7 Electronic Design Problems that Add Hidden Expense
When developing a product or electronic assembly significant efforts are placed on functionality and on reducing time to market. Often Design for Manufacturing (DFM) takes a back seat without realizing the long-term consequences. Even if the manufacturing cost of a product is within target the manufacturability should be considered and addressed. Products that are challenging to build will typically result in longer lead times, lower margins, and possibly lower quality in the long run, than products that are designed with manufacturing in mind. In our experience we have identified several common electronics design issues as described below.
1) Over tolerance / over dimensioning
Tight component tolerances may be necessary, but the cost to make the product is directly correlated. If your design margin can tolerate 5% or 10% resistors do not specify 1%. Similarly mechanical tolerances should be only as tight as needed to ensure functionality of the product. A Contract Manufacturer (CM) will build according to their customer’s requirements to meet the tolerances of their finished product. To help reduce cost and avoid additional delays make sure tighter requirements are necessary before adding them.
2) Mixed Technology
Mixing different technologies on a PCBA (e.g. SMT and thru-hole components) will likely increase cost and manufacturing time. Minimizing mixed technologies and designing for as much automated assembly and SMT placement as possible will reduce manufacturing complexity and cost, while improving quality. Always look to minimize hand component placement and other manual secondary operations.
3) Electrical Testing
All devices should be electrically tested at the location of build. Even basic testing is preferred to none. This step in manufacturing is vital to ensuring that only quality product ships and provides near real time feedback to the manufacturer on performance or quality issues. This will save time and cost in the long run by allowing correction or rework of failing product before shipping to the customer. Planning for functional testing at the manufacturing location is always preferred, and should be considered as early as possible in the design cycle.
4) Electronic Component Placement
Most automated equipment at a Contract Manufacturer relies on conveyors and fixtures to transport products through the process. Components placed close to the edge of the board (unless critical to design parameters), at odd angles, or not following good practices for design layout and spacing may require additional paneling/tooling to facilitate fixturing, and add manufacturing cost.
5) Component Sourcing
Many products require tight control over component sourcing approved vendors, or have only single sources available. However, wherever practical, components should be chosen with multiple alternatives available and included in the approved Bill of Material. This can save cost by allowing for competitive sourcing or elimination of minimum buy quantities. This can also dramatically improve lead times due to the increasing scarcity of components in the marketplace, allowing for substitution of available components without requiring significant additional testing or approvals.
6) Component Sensitivity
For many applications moisture and temperature sensitive components cannot be avoided. When designing electronics and selecting components, consider factors that will affect manufacturing process flow, such as components that cannot withstand SMT reflow profiles or can’t be exposed to a water wash process. These components will require hand placement which requires significantly more labor than an identical functional part that can tolerate these environments. This will lead to an increase in total assembly cost.
Some common examples include:
a) LEDs, switches, and connectors often can have a wide range of heat tolerance. When used on a RoHS PCBA ensure they are compatible with reflow temperatures for RoHs processes.
b) Variable resistors/capacitors/switches/connectors ‐ many of these cannot be washed and some cannot be conformal coated. If you intend on using water wash or flux make sure to specify components that are compatible with the process.
c) Conformal coating/RTV/underfill: For projects considering use of any of these processes in assembly, work with your Contract Manufacturer during the design phase to determine the optimal process and materials to select. Specifying a unique material or unconventional process will require additional development time and may increase product cost significantly.
7) PC Board Design
Similar to the component and process considerations above, a Design for Manufacturability review should be conducted on the PCB design before transferring to production. A number of factors including layer count, component density, panelization design, fiducial markers and required assembly tooling should be carefully reviewed and optimized prior to finalizing the PCB design. On many BOMs the most expensive and longest lead component will be your PCB, for this reason clear communication with your board house (or CM) whenever possible during design and prototyping will prove invaluable to achieving the highest quality and lowest cost PCB design.
Design for manufacturability and test should be considered as early in the development process as possible. This process helps reduce product cost, improve lead times and ensure highest product quality. Delaying these activities until after the design is completed can make it difficult or impossible to incorporate suggested changes. Valtronic has expertise in all areas of DFM and DFT and is here to help.