Today’s electronics products often need to push the bounds of technology and of beauty. They also have to do that within increasingly tight timescales. Products need to hit launch dates for reasons including exhibitions, key meetings, contract renewals or to get ahead of competition. Increasingly this means that product development must be an extremely concurrent set of activities. There simply isn’t time to complete key project aspects consecutively.
Is your product development AGILE?
Where project deliverables can be changed and tweaked with low impact on the project schedule and budget, then dynamic changes with concurrent development can work very well. In part this is helped and driven by the Agile software development movement. Agile has increasingly gained acceptance over the last 5-10 years. It is an approach that embraces change and doesn’t look too far ahead. Agile allows for, and expects, the requirements to change and morph. It puts little effort into planning features which may well disappear.
This approach becomes much more challenging, risky and potentially costly when dealing with elements of the product which need to be physically manufactured. These project products have a lead time and cost associated with them. Changes can easily push a project off schedule and off budget. Unfortunately, the two most significant project elements, with long lead times and potentially high costs for change, are the enclosure plastics and the electronics printed circuit boards.
The Impact, and Cost, of Changing Designs
There’s pressure on product designers to commit to a design as early as possible in the project. Tooling is often on the critical path of the project and can have a typically eight to fourteen-week lead time. Tooling costs can be reduced by going overseas but this can add to the risk and timescale pressure as late adjustments to the design more difficult.
Changing plastic enclosure design after the injection mould tooling is in place means the tool is taken out of service. This is a risk to the product launch schedule as finalised enclosure plastics and sign off for the product assembly and test processes may be held up.
Tool modifications frequently involve modifying both halves of the injection mould tool. These modifications can involve welding, machining, polishing and re-running prototype runs. Modifications can take some weeks to complete. Occasionally, if the modification is complex or affects a larger area of the tool, it may be necessary to write off the old tooling as the modification may affect the tools mechanical operation, plastic injection point, gates or the cooling waterways.
Printed circuit board changes, to modify their form factor to accommodate an enclosure change, can cause much of the circuit board to ripped up and started again. On tightly packed printed circuit boards the movement of, for example, a connector can then have knock on effects. The need to move the processor, memory, power supplies (and more) adds time and cost. It may be that the change can be readily accommodated, but this is relying on luck which inevitably runs out at some point.
Which comes first – the plastics or the pcb?
Once the product has been assembled the enclosure is the main element that the customer will see. This is largely responsible for the product first impressions, will be featured in product marketing and must be well thought out and beautifully designed. A good enclosure therefore boosts desire for the product which translates into increased sales.
The internal electronics will also contribute to the marketing, often through the comparisons of key technical specifications. Using the example of a mobile phone this could be:
- processor speed
- memory size
- battery life, and
- camera specification.
These are just headlines and are often only experienced once the product is being used. This is when the quality of the internal electronics becomes important, either further delighting the customer or causing disappointment.
The electronics, together with firmware and software, are responsible for the products battery life. Whether it gets hot, whether the product often and needs to be restarted and other important aspects.
It is clear therefore that both project elements are equally important, but for very different reasons. External factors will influence the project approach. Factors such as whether the design is completely new, a refresh of plastics, an upgrade of electronics within a pre-designed case or the use of an off the shelf box drive the decision here.
Does this change for Product Enhancements?
Where the plastics are already fixed, perhaps having been completed earlier or being reused from a prior product, the electronics must make the best of the available space. In this situation the mechanical model of the enclosure is the baseline to work from. This model should have fixed positions for large electronic components: connectors, screen, speaker, buttons, and lights. Here, the electronics designers import the mechanical model and then work around the constraints provided. There is a risk that the electronics may not fit within the enclosure. It is likely there will be some design compromises which may reduce the performance of the product. This has to be taken on a case by case basis.
Some of the compromises impact on the manufactured cost of the product. It may be necessary to add mezzanine printed circuit boards and/or to populate components on both sides of the pcb. This adds cost due to increased production processing time, additional connectors and more complex assembly.
A similar approach applies when using an off the shelf box. There may be a little more freedom with the location of large mechanical items and user interfaces, as the enclosures can be milled and modified to suit. Where the electronics are too large there are often a range of off the shelf boxes in a variety of sizes.
Where the electronics are not being changed but the enclosure is being refreshed then this situation is exactly reversed. The printed circuit board with its mechanical skyline is the fixed datum for the enclosure to work around.
New product design approach
For new products the process becomes more fluid. The aim here is to ensure that the enclosure and electronics are optimised for aesthetics, ergonomics, functionality, performance, process costs and assembly. Product designers and electronics engineers have to work closely together, exploring the possibilities and agreeing on the size, shape, keep out areas, height restrictions and major component positioning.
The electronics designers can help here by identifying the major functional elements of the design which would have a mechanical impact. These components can be added to on an outline schematic, together with pcb footprint and the mechanical component models. Critical connections such as those to radio antennas, high speed digital nets, differential pairs, impedance controlled traces and the like should also be connected up. The printed circuit board elements can then be iteratively placed and routed to ensure that the mechanical and electronic design come together. By only routing critical nets the time for this is reduced compared to that of the full printed circuit board.
This minimally routed printed circuit board can then be imported into the mechanical model. Various “what-if” exercises can be tested, including:
- Can we move the left edge in 5mm?
- Can the design be split into two boards to reduce the product length?
- How much separation is needed between the two boards?
Each scenario can be tested without having to re-engineer the whole board. Of course, the designer must keep in mind that they are dealing with a partial design. There will be numerous small resistors and capacitors to add afterwards. Fortunately these are getting smaller so shouldn’t cause too many issues for experienced engineers.
After a few iterations the available size, shape and headroom for the electronics can be determined and fixed and the two teams can then continue their development in parallel with the occasional check on any items that then need discussion.
The project manager then has more confidence and less risk from the concurrent development which helps them deliver the project on time, on budget and to the delight of the end customers.