Nothing is 100% perfect 100% of the time.  Because of this the best systems are designed to thoroughly examine the failure modes when they happen, trace them back to a root cause and then eliminate those failures.  This is the ideal situation and when we talk about PCB failures it is important to differentiate from failures during the design-build-test cycle and failures during service.  Of course the customer is only concerned about failures in service, but to minimize the failures in service, we often need to create failures during the design-build-test cycle to identify the weaknesses and shore them up before the product design is ready for production. RiverSide Integrated Solutions (RIS) provides full circuit board and electromechanical assembly and testing capabilities.  Essentially this means we can develop and test circuit board inspection and testing schemes to make sure that the product performs well within its intended service. We can perform circuit board assembly testing, system-level integration testing, and thermal/mechanical stress testing depending on the product requirements. All of this adds up to a robust manufacturing process and high reliability in service.

ELECTRICAL ISSUES

If we just look at the manufacturing process first, there are a couple of things which can show up.  If your application requires a multi-layer board, then the alignment from layer to layer is critical.  Often there are vias  (small conductive channels which act as conductors to carry a signal from one layer to the next).  Its easy to imagine how a misalignment between layers can lead to a short circuit or an open circuit.

When it comes to placement of components, which can be a fraction of a millimeter in size, misalignment is also a very critical process.  If you add in the small area available for solder placement, then solder bridges (shorts) or open circuit conditions can occur.

Fortunately RIS uses an automated handling system for PCBAs that have a fully Automated Optical Inspection (AOI) system.  This system rapidly takes snapshots at various stages of PC board assembly and compares critical parameters such as solder coverage and component placement in real time before moving the board to the next level of assembly.  The result is that these types of manufacturing errors can be eliminated before the board goes to the next step and almost never show up in the finished board assembly.

In certain instances, we can offer a functional, custom, end-of-line (EOL) tester.  This would be used to power up the board, inject appropriate signals of the right magnitude into the circuitry and measure the response.  This would constitute a final, or acceptance test before packaging and shipping.

MECHANICAL ISSUES

Although PCBAs are thought of as having strictly an electrical function, they must handle some surprisingly tough mechanical issues as well.  Probably one of the simplest to understand is that fact that they are made of a variety of materials: copper, epoxy, solder, ceramics, and plated metals.  Each

component expands a little bit when heated and shrinks as it cools, and all of the solder joints, attachment points, the laminations of the board and connectors undergo tens of thousands of cold-hot cycles during their lifetime.  If the board is intended for outdoors use these temperature swings could easily be 100 ˚C for several days in a row.  Over time, these temperature-related stresses can lead to cracking and loss of proper electrical function.

It is very common to guard against this failure mechanism by subjecting the PCBA to a temperature regime that allows all of the components to “adjust” to temperature-related stresses.  There are a couple of ways to do this depending on the experience of the board designer.  A high temperate soak, often for 24 hours, performs a sort of annealing process, making the PCBA much more immune to cracking later on.  A more severe, but similar process is to have the boards cycle through temperatures from the lowest to the highest expected operating temperatures, taking some time to soak at both the hot end and the cold end of the cycle.  This is a more stressful thermal test and can sometimes act as a screen to weed out product that might be at the very tail end of the bell curve. RIS can accommodate either type of thermal conditioning depending on your needs.

Of course, the other mechanical issue that a PCBA may have to endure is a high shock and vibration regime.  This usually requires stiffening up the board through mechanical supports. Alternatively the board can be mounted on shock absorbers to effectively isolate it from the outside forces.  Usually either of these approaches is used in conjunction with added epoxy around the heavier components on the board too prevent them from shaking loose.  Validating the design against this sort of vibration environment can be done using standard “shock and vibe” test equipment and fixtures.

FIELD FAILURES

As you can well imagine after a thorough design cycle, automated assembly, testing and thermal conditioning most PCBAs are ready for a long service life. And you would be right – electrical assemblies are considered to be a highly reliable part of any system. At the same time some products do fail in service and most of the time it is within the first few weeks, especially if the part is a replacement part.  There are more reasons for this than you have fingers and toes, but we can illustrate with a simple example.

For a correct replacement procedure, all of the mechanical and electrical connections on the “old” part need to be disconnected, cleaned, inspected for cracking or wear-and-tear and the electrical connections should be checked for continuity.  All of these steps are not usually followed and a service call will often turn up some intermittent electrical connection, or perhaps even a voltage drop on the power supply due to poor contact. In retrofit situations, sometimes the power connector has been replaced, so it becomes necessary to modify the replacement part to match the existing installation in order to keep the system running.  Unfortunately the power line often gets miswired and the unit dies in a puff of smoke.  These types of field failures are created by well-meaning people trying to solve a problem quickly. Usually a phone call to the technical support line before doing the replacement will weed these out and save everybody a lot of time in the long run.

There are, of course, legitimate premature field failures and they need to be treated seriously. Where RIS has the service contract, give us a call, we’ll get you set with a return authorization (RA) number and keep you filled in as to what we found out and how the repair or replacement is progressing.

RIS is an advanced contract manufacturer providing robust solutions in circuit board assembly, product assembly, kitting, supply chain management, fulfillment, distribution, and reverse logistics. We employ more than 300 people and provide services to OEM’s across the world. We operate 3 state-of-the-art manufacturing facilities within the U.S, and as your one-stop-shop we have the capabilities, capacity, quality assurance standards, and resources to provide you with support for all of your manufacturing needs.

With all of the choices in contract manufacturers out there, we know it can be difficult to find someone that not only understands your business model but also has your best intentions in mind. RIS has proven to always be a win-win focused relationship. As your one-stop-shop, we have the capabilities, capacity, quality assurance standards, and resources to provide you with support for all of your manufacturing needs. We understand that supply chain management is difficult and very time consuming, so we urge our customers to utilize us in the fullest capacity. Our total-package solutions include:

· Extensive supply-chain network

· Purchasing and inventory management

· Dedicated Program Manager

· Warehousing and drop-shipping capabilities

· Flexible order fulfillment

· Product assembly: sub-assembly and full product

· Scalability to meet your needs

Contact us today at (507) 523-3220 to see how we can help with your manufacturing project, or click here for a quote.