Back when I was in high school, passing all of your classes each semester was sufficient for you to proceed to the next grade level. Of course, this included taking and passing a comprehensive and lengthy final exam. Today, students must still meet these individual course requirements; however, in most cases, they also have to take and pass standardized tests in Mathematics, Science, English, and Social Studies each year to move on to the next grade. The reasoning behind this stipulation, which was once federally mandated, is to ensure that all students achieve a minimum level of competency in these core areas, thereby demonstrating that they are prepared for their next challenge.
As electronic circuit boards comprise most of the tools and machinery that we use in all aspects of our lives, it is not surprising that there are many standards for PCB manufacturing. Even if you have never been in a board house, you are probably aware of the IPC classification system for PCB manufacturing where requirements are meant to ensure that differing performance objectives are satisfied. However, do you know the specific IPC standards for PCB assembly? Let’s take a look at these standards and discuss how you can ensure they are met.
What IPC Standards for Assembly Apply to My Design?
PCB development is neither a simple nor easy endeavor. Not only do you have to create a design that will achieve your performance goals, but you also have to create a manufacturing file package for your PCB that accurately conveys your design specifications to your CM. Once your design is created, the board has to be built. To achieve the best results, you should follow a plan or checklist to ensure your PCB quality. As your CM builds your boards, the manufacturing process must adhere to regulations and standards meant to ensure that your PCBs achieve acceptable levels of performance, quality, and reliability.
The prevailing source of guidelines and rules for much of the history of PCB design and manufacturing is the IPC Association Connecting Electronics Industries. In the figure below, an overview of these standards is presented .
Overview of IPC standards for PCBs
As illustrated above, the list of IPC standards for design (shown in green), fabrication (blue), and assembly (yellow) covers all aspects of PCB development. From the associated standards listed (shown in white), guidelines and rules for PCB assembly extend to many other standards. These additional standards target component types, assembly materials, soldering methods, testing, and repair. The importance of this last stage of PCB development is indicated by the number of IPC standards for PCB assembly there are.
How do I Ensure that My Boards Meet the IPC Standards for Assembly?
Typically, the restrictions, constraints, and tolerances for assembly, as well as fabrication, are determined by whether your board can be classified as an IPC class 1, class 2, or class 3. Class 1 is the least restrictive and used for commonly-used PCBs that are not required to last very long. Class 2 boards are typically found in computers and communications products. These boards are more stringently regulated as reliable performance is desired but not critical. Class 3 is the most tightly regulated and reserved for PCBs that are a part of systems where failure may be catastrophic. These include medical devices, such as life support, or aerospace vehicles.
To ensure that your boards adhere to the IPC standards for PCB assembly, you should be generally familiar with them and do the following:
A. Partner with a qualified, IPC certified CM
Although selecting a CM has been traditionally relegated to post design, it is far better for your PCB development process that you do so as early as possible. By selecting the best assembly CM during or at the start of design, you can incorporate choices and make decisions that will aid the assembly process and likely prevent delays and additional runs and costs.
B. Select the best IPC classification for your design
There may be times when it is better to opt for IPC class 2 instead of class 3 even though your board may be intended for critical industry usage; for example, if your board’s failure will not hamper the overall system’s ability to perform critical functions. If this choice can be made, it will simplify the manufacture of your boards. Your CM can help you make the best decision for your design.
C. Employ DFM specifications that meet or exceed your board’s IPC classification requirements
For the best development results, your design should be guided by your CM’s equipment and process tolerances or DFM rules. And the best DFM includes design for assembly (DFA) for optimal manufacturing. However, these must adhere to the IPC classification for your board.
Ensuring that the manufacture of your boards adheres to the IPC standards for PCB assembly involves more than just choosing whether your board is class 1, class 2, or class 3. The best way to ensure that these standards are met is to follow the keys for good PCBA design, which include forming an early relationship with a qualified CM.
|Tempo‘s Custom PCB Manufacturing Service
We will work with you staring on day one of design to ensure that your boards meet IPC standards. 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 Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.
 “IPC Standards: What Every Manufacturer Should Know.” Association Connecting Electronics Industries. Accessed May 23, 2019. https://www.ipc.org/4.0_Knowledge/4.1_Standards/OEM-Standards/IPC-OEM-Stds-A4-English-1111-ONLINE.pdf.