pcb manufacturing
As a PCB designer, you need to consider the production and assembly process before you start your design. This will help to reduce costs and prevent any unforeseen issues during manufacturing and assembly. Some of these issues are easily recognizable and can be avoided with careful planning, but others may be difficult to see and can have major effects on the final product’s functionality. Some of these issues are related to component placement, which will be discussed below, while others are more involved and have to do with the overall layout of the board itself.
The first step in the pcb manufacturing assembly process is component placement. After a detailed blueprint has been created, automated pick and place machines will delicately arrange all of the components on the bare board. This is done by a combination of high-precision robotic arms and vacuum nozzles. The precise positioning of each component ensures that it is connected properly and that all connections are complete. The next phase in the production process is soldering. During this stage, a metal alloy known as solder is heated to a molten state, creating a robust electrical and mechanical bond between the components and the bare board. There are a number of soldering methods that can be used in the assembly process, including selective, wave, and reflow.
The choice of these methods will ultimately dictate the final cost of a PCB. For instance, if your design requires a large number of through-hole connections, the assembly will be more expensive than using surface mount technology. Also, if the assembly will need to undergo any testing procedures (ICT, flying probe, AOI, and X-ray), you should plan for these costs as well.
What are the design considerations for pcb manufacturing assembly?
In order to minimize assembly and manufacturing costs, it is important that your design uses minimal component sizes. For example, using an 0805 sized capacitor or resistor rather than a 1206 size cap can free up significant space on the circuit board. In addition, it is a good idea to use multiple vias at all layer transitions to increase reliability and improve thermal conductivity. Finally, be sure to leave enough space around components that emit heat to avoid any issues with melted solder or hot spots.
One of the biggest issues that can arise during assembly is the failure to include pin 1 indicators and component polarity/orientation markings on the silkscreen. This problem occurs in more than 75% of all orders my facility receives, and it can lead to serious production delays.
Another common assembly issue is the inclusion of unnecessary features. For example, excessively thick traces will be hard for the machines to handle during component placement, and they can cause signal degradation. Similarly, excessively large pads can prevent the correct alignment of the components during soldering. The pads on a PCB should be commensurate in size to their mates; otherwise, tombstoning will occur. Incorrectly aligned pads can result in short-circuiting, a problem known as “the great divide”.