How DFM and Advanced NPI Engineering Support Eliminate Hidden Costs in Electronics Manufacturing
In short: the unit price in an EMS quotation is only part of what an electronic product really costs. The rest is paid later: in PCB re-spins, rework, low yield, line stoppages, expensive testing and a delayed market launch. Most of these costs are built into the design long before the first production run. In this article we show where those costs hide, how design for manufacturing (DFM), together with DFA and DFT reviews and a structured NPI process, eliminates them, and how we run this work at Assel.
Where the cost of an electronic product is decided
Product development literature keeps repeating one observation: 60 to 80% of a product’s cost is committed by design decisions, even though the design phase itself usually consumes only a small share of the programme budget. Later manufacturing decisions have far less room to manoeuvre.
The second principle is the so-called rule of ten: the cost of fixing an error grows by roughly an order of magnitude with every stage it survives. A wrong footprint corrected in the CAD library takes a few minutes. The same error found in the first production run means a new board revision, a new stencil, new samples and weeks of delay. Found in the field, it means complaints, repairs and lost trust.
Siemens research from 2020 and 2022 indicates that almost one in three PCB projects misses its release date because manufacturability issues force additional re-spins. Earlier industry data put the average at 2.7 re-spins per new product introduction. Each of them is a cost you will not see in the unit price.
Seven hidden costs in electronics manufacturing
1. Board re-spins. New PCBs, new solder paste stencils, new prototype assembly, revalidation. In regulated industries, the technical documentation has to be updated as well.
2. Low first pass yield. Solder bridges, tombstoning, voids under thermal pads, insufficient fill on through-hole joints. Every defect means rework, and every rework adds thermal stress to the board and risk to reliability. For products with elevated reliability requirements, for example IPC Class 3 PCB assembly, the number and type of permitted reworks are often restricted by customer requirements.
3. Manual operations that could be automated. Components placed so that they require hand assembly, through-hole parts that cannot be selectively soldered because clearances are too tight, no room for grippers in electro-mechanical assembly.
4. Test cost and test limitations. Missing test points make in-circuit testing (ICT) impossible or force an expensive fixture redesign. Low test coverage lets defects slip through and surface at functional test or at the customer.
5. Panelisation and material utilisation. A poorly designed panel means more laminate waste, slower assembly, separation problems and mechanical stress during depanelling.
6. Material risk built into the BOM. Single-source components, NRND status, extremely long lead times or unusual packages. This cost appears months later as a shortage or a forced change.
7. Delayed time to market. The hardest to calculate, but often the largest. Every month of delay means lost sales and ground given to competitors.
DFM vs DFA vs DFT: what is the difference?
The acronyms are often used interchangeably, but they answer different questions:
| Acronym | Full name | Key question |
|---|---|---|
| DFM | Design for Manufacturing | Can the chosen process actually produce this board (tracks, clearances, holes, stack-up)? |
| DFA | Design for Assembly | Can the components be placed and soldered correctly and repeatably? |
| DFT | Design for Test | Can defects be detected and functions verified at a reasonable test cost? |
| DFR | Design for Reliability | Will the product survive its operating conditions (temperature, vibration, humidity) for the intended lifetime? |
| DFX | Design for Excellence | A holistic approach combining all of the above, plus cost, serviceability and component availability |
In EMS practice these reviews overlap. Footprint, solder mask and stencil apertures form one assembly decision, not three separate issues. DFT, in turn, starts with the question of what the test needs to detect, and only then selects access and method. That is why many teams talk about a combined DFM/DFA review.
What a good PCB DFM analysis checks
A thorough PCB DFM analysis on the EMS side, together with DFA and DFT, usually covers the following areas:
Board and stack-up
- whether track widths, clearances, holes and annular rings match the PCB fabricator’s capabilities and the required IPC class (reference standards include IPC-2221 and IPC-6012),
- stack-up symmetry and the risk of board warpage during reflow,
- via-in-pad and via filling.
Footprints and soldering
- whether land patterns match the component documentation and IPC-7351 recommendations,
- thermal relief on pads connected to large copper planes,
- stencil aperture ratios and the risk of insufficient paste release,
- thermal pads under QFNs and the risk of voiding; for fine-pitch parts, the requirements described in our article on assembly of HDI and ultra-fine pitch components.
Placement and assembly
- spacing between components for automated placement, AOI inspection and rework access,
- keep-out zones near board edges and around selectively soldered parts,
- orientation of polarised components, fiducials,
- heavy and tall components and shadowing during soldering.
