Design for manufacturing (DFM) has evolved over the years from being an approach for dealing with efficient use of wire, cables, and mechanical hardware, to one which can be applied in a broader manufacturing scope. Simplification and standardization of product design is the ultimate purpose of applying DFM principles in the manufacture and development of new products.

A typical manufacturing system (Figure 6-1) is comprised of many sub systems which allow a cost effective and modular approach in making the manufacturing process more efficient. Early participation by all the product segments, from design to quality, is essential to the principle of DFM. The majority of the resources for manufacturing have been expended by the time it leaves the design stage. DFM should start with the proper documentation and subsequent application of design rules for product manufacturing, including the selection of printed circuit board (PCB) materials, components, tests, qualification standards, and assembly process. It is also advisable that commercial off the shelf (COTS) parts should be utilized as part of the standardization process. This is not always possible, especially for high end military hardware requiring special environmental and qualification standards.

The EMPF is constantly faced with the challenge of converting new process technologies into manufacturing ready systems that can be used in a full scale production environment. We are often asked by our customers to review prototype, proof of concept designs, and to subsequently seek solutions that will reduce cost, maintain performance, and increase yields when scaled to manufacturing volumes. For high reliability applications, such as the ones for military avionics, the importance of proper DFM becomes more critical.

DFM for Product Design
Given that the acronym DFM does stand for design for manufacturing, it stands to reason that product design should be considered an important primary step, a
gatekeeper of sorts, for subsequent manufacturing operations. In the area of product design, some of the elements of DFM that should be incorporated are the following:

• Customer Requirements. Are the operational requirements for the design being met? Are there changes that must be made to the customer design, and is there a system in place for risk management?
  
  
• Material Sets. Are there special material considerations that would preclude restricted materials and present potential incompatibilities to specific material sets?
  
  
• Preferred Parts List. There should an updated bill of materials (BOM) with a preferred parts list, which includes contingencies in the event that the specific parts requested in the design could not be secured. Keep in mind that in many military applications, the time between design approval and manufacturing could be a matter of years. Parts may no longer be available and suitable replacements will have to be used.
  
  
• Safety Analysis. This is especially relevant for military equipment, where an analysis of the critical systems must be vetted thoroughly for reliability. This includes outlining the safety requirements, incorporating them as part of the design system, and assessment at the prototype stage. For military applications, MIL-STD-822 and MIL-STD-1629A provide the standards for safety qualification.
  
  
• Manufacturing Plan. The plan should include a Production Readiness and Manufacturing Technical Data Package that outlines the specific details of the manufacturing process that will be used to produce the particular assembly. It is critical that manufacturing personnel be involved in the process during the design review, to ensure that the manufacturing protocols called out for the design are within the capability of the equipment and manufacturing infrastructure to support it. For example, manufacturing processes for a Pb-free assembly require higher temperatures and substantial changes in equipment, processes, and training in the areas of solder reflow, including paste and wave solder, cleaning, testing, and inspection.
  
  
• Reliability Requirements. The lifetime requirements and environmental qualifications should be defined for the system, assembly, or sub assembly. This includes defining the environmental conditions in which the product will undergo in qualification testing.
  
  
• Sustainment Plan. The reduced availability and increased cost of many electronic devices and parts has made the task of sustainment more difficult, and has had a profound effect on all the elements of logistic management. Anything from configuration control, design traceability, part replacements, and material compositions can be affected, especially for military hardware where long lead times from design to manufacturing are common.

The EMPF has been proactively involved in training engineers on the principles of DFM. By customizing our courses to their specific needs, they are given the opportunity to maximize their skills and utilize the available resources at our facility in Philadelphia. For more information about DFM, please contact the EMPF registrar at 610.362.1295, via email at registrar@empf.org, or find course descriptions on the web at http://www.aciusa.org/courses.