There is always a degree of churn across the CEM world, of customers trying to reduce manufacturing costs by moving products from one CEM to another and creating tight competition. This is quite understandable but sometimes by the manufacturing stage the tricks for saving money have already been missed and the CEM ends up having to charge for unnecessary work built into the product due to the lack of Design for Manufacture (DFM).
A common response to improvement suggestions is that the design team are working on the next product so the CEM has to just get on with it. Products need to be designed with cost of manufacture in mind but this is too often overlooked in the rush to get a product ‘out there’. There are a number of factors here, which should always be considered before release.
In some cases the BOM can be a ‘give away’ that a design has been raised with poor consideration to cost. A long list of different resistor and capacitor types and values in quantities of one or two per unit can often, with care, be rationalised into fewer types and values. This then means that less part types need to be quoted, ordered, stocked, loaded to machines, fitted, inspected etc. and this makes a product cheaper to produce. Some of the more successful companies with lean designs have limited inventories of approved components and values, but many others are unaware or are even complacent about their designs.
A myriad of other design factors come into play for the production process itself. For example, can all components be fitted to one side? Can automatic rather than manual processes be used to fit and solder components? Is sufficient spacing allowed in certain areas? Are there fiducial marks to aid accurate placement?
In general, the more stages of manufacture the more the cost will be, so if all conventional components can be fitted to one side they may all be wave solderable in one stage. If not, there may be additional hand fitting and hand soldering to follow.
It always pays to talk with your chosen CEM to obtain honest feedback as to how to minimise costs. Helping the manufacturer to minimise costs will increase the prospects for the design in the long run.
At present, there are other factors affecting cost and availability. Component allocations are making electronics manufacturing a difficult world as components are increasingly placed on 16+ week leadtimes. Again, there may be some influence to play at design stage. There are certain component manufacturers who are renowned for poor availability of their product and some readers will know exactly who these are from bitter experience. Unfortunately, some of them are innovative parts, which give an edge to the end product. However, if parts are not available in time to get the product to market then sales may be lost anyway, so designing in an alternative may prove more successful in the long run! Again, it can pay to speak to the CEM about potential availability issues before costly testing and approval of a design only to find that you are committed to specific parts and future problems.
In short, the better the design, the easier to buy and build, the higher the manufacturing yield and the lower the product cost will be. This is why CT Production believes in providing a DFM report with all prototypes, and working closely with customers to minimise costs, to help in making a product suitable for manufacture.
Alan Trevarton Managing Director
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