Handle Component Lead Trimming in PCB Assembly and Manufacturing
Printed circuit board (PCB) assembly and manufacturing requires precise techniques to ensure reliable connections between components. A single error can disrupt the function and integrity of a finished product, so it is important to understand common issues in order to avoid them. By carefully following step-by-step guidelines for pcb assembly and manufacturing component placement, manufacturers can ensure precision installations and meet stringent quality standards.
Through-hole technology, or THT, works well for larger components with leads or wires that need to be plugged through holes on the PCB. It involves a manual or automated process, depending on the type of equipment used. For smaller surface mount components, or SMDs, robotic pick and place equipment adds the parts to the PCB. In both cases, the first step of the process is to apply solder paste and silkscreen the board with a pattern of apertures that matches the size of the component’s lead. Once the paste is applied, the board is sent on a conveyor belt to the robotic pick and place equipment to automatically select, deposit, and position the SMDs.
After SMDs are deposited, a thin layer of copper is added to the pads where the components are inserted and soldered. This copper layer acts as an electrical conductor and carries signals from the components to the inner layers of the PCB. These signals carry information, such as sound or video, from the components to the circuits they control.
How to Handle Component Lead Trimming in PCB Assembly and Manufacturing
A bare PCB is sometimes called a circuit board or a circuit card, and it is the core of most electronic devices. The copper on the bare PCB is a layer of either etched copper or a full-on copper coating. During fabrication, the copper layer is often patterned with “drill hits” where the drill will create holes on the substrate for insertion of through-hole components. These “holes” or vias connect to the inner layer traces and pads.
Once the pads and traces are properly positioned, it’s time to add the through-hole (PTH) components. The first step in the PTH assembly process is to align the component leads with the corresponding holes on the PCB and insert them. Once inserted, the next step is to apply flux to promote solder flow and to provide mechanical adhesion between the component and the pad. Finally, the components are heated with a soldering iron to melt and seal the solder joints.
One of the most common assembly issues is known as solder bridging, which occurs when unintended connections form between adjacent copper features. This can cause intermittent or even outright failures during reflow soldering. This is caused by insufficient solder paste deposition, poor alignment of the component to the pad, or a combination of these factors. Insufficient solder paste can also contribute to lifted pads, a condition that can cause thermal stress and damage the PCB during reflow soldering. The best way to prevent these problems is by compiling a comprehensive bill of materials that includes reference designators, ratings, and quantities to guide procurement and ensure proper inventory management.
