PCB Fabrication

PCB fabrication and assembly

Publish Date:2020-11-06

Up to 80% of the final product cost depends on how it is designed (the rest is usually paid for by management fees and capital costs). Of course, it is very important to reduce the product cost in design to produce a successful and cost-competitive final product. Manufacturing and assembly design is a formal method of checking the cost of product components and assembly, which aims to reduce costs before starting actual production. This paper will first discuss the manufacturing and design of the assembly concept in general, and then discuss in detail the PCB design related to manufacturing and assembly design in the following items. Finally, the last article concludes this series with the most common PCB design issues.
Before continuing to describe, it is necessary to discuss how the term “manufacturing design” is used in more general terms and more specifically in PCB manufacturing. In general, design for manufacturing and design of assembly can refer to the simplification and optimization of prototype or conceptual design to prepare for its manufacturing. When these terms are used to discuss PCBs, they usually mean examining potential manufacturing problems more directly. The first entry in this series will use the previous definition, as we discuss concepts in a broad sense, and the second and third will use the latter definition as we shift our focus to PCB manufacturing and assembly.

PCB fabrication and assembly


Overview of PCB fabrication and assembly design
In general, the purpose of discussing manufacturing and assembly design is to determine how to design products that can be manufactured and assemble them in the most cost-effective manner. Manufacturing design (DFM) involves reducing overall production costs, and more obviously, assembly design (DFA) involves reducing material inputs, indirect capital costs, and reducing labor. Both of them focus on the application of standards to reduce production costs and also seek to shorten the product development cycle. The combination of the two methods is often referred to as manufacturing and assembly design (DFMA). Two types of analysis will be discussed in the following sections, as they are closely related and the two terms are often used interchangeably.
The PCB design of general rule PCB fabrication and assembly conforms to
After the first conceptual design was created, DFMA analysis began. The conceptual design may involve creating prototypes or developing new versions of the product. After you create a conceptual design, you can check the bill of materials (BOM) for that design through DFMA analysis. DFMA adheres to the following rules:
Reducing the number of components in PCB design is a direct goal and has obvious advantages. It will reduce design costs and assembly complexity, although not obvious, but it has great benefits. For example, when picking and placing machines to fill PCB components, they are limited to the number of components they can support in a single pass. Note that picking up and placing the number of components used by the machine when assembling circuit boards can result in an insignificant cost reduction. For example, if the design requires a 20K resistor and a 10k resistor has been used in the design, it may actually be cheaper to use two 10K resistors in series, which can reduce the number of times the machine is picked up and placed. Similarly, looking for standard ICs that can integrate part of your design into a single IC can speed up assembly time and transfer some of the test requirements to the IC manufacturer. Therefore, paying attention to the number and type of PCB components may be the most important step to reduce the overall PCB production cost. In short, if the final design does not require parts, eliminating them will reduce BOM costs, procurement costs, processing time, test time, and assembly labor input.

Development of modular design

PCB fabrication and assembly


If these modules can be used in a variety of different products, consider splitting the PCB design into functional modules. Increasing the number of specific modules ordered from the manufacturer can significantly reduce the cost per unit of that module. It is also worth noting that using modules can reduce the cost and complexity of testing completed components by simplifying the testing process. Smaller systems themselves are easier to test and repair than larger systems. Obviously, the cost benefits you can get from modular design applications must be weighed against the increased interconnection costs associated with using multiple modules. Other advantages of modular design include ease of design updates, standardization of subsystems across multiple products, and simple troubleshooting of product subsystem design failures.
Strive to use standard components
Using standard components can greatly reduce the time and cost of design and development. There is no doubt that specifying a complex custom solution will greatly increase the upfront cost of any product and may make the design infeasible. Using more common components can also simplify production.
Product supply chain and reduce component supply problems. Another advantage of preferring standard components is that their footprints are easier to verify before they are used in PCB design.
Rely more on components

PCB fabrication and assembly


As long as electrical components have multiple uses in design, PCB designers should use them. For example, using an enclosure that can also be used as a radiator in a design can significantly save design costs. Another example of a dual-purpose device is to use support as a ground connection from the PCB to the PCB housing through the mounting holes connected on the PCB.
Design modules used in a variety of products
The use of standard parts in a range of products can reduce processing costs and achieve mass purchase costs. This concept can also be extended to product modules. If a module can be used for more than one product, higher production can reduce the cost of the module and ultimately the cost of the finished product.
Design easy to manufacture
Choosing PCB materials that need less processing in the manufacturing process can greatly simplify product manufacturing. Avoiding operation (e.g. the shell must be painted with the appropriate housing material) eliminates the entire manufacturing step and reduces the cost of the product. In addition, ensuring that design components do not produce excessive tolerances eliminates time-consuming and expensive part rework during assembly.
Reduce and avoid fasteners if possible
When PCB is to be assembled, as, with all products, it is more expensive to use fastener mounting components rather than press-fit mounting technology. To take advantage of this, try reducing the use of fasteners in assembly. One method is to use a surface-mount version of the power IC and integrate heat dissipation into the design of the circuit board. For example, switching from the TO-220 version of IC with an external heat sink to the D2Pak version using PCB as the integrated heat sink can save a lot of money in the final design.
minimize assembly orientation
If possible, install all parts along one shaft starting from the same side of the assembly. This is often referred to as a “top-down” component, where all components are installed from the top to the final component. The time required to rotate and rotate the product in the assembly process can be saved by using this single side assembly process. Therefore, as with all design decisions, PCB design engineers must weigh whether to better produce smaller PCBs with components placed on both sides of a circuit board, rather than designing a larger PCB, where the components are only placed on one side of the board (part has the ability to handle single-sided PCB assembly and double-sided PCB assembly).
· maximize component layout acceptance
Engineers should design PCB to reduce component installation errors. This can be achieved by using components with higher dimensional tolerances (higher pin spacing) or avoiding problems such as tombstones. The failure rate of components can be greatly reduced by using parts designed with high horizontal placement tolerance. In addition, using a rigid and predictable size infrastructure can also improve the rate at which components are placed correctly. In addition, machine vision type feedback systems and other forms of feedback enable placement automation processes to significantly increase production.
? minimize repositioning and handling during PCB assembly
Any time the PCB is repositioned during assembly increases the time required to assemble components on the PCB. It is easy to understand that as long as both sides of the PCB and components are installed on the front and back of the PCB, relocation will occur. If possible, use all surface mount components on one side of the board. The reflow soldering procedure may be used to limit the soldering steps of a single soldering component to the surface.
Advantages of PCB design for PCB fabrication and assembly
Fewer parts to be processed
It can reduce the cost of the bill of materials.
Treatment costs can be reduced to some extent.
Labor and energy input can
The overall manufacturing time can be shortened, thus greatly improving the manufacturing efficiency.
The lower the complexity, the higher the reliability.
The products can be more competitive.
Higher profits will be achieved.