Perhaps it’s happened to you. The circuit board your contract manufacturer just delivered back to you has an intermittent component failure. You’ve been waiting to get this hardware in your hands for testing and debugging, and now that it is here, it isn’t working at all as you had expected. The problem, of course, is that there is a PCB component failure, and now your job has become even more difficult. Before you can work on what you need to, you have to first find and then fix the failing component.
Managing components correctly to minimize or eliminate the possibility of component failure is a critical part of circuit board manufacturing for CMs. To ensure you don’t have to deal with component failure problems on your builds, you should know upfront what your CM does to control their part inventory.
A CM is dealing with thousands of components in their inventory. It might be months or years between builds using a certain part. To avoid component failures, your CM should have a strict policy in place for inspection and testing. Let’s take a look at some of the problems that can happen without an adequate inspection, and then some of the inspection techniques your CM should have in place to prevent these problems.
PCB Component Failures to Look Out For
The components used on your PCBA builds could have a number of problems. Some, in the case of mechanical or electrical failures, could result in intermittent or complete failure of the board to operate as it should. Others, such as if an incorrect component was used due to a mislabeled part number, could also cause intermittent or complete failures, but it could be difficult to find because the component itself is actually working correctly.
Here are some of the component problems that may be encountered:
- Cracked cases or other visible damage.
- Broken or bent leads.
- A wrong part number or manufacturer identification.
- Components that have been previously used but packaged as new.
- Counterfeit parts.
- Components that are older than their date codes.
- Missing supporting documentation.
These component issues can result in the following problems on your PCBA:
- Total failure of the part, leading to the total failure of the board.
- Intermittent failures on the board due to broken or bent leads.
- Incorrect parts used on the board due to mislabeled part numbers.
- Counterfeit or out-of-date components could invalidate board certifications and approval.
- Missing documentation could invalidate certification, especially in the medical industry.
All of these issues can spell out big problems for your circuit board. To ensure the quality of your PCBA, your CM should have well-documented component inspection processes in place.
Inspection Techniques Used by Quality CMs
A contract manufacturer will be dealing with parts that have either been ordered out of a catalog of parts, or a part that has been specifically built by a manufacturer for customers that request them. For any of these new parts, there should be a full, first-article inspection process in place that will do the following:
- Take sample measurements of the part.
- Have the part reviewed and approved by a quality engineer to match up with the posted specifications.
- Maintain a file for this and all other first-article parts for future reference.
- In some rare cases for specialty parts, conduct an electrical test of the part with the help of the CM’s test department for a test fixture and procedure.
The more unique the part is—and for those that are custom-ordered for a specific application—the more thorough the inspection process should be. The inspection results should also be fed back to the manufacturer for their records.
Once a relationship has been built with a supplier of standard components, the parts may no longer need to be subjected to the same level of inspection. This should follow a documented criteria for inspection that will specify what needs to happen before a component and its supplier becomes a trusted part and vendor.
For instance, if a standard catalog part is received five times from the same originator or supplier and there isn’t a rejection, the moisture barrier packaging may no longer need to be opened for incoming inspections. This trusted relationship is vital with incoming components so that the components can stay in their protected packaging until they are needed for a PCBA build.
Inspection of incoming parts should also be determined according to the risk level of the part being inspected. Although each and every part will have a documented inspection process, that process will vary according to the risk level of the part. From the highest level of risk that requires the most detailed inspection down to the lowest level of risk, the risk levels for parts are broken down as follows:
- Build-to-print (BTP): BTP parts are manufactured for the CM according to your specifications. Examples of these parts would include the raw fabricated PCBs, sheet metal, plastics, and cables.
- Original equipment manufacturer (OEM): OEM parts would include components such as plug-in daughter cards, power supplies, and panels. Anything that is designed and controlled by the manufacturer, not by the CM or you.
- Commercial off-the-shelf (COTS): These parts are cataloged electrical components that are obtained through a distributor.
- Hardware: These parts include screws, nuts, and bolts, as well as solder, wire, and adhesives.
There should also be a risk hierarchy for the suppliers according to type, ranked from the highest to the lowest:
- New supplier for the first few orders.
- Established suppliers on the first receipt of parts
- Established suppliers on multiple receipts of the same part number.
- Service provider for hardware.
Clearly, there is a lot that needs to be considered and looked at when inspecting components to prevent failures. However, not all CMs will put as much effort into this as they should. Some CMs will purchase parts frequently enough that they send them straight to stock without any level of checking. They don’t take the time to see if they’re the correct part, or even if they are packaged correctly. This is why it’s vital to work with a CM that has the processes in place to stay on top of component failure prevention.
Choose a CM That Prevents PCB Component Failure
To ensure your PCBA is guarded against component failure, your CM should have a documented system for checking incoming parts and a procedure to establish a risk analysis of component vendors. Your CM should also conduct some level of inspection of all parts that will be used on your board. Component failure prevention shouldn’t be an afterthought or just for show, it should be well integrated into the entire manufacturing process of your CM.
At VSE, every part that comes into our facility goes through inspection before use. Because we won’t allow your board builds to be at risk of faulty components, there are some fundamental things we always check on every incoming part. This is built into our overall process to ensure the success of your project.
