Issue link: https://iconnect007.uberflip.com/i/1233021
28 DESIGN007 MAGAZINE I APRIL 2020 er volumes, and techniques to reduce the cost so that a profit would be realized by selling the product in volume. However, a spy satellite or a control mechanism in the cockpit of an air- plane will most certainly be more costly due to its limited volume of production and it's higher reliability requirements. The components and parts used in the product have to undergo rig- orous testing, which all add cost to the individ- ual components, and that will add cost to the overall product. Then, there are the specifica- tions and regulations that will add to the time- line and cost. Shaughnessy: Do you start looking at costs at the schematic stage? Dack: We can and should. A long time ago, when CAD databases began including attri- butes that could be populated within the sche- matic, somebody had the great idea to create an attribute for cost. In other words, a sche- matic symbol represented an off-the-shelf part. The part would correspond to a data sheet and a supplier, and the supplier's costs could be added as an attribute. However, all one needed to do was try to pur- chase those parts. You'd find out that depend- ing on the supplier, inventory, or lead times and production quantity, these parts often ei- ther were not available or the cost had changed significantly from the time of prototype. The parts would then have to be ruled out because they were perceived to be too costly. On the other hand, if the product were aimed toward volume production in the millions, the costs would go down and be more suitable. Now, we're seeing schematics being linked directly to online component sources—such as DigiKey, Mouser, and Arrow—who will give up-to-date data, cost, and availability for parts throughout the development cycle. This is a lot more dynamic, and I think it is the go-to meth- odology for engineers now. But my perception is that we start first and foremost with a BOM. Any EMS provider will require a BOM to initiate raw materials analy- sis. Time and process analysis will come af- ter the BOM is presented. A BOM will contain all the electronic parts, mechanical hardware, processes, process materials, and mechani- cal hardware. The BOM will most likely be re- viewed by a quoting team, which will break down all of the part classifications. And then there's a manufacturing engineer- ing group, which will analyze all of the parts, including the raw PCB to access all of the man- ufacturing processes that will be associated with the parts to calculate their manufactur- ing time, which is measured down to seconds per step. Any seconds they can shave off of the manufacturing process has the potential to result in huge cost savings in volume produc- tion. Shaughnessy: A few weeks ago, you mentioned that cost-aware design techniques are often just a matter of conflict management. You said it was tough to squeeze profit out of a design without messing with time to market, DFM, DFA, etc. Dack: It is conflict management or the con- vergence of all of these disciplines. Often, we are put in the position of robbing Peter to pay Paul, with Peter being the electronics engineer, and Paul being the manufacturing engineer. Here's an example that's so common it is al- most cliché. Many times, an EE will require that SMT decoupling or bypass capacitors be placed as close to a through-hole pin as possi- ble for reasons of performance. If the board de- sign is two-sided, the EE will want those chip caps on the opposite side of the part, snuggled right up on the pin. Here's the rub: Design for performance says that the capacitor must be placed as close to the pin as possible, but DFM says that that sur- face mount capacitor will interfere with the solderability of that pin if it's not placed a hun- dred thousandths away from the pin. The de- signer is put in the unique position of having to deal with those two opposing forces. It must be our specialty and expertise to present both viewpoints to the engineering stakeholders and bring them to a solution agreeable to each of them, respectively. A cost attribute must be placed upon each so that an agreeable cost can