Test
- presence and placement of test points for ICT or flying probe testing,
- access to programming and debug interfaces,
- whether testing can be split into stages, and the expected defect coverage.
BOM (often a separate review)
- lifecycle status, number of sources, lead times,
- whether packages match what is declared in the BOM,
- opportunities to standardise passive components.
At many EMS providers, the BOM review for availability and lifecycle is run by purchasing, while DFM is done by a process engineer. These are two different analyses: the first answers whether the components can be bought, the second how the product can be assembled most easily and reliably.
Panel and process
- panel design, separation method, tooling strips,
- sequence of operations: SMT, THT, selective soldering, cleaning, selective conformal coating.
The outcome should not be a checklist of “errors” to tick off, but a report that rates the severity of each issue and proposes a solution the designer can accept, reject or modify. Tools such as Valor NPI contain more than a thousand automated rules, and software vendor data suggests that concurrent DFM analysis reduces the number of re-spins by 57% on average. But tools alone cannot replace the experience of a process engineer who knows how a given design will behave on a specific line.
The NPI process as a system, not a one-off event
New product introduction (NPI) is a structured process designed to prove that a design can be manufactured repeatably, at the expected yield and cost, before a series production order is placed. Typical phases are:
- Feasibility and quotation – documentation review, initial BOM and risk analysis.
- DFM/DFA/DFT review – report and agreement on changes with the customer.
- Process preparation – machine programs, stencils, soldering profiles, assembly and test fixtures, work instructions.
- Prototypes and pilot run – first production with full inspection, first article inspection (FAI), defect data collection.
- Results analysis and corrective actions – process improvements and, where needed, design change recommendations.
- Release to series production – frozen documentation, validated process, final test strategy.
The key point is that DFM is not a one-time event. The first review catches design errors, but the pilot run reveals what files cannot show: how a specific laminate batch behaves, the real thermal profile of a large board, access issues during electro-mechanical assembly. A good NPI process closes this feedback loop.
In high-mix low-volume electronics manufacturing, NPI is especially important because new products and revisions arrive often and batches are short. There is no time to “work up to yield” during series production. We cover this in more detail in Why is the NPI process fundamental for high-mix low-volume PCB assembly?
How Assel runs DFM reviews and NPI
Assel specialises in high-mix, high-complexity projects, and our engineering team has thousands of new product introductions behind it. Every customer is assigned dedicated engineering support for the entire product lifecycle: from DFM analysis and industrialisation (NPI), through engineering change management, to the analysis of components being discontinued.
DFM analysis in Siemens Valor. We analyse customer designs in Siemens Valor, and the results are assessed by an engineer who knows our lines and processes. The issues we find most often are:
- footprints that do not match the PCB pads,
- problems with component placement relative to solder mask openings: risk of shorts, solder escape and paste printing issues,
- components placed too close to the board edge,
- PCBA cleaning constraints, i.e. whether the board can be safely washed in a cleaning machine (the cleaning compatibility of individual components is verified by the designer),
- test points with the wrong size, position or distribution between top and bottom sides,
- silkscreen that interferes with paste printing or hinders inspection, e.g. missing or unclear polarity markings,
- open vias in sensitive areas, especially in thermal pads.
We design PCB layouts and mechanics mainly when redesigning existing products and adapting designs for production.
NPI in five steps. Our NPI engineers work with the customer’s dedicated Program Manager. We run every introduction in five steps:
- Documentation and requirements review – we analyse the product specification and documentation and agree on acceptance criteria.
- Tooling and process preparation – we buy or build the tooling needed for assembly and inspection, prepare the process and write machine programs.
- Production setup and verification – we check programs, machine settings and soldering profiles, define detailed BOMs in the system and prepare operator instructions and production documentation.
- Customer acceptance – the customer reviews the prepared solutions and runs its own tests to confirm that the product and process are ready.
- Release to series production – production starts on a validated process with defined control points.
At every step we check that the process meets the customer’s requirements, most often defined in its specification, including the required IPC-A-610 class (2 or 3). If the customer requires it, we prepare PPAP documentation. Before the introduction we also carry out a P-FMEA, and we design solder paste stencils in IGI Gen Stencil software.
