The core concept of printed circuit board assembly DFM
1.PCBA manufacturability design procedure
The core concept of the printed circuit board assembly DFM is that before the printed circuit board layout, wiring design and pad design, the circuit designers and technicians of the product must master and comply with the PCBA manufacturability design procedure. The PCBA manufacturability design process is a prerequisite for implementing product manufacturability design.
Determining the design process - determining the overall function of the function, performance index and overall dimensions of the electronic product - the electrical principle and the mechanical structure design - determining the size and structural shape of the printed circuit board according to the structure of the whole machine - according to the function and performance of the product Indicators and product grades select printed circuit board materials and electronic components. A process plan is completed. The assembly process design is completed. Finally, the printed circuit board circuit design is performed. If you do not follow the above procedures, do not know the process plan and complete the assembly process design to start PCB design, then poor PCBA manufacturability is inevitable.
Determining the process plan and completing the assembly process design must be carried out during the overall design of the product, that is, in the overall project demonstration of each project and product, the process plan is proposed by the process master, and the total design of the circuit design master The division and crafts chief completed this work in the report of the program demonstration as an irreplaceable compulsory item for product program review! This is an important work that we must do in the product design phase of the product.
In the product plan demonstration, the chief craftsman and the electrical equipment technician participate in the whole program demonstration of the product, and propose the process plan and quality assurance outline according to the tactical technical indicators of the product: introduce the latest achievements of the electronic assembly technology at home and abroad to the circuit designer. Propose the electronic assembly process requirements in circuit design and the best electronic assembly process plan to ensure product tactical technical indicators: propose the pilot project to implement the electronic assembly process plan, the implementation route, and the equipment and infrastructure to be added And the characteristics of the electronic assembly that should be noted for this product. This is the first prerequisite for the design of product manufacturability.
The process work in the planning stage is the core and top priority of the whole process! Take PCB/PCBA as an example: in the first stage, according to the tactical technical indicators of the product, the use environment of the product and the installation density, etc. The assembly method determines the welding process form by the assembly method, and on this basis, according to the product characteristics, a set of PCB layout design requirements and pad design requirements suitable for the welding process are combed out from the mature working specification 2. The circuit designer serves as the basis for designing the PCB. At the same time, according to the requirements of the use environment of the product, installation density and reliability requirements, analysis of high-density components and micro-miniature components that may be selected, and the pilot project to implement the electronic assembly process plan and implementation Pathways, equipment and infrastructure that need to be added, and the characteristics of the electronic assembly that should be noted in this production.
The electrical equipment technologist participates in all product demonstrations is the first prerequisite for the implementation of product manufacturability design. At present, the quality problems of many electronic products are basically due to the lack of planning in the early stage! From the back end of the product design and manufacturing chain, everything has been “made a boat”, and it is too late.
2. The timing of the assembly process design
DFM can be divided into four phases by time, namely:
Basic Pre-Release Analysis
Strictly speaking, this is the true sense of manufacturability design DFM; Throughout the design process, in the early stages of the design cycle, start with the design to comprehensive analysis of design, cost, quality requirements, to find the most reasonable design balance.
According to the product's tactical technical indicators, product use environment and installation density requirements, the possible assembly method is proposed, and the welding process form is determined by the assembly method. Based on this, the product characteristics are sorted out from the mature process specifications. PCB layout design requirements and pad design requirements for this soldering process.
Analysis before trial production
Mainly check the design content before trial production, check the rationality of product design from DFM, DFA, DFT and design documents; most of our current electronic enterprise applications, including the use of DFM software and manual manufacturability or process analysis, it is a pre-trial analysis.
Analysis after trial production
The quality analysis after the trial production of the product mainly refers to the feedback after the trial production. The problems found in the trial production are summarized and to the designer, so as to update the design and improve the manufacturability of the product within the feasible scope, but after all, it is already repaired. The impact of different stages of implementation on product design and production costs is also different. The earlier the stage of DFM participation, the easier it is to solve the problem and the smaller the loss.