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Why DFM can increase your revenue in Electronics

DFM is an acronym that stands for Design For Manufacturing. It is an increasingly important discipline in the Electronic Industry, because it plays a crucial role in New Product Introduction, by reducing costs, increasing quality and avoiding surprises during actual production. In this article we will see what exactly DFM is and how a tool like Valor NPI can help both designers and manufacturers in a truly DFM-based New Product Introduction process.

What is DFM, exactly?

In a general sense, DFM can be defined as the practice of designing products in such a way that they are easy and cost-effective to manufacture. Why is this so important? The importance of designing for manufacturing is underlined by the fact that:

  • about 70% of manufacturing costs of a product (cost of materials, processing, and assembly) are determined by design decisions;
  • only 20% of those costs can be attributed to production decisions (such as process planning or machine tool selection).

So if you want to keep under control time-to-market, production cost, and the quality of your product, decisions taken during the design stage are the most important. That is the field of application of DFM.

In the electronics market, Design for Manufacturing is applied to the Printed Circuit Board. Its production is composed of two different stages:

  • Fabrication, which consists in the realization of the "bare" board where components are placed;
  • Assembly, which consists in the placement of all components on the board.

Technically speaking, a distinction is made between Design for Fabrication (DFF) and Design for Assembly (DFA), because the problems that you can meet (and prevent) are different in the two cases.

DFM and the NPI business process
DFM and the NPI business process

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This paper discusses the eight steps that you need to take to ensure PCB assembly success and the success of the business, as well as how Siemens Valor NPI tools can help you achieve that success.

DFM and NPI

Both DFT and DFF are aimed at a successful New Product Introduction (NPI), the process of introducing a new product into the manufacturing process and eventually into the marketplace. In the ideal NPI you don't have any re-spin of the design with corrections, or implementation of countermeasures for issues in production.

Decisions made during PCB layout directly affect the success of the NPI process. Any manufacturability problem found in a design will cause a delay at minimum, or even the need of a re-spin.

The word "re-spin" is typical of this process. It is useful to underline its meaning. Re-spin is part of the slang of the industry. It essentially means to re-do, retry, make another revision, "back to the drawing board", to use an expression popular among designers. If you have to go back to earlier stages of the design process, then you need to go through all the steps again, including tests and verification. Every additional re-spin means higher costs and longer times.

The evolution of DFM

Some kind of DFM has always been adopted since the beginning of the Printed circuit boards manufacturing in the 1950s. In these decades, DFM has evolved dramatically, to the point of becoming an integral part of new product introductions (NPI). Today, NPI software spans design and manufacturing to optimize a PCB for manufacturability. It takes data and knowledge directly from manufacturing that can be used throughout design, fabrication, assembly and test.

Best designers find that NPI software lets them identify multiple ways to optimize their products during the initial release process, with embedded knowledge of the fabricators’ and assembly suppliers’ capabilities.

This approach of considering the needs of everyone involved in the whole process is called "intelligent DFM". It is intelligent because anyone can benefit from it: PCB designers, manufacturing engineers and electronics manufacturing service (EMS) companies or contract manufacturers.

Intelligent DFM

The "intelligent" approach includes also the use of expert system logic to automate DFM analysis. It is what Valor NPI software from Siemens does. High-quality automated DFM analysis is based on a combination of PCB technologies and manufacturing constraints. PCB technology can be automatically determined with intelligent design data. For example, the copper weight of each layer is critical in the fabrication DFM analysis. This is because of the etch compensation applied and, thus, resultant etch-back are going to vary based on the copper weight used.

Copper weight will vary between inner and outer layers. A 3-mil spacing on an inner layer made of 0.5 oz. copper could be acceptable. But more spacing is required on the outer layers - as much as 4-mil spacing based with the use of 1 oz. copper. In addition, sequentially laminated stacked vias require a different set of DFM rules than a conventional, single-lamination PCB.

Letting the DFM software act on each of these constraints automatically saves engineering effort and delivers the desired results consistently for every user, regardless of their manufacturing expertise. In addition, Valor NPI can perform a complete solder analysis, as shown in the picture below, to locate potential solderability issues.

DFM checking
Valor NPI can run solder validation analyses as part of the DFM checking.

Panel optimization

As DFM evolves continuously, now Valor NPI software is also used to design and optimize PCB panels. Many companies are inefficient in their panel-design process, even for assembly panels or arrays. Typically, designers will use a 2D mechanical CAD tool to create a drawing of what the assembly panels should look like when received from the bare-board fabricator. Several hours are required to create the drawing and add notes and dimensions, then they send it to their fabricator as a dumb drawing file. “Dumb” means the drawing file contains no intelligence that the fabricator can key off of in the tooling process. Instead, the fabricator must recreate the panel with their CAM software and send a proof image back to the designer for approval. With the technology available today, this level of redundant manual processes is unnecessary.

Instead, the design team can easily create assembly panels using the Valor NPI software and include all the elements needed: rails, tooling holes, fiducials and rout or v-score features. Valor NPI can automatically optimize the boards within the assembly panel to minimize the fabrication material costs.

panel optimization n DFM
Valor NPI can optimize both fabrication and assembly panels. Here, fitting the PCBs together in a more efficient pattern of assembly panels produces 20 assembly panels instead of the original design’s 12 panels.

Data digitization

Finally, new product introduction involves creation, validation and delivery of the design data package to the fabrication and assembly houses. Historically, it is delivered as a package comprised of some combination of the following:

  • Gerber files
  • Drill files
  • Netlist files
  • Test files
  • Manufacturing BOM
  • Drill drawings
  • Assembly panel drawings
  • Route drawings
  • Stackup drawing
  • Drawing notes.

For an industry that drives the digitalization of the planet, PCB production is heavily dependent on manual processes with instructions communicated through 2D, non-relational drawings and documents. Is there anything in documentation that cannot be represented as a data field? Nets that are intentionally shorted? A data field can be tagged to the appropriate nets. Top-side soldermask color?

With Valor NPI, data can be transferred from the design to manufacturers completely digitized. This is the essential premise for Digital Transformation of the Electronic Industry and for implementation of Smart Manufacturing.

The Valor NPI added value

The examples above made it clear what an intelligent DFM is and what is its role in the NPI process. But in the case of Valor NPI, the tool itself is able to give you an added value for at least three additional reasons:

  • it is really easy to use, with a quick learning curve and tangible results at the first uses;
  • it comes with the IPC rule set embedded inside the software;
  • the DFA solder joint check is included out of the box.

The Valor NPI Business Process

In conclusion, we can say that DFM is the true element of continuity between Design and Manufacturing. It belongs to the field of activity of Design, but it has the biggest impact on Manufacturing. As we can see in the chart below, in a lean NPI process - represented by the green line - fewer re-spins and better quality means the ramp to volume is steeper. As a consequence, the revenue is higher. That's the point.

Valor NPI Business Process in DFM
The Valor NPI Business Process

White Paper

This paper discusses the eight steps that you need to take to ensure PCB assembly success and the success of the business, as well as how Siemens Valor NPI tools can help you achieve that success.

Ivano Tognetti

Ivano
Tognetti

Product Manager

Ivano, at the forefront of electronics since
the 1980s, is Product Manager for the
EDA (Electronic Design Automation)
area. The management of projects in
various European countries gives him a
very wide vision of the market and its
problems.




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