SMT assembly process, but also the basis for guaranteeing 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, the acceleration of the application and update of process materials and other technological development trends, SMA products and their assembly quality have an impact on the quality of assembly materials. Sensitivity and dependence are increasing, and incoming material 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.

1. The main content and testing methods of incoming material inspection before assembly

The incoming materials before SMT assembly mainly include assembly process materials such as components, PCB, solder paste, and flux. 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, and 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 multiple methods such as immersion test, solder ball method test, and wetting balance test for solderability test of components.

2. Inspection standards for incoming materials before assembly

The specific items and methods of SMT assembly incoming material 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), the Chinese 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 Mount Components", SJ/T 11187-1998 "General Specification for Adhesives for Surface Mounting", national standard GB 4677. 22-1988 (Test Method for Ion Contamination on the Surface of Printed Boards", American Standard MIL-I-46058C "Insulation Coatings for Coating Printed Circuit Components", etc., all have corresponding requirements and specifications for PCB assembly incoming inspection. SMT assembly companies According to product customer and product quality requirements, based on the above-mentioned relevant standards, combined with the characteristics and actual conditions of the enterprise, for specific product objects and specific assembly materials, relevant inspection items and methods are determined, and standardized quality management procedures and documents are formed, 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.