PCB Tech - Discussion on component placement in high density PCB design

When printed circuit boards replaced the slow and cumbersome manual strips and systems of the past, it became a novel technology that enabled electronics engineers to assemble complex electronic systems relatively quickly, easily and inexpensibly. As a result, the electronics industry has made great efforts to make the manufacture of these plates as easy as possible. A lot of money has been invested and used to design software to help design, manufacture, assemble, inspect and test printed circuit boards.

These technologies enable design engineers in the electronics business to invest in improved processes that reduce the size of parts, produce surface mount (SM) and ball grid array (BGA) packages, and reduce the line width and size of PCB. Other features, use X-ray imager for better card inspection, etc.

The slow introduction of artificial intelligence (AI) into design software means that some key tasks, such as the placement of PCB components, are still manually controlled by layout engineers. As a design engineer, you will need to ensure an understanding of part placement to ensure design stability.

Evolution of component placement throughout the design career

I designed a low density, sexual circuit board using a winding method. Then there's the opportunity to make printed circuit boards. I started with simple PCBS (through hole parts, reasonably sparse design) to simple and even large SMT parts. This meant that the manual welding process that followed the PCB design process was fairly simple in the early days.

However, the further you go in your career, you are assigned to use high-density PCBS in order to manufacture tiny SMT, BGA, and QFN parts in fragile design environments, and to use thin lines and small spacing between components in the layout. This makes "assembling" PCBS a new variable that design engineers must deal with. This may come as an unpleasant surprise to some, but I believe in forewarning.

Place the parts on the PCB

A PCB can be assembled in one of many different ways. Design engineers should consider specific assembly techniques such as machine assembly, manual assembly, and hybrid assembly (manual and infrared ovens) before embarking on PCB design. These choices often depend on cost, time, quantity, and the type of design the engineer is con

sidering.

Many considerations drive the process of placing parts on the PCB. Signal length (small sum), ease of assembly, and ease of testing are all critical to PCB assembly. Below, we'll explore the unique components that assemble each aspect.

Important guidelines for conference types and DFA

In the electronics industry as a whole, you will almost certainly be dealing with many different kinds of assembly. It is important to familiarize yourself with what is involved in each process, the advantages and typical uses of each assembly form, and how well the DFA process can be optimized to match the final PCB production.

Placement of PCB components in machine assembly

It can often be assembled by machine and used for mass production. The footprint of components on the PCB must be, and must comply with all design rules. Machine assembly does not provide any flexibility that can be achieved by using people in the loop to manufacture the PCB.

The machine assembles the card yes. It uses expensive industrial machines to design and assemble PCBS according to the rules. The need for non-repetitive engineering time means that this method is usually reserved for high-volume welding.

Examples of violations of design rules that may be rejected by an automated system (machine assembly)

Manual assembly and welding of bridge problems

Manual assembly is a slow technique. This is time consuming and requires full-time human work. It is also prone to error. Short circuits caused by welding Bridges have ruined many engineers' careers. As a result, most agencies work with two technicians - the assembler and the quality assurance (QA) technician, who check the assembler's work to ensure that the solder bridge on the PCB does not grow.

The assembly technician must be a very talented person. They put you in violation of design rules not allowed by machines or even hybrid assemblers. Therefore, if the design (typically a small batch design) violates the design rules to achieve compactness, then manual welding is the way to go.

Mix components in infrared oven or wave soldering

The rest of the market is occupied by hybrid assembly methods, in which technicians place components on cards and complete the welding process using IR ovens or wave welders.

Hybrid components typically use templates and solder paste to create solder-coated PCBS, where the assembly technician simply places the part on the designated footprint and then places the filled card in the oven to complete the reflow/weld process. If errors such as vertical lift occur during oven welding, the mixers must leave enough space between parts to place them manually and rework the weld cards. Quality control technicians may also be part of the production line.

Component placement in high-density PCB design

The need to make high-density PCBS creates new temptations that are not present in sparse designs. When engaged in high-density design activities, it is important to remember that even in high-density systems, old design methods must be followed.

One of the common practices that designers refuse to follow is to discard reference code, which leads to a significant increase in density. However, the assembler still needs this information to assemble the card. The removal of these indicators means that the engineer is now responsible for creating additional documentation to assist and guide the assembly technician during the PCB assembly process.

Remember - A PCB, such as a schematic or program, can take a lot of effort to go through the development process before it becomes a reality, so each step must include enough documentation to allow others to interact with your creation. Always think about how your design choices will be perceived by the people who interact with your design after you.

All of us believe that the next person might not pay the high price for your gadget. Someone on the design and assembly team may have to convert your PCB to a fully operational electronic system to make your dreams a reality.