Concept · Reliability & Quality
Special characteristic
A product or process characteristic that can affect safety, compliance with regulations, fit, function or later processing, marked for extra control through design, process planning and production.
- Also known as
- Critical characteristic, Key characteristic
- Type
- Concept
- Domain
- Reliability & Quality, Quality systems
Overview
Special characteristics are the features of a part or its process that matter most. They are identified by the customer, the supplier or both, marked with an agreed symbol, and carried through every quality planning document so that they receive extra attention.
How it works
A first list is drawn up during planning from customer requirements, earlier parts and risk analysis. The design FMEA and the process FMEA confirm or add to it, and each one is linked to a process step that controls it.
The control plan then states how each special characteristic is checked: the measurement method, the sample size and frequency, and the reaction when a result is out of limits. Capability studies and measurement system analysis focus on them, and they are often checked more tightly in production.
For a chip, examples include parameters tied to a safety function, a parameter the customer's system depends on, or a process step whose failure would not be caught by later tests.
Examples
- An output voltage accuracy used by a safety function in the customer's system.
- A wire bond pull strength marked for tighter sampling.
- A leakage current limit with a capability target in the control plan.
- A die attach void limit checked by X-ray on every lot.
Why it matters
Quality engineers, product engineers and customer quality engineers use special characteristics to decide where control effort goes. They run through every phase of APQP and are part of the evidence in a PPAP submission.
It matters most to: APQP and PPAP Engineer, Automotive Quality Engineer (IATF 16949), Customer Quality Engineer (Automotive), Product Engineer
Common confusions
- Not the same as Control plan
- The special characteristic is what must be controlled; the control plan says how it is checked and what to do when it fails.
Related standards
- IATF 16949 (automotive quality management system requirements)
Sources
- Special Characteristics (SC) (opens in a new tab), VDA QMC, 2026-11-10
- Special Characteristics in the Product Engineering Process (PEP) (opens in a new tab), VDA QMC, 2026-11-10
Related terms
Part of the Reliability & Quality glossary, with every term in the topic and the lifecycles, tools and standards that use them.
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Last reviewed . Written by The Semiconductor Hub editorial team. The full glossary