The Art of Design for Manufacture

Vertica Asthana is a technical journalist at EFY

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Have you ever met with designers who were in stress when their prototypes failed? Or have you seen the production team’s anxiety when they were facing manufacturing challenges at production line? Or have you met designers who have had to face wrath of the buyers when their product failed and were questioned for the material used and the product’s quality?

In most such cases, it is found that a reliable design for manufacturing (DFM) was not used, by using which problems could have been avoided at the design stage itself. DFM makes a product reliable, sustainable and feasible after production.

Vikas Saxena, general manager – quality at MYBOX Technologies, cites an incident in 2005, when his company almost lost a deal with Ford Motors. During the time, he worked for an electronics manufacturing services (EMS) house in Milwaukee, USA. They were executing an order of Ford’s engine control unit boards, which started failing soon after production. They had joint meetings with Ford executives to find out the problem. They realised that since DFM was not used during the design stage, there was a fault in the circuit board where the layers had interchanged, causing a shorting in the boards. The EMS house had to abort the product’s development, losing tons of money.

When should you start the design for manufacturing process (Image courtesy: http://svv.io)
When should you start the design for manufacturing process (Image courtesy: http://svv.io)

Most electronics giants and auto firms use DFM while their product is in design stage. And DFM is usually done by using certain tools. The companies have their tools defined as per their own rulebooks. For example, IT giants Cisco and Jabil use Valor, which is an expensive tool but very important for them.

According to experts, DFM should be carried out where the production is to be done, as surface mount technology (SMT) machines differ from company to company. Saxena recalls an instance when a through-hole capacitor started coming out from its pad area during wave soldering, and hence the production had to be stopped immediately. It was found that, since the production centre was in Penang (Malaysia), there was a difference in the SMT machine used and its working, and hence the disaster.

Multinational companies (MNCs) like Jabil, Nokia, Cisco, Apple and GE follow DFM religiously. Jabil uses automatic machines, even for rework, for a perfect result.

Valor: For error-free design

Valor, the most popular DFM tool used by MNCs, provides a PCB manufacturing solution. PCB is the heart of electronics hardware and embedded systems. Valor is a seamless end-to-end ‘all-in-one’ tool. It helps minimise errors, so that in the long run the designing and manufacturing teams do not have to waste time, labour and cost in fault detection and rectification.

The design, after completion, is checked using Valor or a similar tool. Companies like Cisco have made the use of this DFM tool mandatory as it manufactures up to 24-layer complex printed circuit boards.

Valor has a long checklist that includes boards getting checked on printed circuit boards assembly, layer by layer, including signal check and pattern check on-component basis, count of components, Gerber files, impedance on the PCB, copper layers, copper pads, drill check and through-hole pads. Other than these, quality check of PCBs is done as per application, and thickness, routing, punching, stencil check and stencil paste are also taken into consideration. After the test, Valor differentiates between the hot points and the cold points. The hot points are rectified first, followed by the cold points.

Valor does calculations, too. DEK, a manufacturer of screen printing machines for SMT PCBs, needs to know precisely how much solder paste should be applied on the stencils; the transmission rate should be 70 per cent or more. Valor takes 24 to 48 hours to calculate, depending on the size of the project. Similarly, there are calculations required for some other processes, too.

Valor always has scripts running, and if a user wishes to add any process to it, a programmer will be required to modify the script. As per Saxena, Valor for electronics is a set of sophisticated DFM tools, but it does not have revised versions yet. However, if on-the-air changes are made in the software, it gets updated elsewhere simultaneously.

Valor users need to convert the SAP or ERP, CAD, PCAD files, or other PCB design and simulation files, into ODB++ format, which is a readable format for Valor.

Some other DFM tools

A tool called Apriori provides a distinctive platform for manufacturers to manage their product’s cost at all stages of its development and manufacture. This starts right from design stage to manufacturing stage. Apriori focuses on how the project cost can be made feasible and enables quick iterations as per changing market, material cost and availability.

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