Inspection and test. Every board undergoes 100% 3D solder paste inspection (SPI) and 100% 3D automated optical inspection (AOI). Hidden joints, such as BGAs and QFN thermal pads, are verified by X-ray. We perform in-circuit testing (ICT), functional testing (FCT) and environmental testing in a climatic chamber. We design testers to the customer’s specification: we design and build tooling, fixtures and test stations in-house and write the test programs.
Feedback loop. After every NPI, the customer receives a technical report with findings and an action plan. Changes are implemented through a formal ECO process integrated with our ERP, and our MES provides traceability for every unit.
DFM and component availability. At Assel these are two separate analyses. DFM is carried out by an engineer who checks how the product can be assembled most easily and reliably. Component availability and lifecycle status are checked by purchasing at quotation and every re-quotation. Both perspectives reach the customer, so design decisions take into account both manufacturability and material risk.
How to prepare your data for a DFM review
The quality of a DFM analysis depends on the quality of the input data. When handing a design over to your EMS partner, provide:
- a complete manufacturing data package, preferably in an intelligent format (ODB++ or IPC-2581) rather than Gerber files only,
- a BOM with manufacturer part numbers (MPNs) and approved alternates,
- a pick-and-place file with reference designators and rotations,
- an assembly drawing with special requirements (coating, keep-out areas, torque values),
- the required IPC class and industry standards,
- test requirements: what must be detected and which functions verified,
- a volume forecast and the expected product lifecycle,
- information on which parts of the design are frozen (e.g. for certification reasons) and which can be changed.
The earlier this data reaches your EMS provider, the more changes will still be cheap. Send your design to the Assel team for review.
FAQ
What is a PCB DFM analysis?
It is a review of the printed circuit board design and assembly against the capabilities of a specific manufacturing process. It checks track and pad geometry, footprints, component placement, panelisation, test access and component availability, among other things, to eliminate problems before the first production run.
When is the best time for a DFM review?
As early as possible: already when planning component placement, and certainly before ordering prototype PCBs. A layout change costs a fraction of a new board revision after the pilot run.
Is DFM unnecessary if the designer knows the IPC standards?
IPC standards describe general rules. A DFM review by the EMS provider matches the design to the specific machines, materials and processes on which the product will be built, and to experience from similar projects.
What is the difference between DFM and DFT?
DFM checks whether the product can be manufactured and assembled. DFT checks whether it can be tested effectively: whether there are test points and programming access, and whether the chosen test strategy will detect typical defects.
How long does the NPI process take?
It depends on product complexity, material availability, the scope of tooling and testers, and the number of design iterations. A simple board and a complex device with electro-mechanical integration and a dedicated tester follow completely different schedules, so NPI lead time is best agreed individually based on the documentation.
Will a DFM analysis change my design without my approval?
No. The EMS provider prepares recommendations, and the design owner decides on every change. In regulated industries, changes go through a formal change control process.
What data should I send for a DFM analysis?
Ideally an ODB++ or IPC-2581 package, a BOM with manufacturer part numbers, a pick-and-place file, an assembly drawing, the required IPC class, test requirements and a volume forecast.
Sources
- Siemens – What is DFM and DFA (60–80% of cost determined by design decisions): https://blogs.sw.siemens.com/electronic-systems-design/2023/07/18/what-is-dfm-and-dfa/
- Leo AI – How Much Time Should Engineers Spend on DFM (rule of ten, design cost share): https://www.getleo.ai/blog/how-much-time-engineers-spend-dfm-2026
- Siemens – Streamlining NPI with PADS Professional Premium DFM (one in three projects delayed): https://blogs.sw.siemens.com/electronic-systems-design/2023/06/14/streamlining-npi-with-pads-professional-premium-dfm-and-pcbflow/
- Siemens – Smart design-to-manufacturing handover (2.7 re-spins per NPI): https://blogs.sw.siemens.com/electronic-systems-design/2021/08/25/smart-design-to-manufacturing-handover-with-online-pcb-dfm/
- Siemens – Xpedition design and manufacturing fact sheet (−57% re-spins): https://resources.sw.siemens.com/en-US/fact-sheet-xpedition-design-and-manufacturing
- Siemens – PCB design best practices: manufacturability verification (1,000+ rules): https://blogs.sw.siemens.com/electronic-systems-design/?p=9671
- Flux – PCB design review process (IPC-2221, footprints): https://flux.ai/p/blog/pcb-design-review-process
- Altium – Complete guide to DFM analysis: https://resources.altium.com/p/complete-guide-dfm-analysis
