PVT is a stage in the NPI process. During PVT, no further design changes are expected. You are focused on working out the final kinks in the manufacturing process before entering Mass Production. The goal of the engineering team is to produce one “golden line” that operates with desired yield and throughput. This golden line can then be replicated by the operations teams to scale up production.
Qualities of PVT
- Volumes are typically 5-10% of the initial mass-production run.
- Production-intent processes and parts are in place.
- Custom tooled parts are used: no more milling, printing, soft molds, etc.
- Some tools and processes may be introduced at PVT; they are in effect being qualified before entering mass production.
- In practice, there may still be some experiments going on at PVT, but this is not the ideal situation and you should strive to avoid it.
- The units that are built at PVT are revenue-able (can be sold to customers).
- If this is not the case, you’re not ready for PVT, but having a DVT build.
- The focus is on improving yield and throughput to hit mass production goals
- The build will often start “slow” and speed up while moving through gated phases (‘red’, ‘yellow’, ‘green’ being common phase descriptors) that reflect operator training level, throughput, and yield levels.
- Test station software and manufacturing firmware are improved to reduce retest rates and cycle time.
- Process flaws are addressed to improve yield and throughput.
- Cosmetic fallout caused by activities on the manufacturing line is addressed.
- PVT is often heavily focused on cosmetic yield.
- The packaging flow is perfected.
- Outgoing Quality Control (OQC) and/or Final Quality Control (FQC) processes roll out in force.
- Proceeding into the next PVT build phase (or on to Ramp and Mass Production) is often gated by a problematic vendor or three, whether due to yield problems, insufficient build quantities, late deliveries, or other problems.
Uses of PVT Units
PVT units are used for:
- Sale
- Units at this stage should ideally be “revenue-able” – able to be sold to customers.
- Often, cosmetic flaws are the reason that units from PVT will not be sold. You can still use these for other purposes. If not terribly egregious, you can offer them to friends and family at a significant discount.
- Internal development
- Beta testing
- “Golden units” (ideal devices) are used for GR&R activities, test station validation, and manufacturing firmware validation at the CM
NPI Process Flow
- The PVT stage begins after DVT has been completed with:
- Sufficient confidence in addressing yield loss issues
- Certifications have been completed
- Packaging is ready
- Reliability and environmental testing show acceptable results
- A significant change in the design at the PVT stage should move the product back to DVT. In practice, you are more likely to see “Pre-PVT” or “PVT-2” builds than a reset to DVT.
- PVT is completed when:
- There are acceptable yields and throughput for mass production on at least one manufacturing line (the “golden line”, which will be replicated to other lines).
- You have sufficient build material in house and on the way to manufacture the desired number of devices.
- After the PVT stage is completed, production begins to ramp to Mass Production levels.
Related Concepts
- Manufacturing Test and Manufacturing Firmware are heavily hammered to improve reliability and speed during PVT
- Outgoing Quality Control (OQC)
- Final Quality Control (FQC
References
- Hardware engineers speak in code: EVT, DVT, PVT decoded by Anna-Katrina Shedletsky
PVT is the “last build” — the units you are building are supposedly intended to be sold to customers, if they pass all of your test stations. PVT typically transitions directly into Ramp and Mass Production, or a Pilot build with no time gap.
Purpose: to verify mass production yields at mass production speeds
- Validate and qualify additional tools needed to support quantities for early ramp
- No parallel experimental units allowed (I have never seen this actually happen, but it is a goal that should be driven to for as long as possible)
Typical Quantities: 1K to 20K
- All units are intended to be sold to customers
- The build is potentially phased — red, yellow, green is common — indicating “maturity” of the production process, which includes a combination of operator training level, line speed, and line yield
Things that Go Wrong:
- There is almost always at least one issue that is still outstanding at the start of PVT — this is likely the item at highest risk of impacting your schedule
- There is usually at least one vendor whose yields are way lower than expected, and because they cannot produce at the quantities promised, input is gated by their deliveries
- If you have a high cosmetic standard, your cosmetic yield likely starts at 0%. Unless you decide to loosen your standard, the conventional way to improve it is to knowingly input units to a 0% yield line and painstakingly seek places where damage occurs and improve them. This process can take weeks and hundreds or thousands of units. An Instrumental system can streamline and significantly accelerate this process
Exit Criteria: mass production yields at mass production speeds on at least one line, and replication to other lines already started.
- The different engineering validation stages in a nutshell | EVT, DVT, PVT | by Chris Boucher | Medium
- Overview of the hardware product development stages: POC – EVT – DVT – PVT explained
- PVT objectives:
- Verify mass-production yields;
- Finalize DF-X with the help of CM aiming to minimize waste and make assembly more efficient;
- Make the first pilot production run and ensure the product quality adheres to your expectations;
- Weed out the last design flaws during the pilot production run;
- PVT prototype quantities typically range between 50 and 500 in order to verify mass-production yields and provide product samples.
- Technologies: Industrial technologies suitable for volume production only;
- Outputs / Deliverables: Final product produced in a limited quantity by using the tools for mass-production. Electronic layouts and components are revisited using PCB stencils for soldering components. Mechanical DFM is finalized and plastic parts are manufactured by using 2nd generation moulds.
- Duration: 3-6 months in general.
- Limitations: The time required to design and produce custom tools is generally long.
- PVT objectives:
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