Doing the laundry is a matter of dumping dirty clothes into the washing machine, pouring in detergent, and hitting start, right? Well, that’s what I thought until I ended up with shrunk clothes, stained shirts, and occasionally, pieces of tissue stuck to every garment.
The reality is, there is hidden know-how to doing the laundry, just as there are certain issues that you must pay attention to for your printed circuit board to be manufactured correctly. If you think that placing hundreds of parts and routing thousands of connections is the hard part and you can afford to be a little complacent in the manufacturing details, you would be wrong.
No matter how much you’ve perfected your design for its function, you still need to be aware of the different design details that could have an effect on the manufacturing process. Some are well within your control as a PCB designer to correct, and it will help you, in the end, to pay attention to them. Let’s take a look at some of the issues that could cause PCB manufacturing problems, and how you can best work with the engineering team of your contract manufacturer to avoid them.
Many PCB Manufacturing Problems Relate to Materials and Components
As a PCB designer, you know the product you are designing for, and you likely have a lot of experience creating and laying electronics out on a circuit board. Where a lot of PCB designers start having difficulties, however, is in setting up hardware designs for reliable and efficient circuit board manufacturing.
Most PCB designers don’t have as deep manufacturing expertise as they do design, often simply because they don’t have direct access to the intricacies of PCB production. As a result, they may miss design and component issues that will cause manufacturing problems. Quality CMs, on the other hand, have years and years of experience working on PCBs from a variety of industries and can partner with you to help mitigate these issues.
When it comes to PCB production, there are two key areas where manufacturing problems can arise:
- Materials: When it comes to the materials needed to fabricate a PCB, for instance, there are certain materials that are optimal for specific circuits. If different materials are specified in the board layer stackups instead, they ultimately won’t provide the best signal integrity performance. There are also cases in which the materials requested for the design aren’t suitable for the operating environments of the board or cost effective in its manufacturing.
- Components: Some components that designers choose for their designs may be standard components they’ve been using from their libraries for years, and they may not realize that the status on those components has changed over time. They may have long lead times, or they may simply be unavailable. The CM will be able to verify the status of the components in the design and make recommendations on their replacement if necessary.
In both of these areas, a CM should have the expertise to identify problems a designer may not even be aware of and mitigate them.
Specific Design Problems That Affect Manufacturing
Layer stackups and component issues are the big-ticket items, but there are a lot more potential manufacturing problems lurking deeper that the designer should be aware of as well. Here are a few of those for your consideration:
- Fiducials: These markers serve as targets to help align fine pitch parts, such as QFPs or BGAs. If your design doesn’t include them, it could cause problems for assembly.
- Proper clearance: For automated assembly and test equipment, you need to make sure that you’ve given your components enough clearance to mechanical objects, the edge of the board, and to each other.
- Component-to-component placement: As the circuit board is going through the wave solder, components that are too close to each other or rotated incorrectly can cause problems. For example, if taller components precede shorter components into the wave, it can result in a shadowing effect, which reduces the strength of their solder joints. Chip components rotated perpendicular to each other can result in the same issue.
- Tombstoning: This is an effect that can happen when unequal heating is applied to a chip component during solder reflow, causing it to stand up on one end instead of both ends soldering down as they should. The cause of the unequal heating can be either incorrect SMT land pattern sizes used for the part or different trace widths coming from the two pads of the part and the wider trace acting as a heat sink.
All of these issues can potentially cause problems for your PCB during its manufacturing. The key is to use good design for manufacturability (DFM) practices during the PCB layout to make sure that you avoid them. Here is where your CM can help you to understand the DFM practices that you need for your specific design.
Partner With your CM to Resolve PCB Manufacturing Problems
When you work with a quality CM, you’ll find that they are a great resource for DFM information and working with them to perfect your design is the best way to ensure error-free manufacturing.
To do this, your CM should have a team of engineers that can review your design for DFM issues and make recommendations to you for production enhancements. There should also be a team of component engineers that can review your parts to ensure you won’t be surprised by parts that aren’t available or not recommended for manufacturing.
Of course, there may be times when you have a board that you need to rush through manufacturing for a quick prototype, product demo, or proof of concept, and you don’t have the time to resolve all of the DFM issues. Fortunately, most CMs have the ability to work with what you have to help you through. In some cases, the CM can make quick changes. Other times, they will correct manufacturing problems on the fly during production. The real key is to work ahead of time with them and get as many DFM issues correct in the initial design as possible so there is less to clean up later.
Preventing common PCB manufacturing problems means working with a CM that’s highly skilled in meeting your needs. Choosing a partner with the right experience and expertise can ensure you get even the most difficult PCB designs built and completed to your satisfaction.
