A Checklist For Improving Product Design

There is a saying that what costs $10 to fix in design, costs $100 in production and $1000 out in the field. Good designs are more cost efficient to produce, have less defects in manufacturing and are generally more reliable in the _FBP5218-2field. What common design mistakes should you avoid in your next product development effort? Here are eight issues we’ve seen:

Issue 1: Lack of Proper Protection on I/O (Inputs/Outputs).  Most devices need to take input signals and output a signal to other devices out in the field.  These are generally connected via hard wiring.  This hard wiring can be susceptible to external electrical noise or power surges due to other devices or lighting strikes and electrostatic discharge (ESD).  When this happens, it is very possible for this unwanted noise to be induced onto the wiring going back into your system.  Sometimes minor, but sometimes major damage can occur making the product malfunction.  To prevent this, it is vital to design protection circuits that shunt the unwanted energy to ground.

Issue 2: Lack of Proper Power Conditioning.  For any electrical product, it is important that the incoming power is conditioned to accommodate fluctuations in power, brown out conditions, missing AC cycle and power outages.  There are a number of ways to accomplish this.  Many active ICs have some power conditioning built in and some even have the ability to monitor the power.  Otherwise, utilizing simple resistors, capacitors and inductors in various topologies accomplishes sufficient power conditioning for most designs.

Issue 3: Design for Manufacturability (DFM) Guidelines Ignored. As I always say, you only design a product once, but you build it many, many times.  Following good guidelines not only controls cost, but also ensures good quality.  Follow proper spacing when routing traces, placing vias/pads, and placing components.   Maintaining minimum distances to stay within “standard” capabilities for both fabrication and assembly results in good quality at a lower cost.

Issue 4: Design for Test (DFT) Guidelines Ignored. Process control requires a mechanism to monitor the process.  Electrical test can serve as that mechanism.  Providing at least one testable-sized via for each net on your design is good practice.  Test fixturing has become more of a commodity these days so the cost of fixtures has dropped significantly.  Keep the test pad (which can be a via) at least 35 mils diameter size and minimum 75 mils diagonal spacing to adjacent test pads.  Keep test pads minimum 75 mils from body of component and 25 mils from a component lead.  Following these two design guidelines will allow for good test coverage utilizing a lesser cost fixture.

Issue 5: Insufficient Filtering of Integrated Circuits (ICs). Placing filter capacitors (aka bypass caps) onto each IC is required to provide enough localized potential energy to allow the IC to switch properly.  The other function they serve is to filter out AC (or DC ripple) voltage as not to interfere with the function of the part.  Not having bypass caps in place may cause the IC to switch states unintentionally.

Issue 6: Insufficient Bulk Capacitance. Bulk capacitance is required to maintain proper voltage levels throughout the entire board.  Depending on board size, there may be multiple sets of bulk capacitors used.  Because the power source or power supply may not be able to provide sufficient power to all parts of the board, the bulk capacitors help provide the additional energy as needed. In other words, they help load level the supply(s).

Issue 7: Insufficient Protection for Uncontrolled Incoming Power Loss. Linear regulator protection is required to account for uncontrolled incoming power loss.  When this occurs with insufficient protection, the current will want to go through the regulator in the wrong direction, possibly damaging the component.  Ideally, a diode should be provided to shunt the current around the regulator instead of through it.

Issue 8: Failure to Utilize PCB Design Good Practices. Most products sold into market need to comply with certain agency standards, i.e. U.L., FCC, CSA, CE, etc.  In order to pass many of these standards, employing sound EMC (electromagnetic compatibility) practices is key.  The compatibility part of EMC means that a design cannot emit any electromagnetic interference nor be effected from induced electromagnetic interference.  Following the practices mentioned previously will all help with ensuring the product complies with EMC requirements.  Additionally, if you remember what was taught in basic circuits class, current (I) flowing through a wire will create an electric field.  As a result the more wires carrying current, the more fields are produced.  And a trace on a board is really nothing more than a wire.  So keeping all wires a short as possible with the least amount of resistance reduces the magnitude of the electric field(s).  These can be mitigated by providing sufficient power and ground planes which ultimately reduces ground loops.  And one more thing to remember, a loop of wire with current traveling through it is really an antenna!  This is not good for passing EMC testing.

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Can Your Contractor Really Help Your Team Build Better Product?

Many companies assume that regional electronics manufacturing services (EMS) providers are more focused on building product, than helping customers build it better. That couldn’t be farther from the truth at Burton Industries. Engineering strength is one of one of our key advantages. For over 35 years, our team has been telling customers to ‘bring it on.’ Here are few examples of the problems we’ve solved:

Cost Reduction teamcrop

Many of our customers face competitive cost pressure but have limited redesign options. Our team can help. For example, in one measurement device product line we were able to apply our value engineering skills and reduce the cost of three assemblies by 12, 14 and 16 percent, respectively. The cost savings was achieved through a combination of identifying drop-in replacements for several components and eliminating some manufacturing processes.

Failure Analysis

In another case, we helped a customer address a field return issue on a system controller. Our engineering team performed failure analysis on the field returns using an outside laboratory and found no issues with the components. Further analysis showed that the problem was in the customer’s documentation. On the same assembly, a customer-initiated ECO had changed a component in error and created performance issues in the assembly. Our team worked with the customer’s team to evaluate and re-layout the board. The re-layout of the board corrected the design issues and reduced unit cost by $7.87.

Manufacturability

When a customer transferred an industrial product subassembly from another contract manufacturer, we found that design for manufacturability (DFM) analysis had never been performed. Not surprisingly, the product had a history of quality issues. Our analysis found incorrect land patterns and spacing, incorrect hole sizes, slot dimensions and locations that were missing. Components were also placed too close to the PCB edge.  We were able to re-layout the printed circuit board assemblies (PCBAs) to correct these issues.

Legacy Product

In yet another case, a medical OEM had a legacy product that needed redesign support. Our engineering team worked with customer’s engineering team to gradually convert the older PTH product to SMT, and provide DFM/DFT recommendations. The end result was more manufacturable product and improved component availability.

These are just a few of the many challenges our team solves on a day-to-day basis. We stand ready to provide a wide range of engineering support, including: design for manufacturability and test recommendations, smooth new product introductions, product lifecycle management recommendations, cost reduction suggestions and test strategy optimization.