When we look over our history, it is truly amazing to learn about some of the feats humans have achieved. A prime example of this is the series of churches built in Lalibela, Ethiopia. Probably, the most famous is the Bete Giyorgis. These structures are astounding, not only because they are built into instead of upon the ground, but also because they are monolithic or formed of a single solid rock. This style of building makes the structures reliably strong and durable. These are qualities that are sought after in virtually all areas of construction.
Having a PCB that it is able to withstand any electrical, mechanical, or structural adversity throughout its expected lifetime is certainly an objective of the board construction process. These goals are shared equally by board fabrication and PCB assembly. For fabrication, the threats are cracking and breakage, while for assembly, the threats are opens or shorts that can damage components and the board. These threats can be mitigated or even eliminated by an optimal electronic PCB assembly process. And what is optimal electronic PCB assembly? Let’s answer that question first and then define a means of ensuring its implementation.
What is Optimal Electronic PCB Assembly?
Printed circuit board assembly or PCBA accounts for roughly half of the steps in the manufacturing stage of PCB development. Virtually all of these are focused on preparing your boards for component mounting, actually mounting the components, or ensuring the components are securely mounted. Following these steps satisfy the general requirements for attaching your surface mount technology (SMT) or through-hole components, in most cases. However, following these steps does not guarantee that your board’s manufacture will meet your quality, reliability, or speed objectives.
All board designs, except for the simplest of circuits, typically have constraints, restrictions, or special criteria to which your PCB development must adhere. These may include or fall under one of the following:
- Delivery schedule limitations
One of the most important aspects for many designers is the manufacturing turnaround time. The ability of a CM to build boards quickly significantly affects development cycle time.
- Operational lifecycle
If your design is for a critical system, such as class 3 medical devices, then reliability is at a premium, as system failure may result in misdiagnosis or even loss of life.
- Component restrictions
Many industries and original equipment manufacturers (OEMs) have strict requirements for the components that can be used in their systems. For example, suppliers of the military and aerospace industry require that supply chains be documented to avoid counterfeit components.
- Acceptance quality level (AQL) limits
Quality should always be a priority as it can impact your production levels and return on investment (ROI). However, some clients have higher standards, which may be required due to environmental or extended deployment concerns.
- Manufacturability level
Depending on the system your board will be a part of, there are various manufacturing levels of acceptable performance. To satisfy the highest of these IPC-6011 defined levels for PCBs, there are assembly requirements to minimize defects and ensure a high level of performance can be relied upon by end-users.
- Yield rate targets
Another important metric that directly affects product development costs is the yield rate, which is the ratio of usable boards to boards actually built. Maximizing this rate is or should be a production goal for every design, as it plays a major role in determining your profit margin.
- Testing requirements
The only means of gauging your board’s ability to meet its intended objectives is by testing. This testing may be to evaluate the design via design testing or assess the board’s physical properties with manufacturing testing.
- Regulations and standards
All circuit boards are subject to regulatory control. Minimally, there are standards for board construction and materials. There are also quality management and risk mitigation standards if your PCB will be used in sensitive or critical systems, such as medical devices and aerospace systems.
As electronic PCB assembly is the final stage of board manufacturing, it assumes the role of verification that your board satisfies all applicable criteria, such as those listed above. Therefore, optimal electronic PCB assembly is defined not only by the process of securely attaching your components but also by the ability to identify deficiencies in design and fabrication which make achieving good, secure connections difficult or impossible.
How Do You Ensure Optimal Electronic PCB Assembly?
Functionally, electronic PCB assembly is performed by your contract manufacturer (CM). However, your CM is limited by the data and information that you provide. Therefore, your design decisions play a critical role in the assembly process. Following the suggestions below will go a long way toward aiding your CM to achieve the best possible electronic PCB assembly for your design.
Suggestions for Optimal Electronic PCB Assembly
- Make good component choices - Procure components from reliable sources and plan for possible shortages.
- Make sure your design package is accurate and complete - The best rule of thumb is clarity is better when it comes to design data. This includes not just materials, layout, and stackup, but also images, descriptions, and any special considerations.
- Ensure that your BOM matches your layout - Double check to avoid mismatches between component footprints and your BOM component packages. Otherwise, you may face delays and extended turnaround times for your boards.
- Utilize SMT and avoid through-hole components, if possible - Soldering surface mount devices (SMDs) and through-hole components are different processes; therefore, it takes longer to do both and much longer when many of the components are through-hole.
- Use single-sided component placement - Similar to using different soldering techniques, top and bottom mounting takes longer than single-sided mounting.
Follow design for assembly (DFA) guidelines - Applying DFA is critical for assembly optimization. Not doing so will likely cost you valuable time to make design corrections.
|Tempo‘s Custom PCB Manufacturing Service
Optimal electronic PCB assembly is somewhat case-specific, as each design has its own objectives. With this in mind, following the suggestions above can be broadly applied by tailoring them to your particular design. To help facilitate these, it is best that you select a qualified CM early in design. At Tempo Automation, we will partner with you on day one to provide support and ensure that you have the best PCB manufacturing experience and achieve the best results.
And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium user, you can simply add these files to your PCB design software.
If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on electronic PCB assembly or how to ensure that it is optimal for your design, contact us.