The Three Condition Types — Why They Exist
Every inspection criterion in IPC/WHMA-A-620E results in one of three possible condition classifications. These are not quality grades — they are inspection dispositions that tell the inspector, the Manufacturer, and the User exactly what action is required when a given characteristic is observed.
The standard assigns each condition type a single letter in the bracket notation system: A for Acceptable, D for Defect, P for Process Indicator, and N for No Requirement Established. Understanding the difference between these four is not optional — it is the foundation of every other inspection decision you will make.
Acceptable (A) — §1.5.1.1
An Acceptable condition is defined precisely in §1.5.1.1:
| Definition | A characteristic that indicates a condition that, while not necessarily perfect, will maintain the integrity and reliability of the assembly in its service environment. |
| Key principle | Acceptable does not mean perfect. It means fit for service. Cosmetic imperfections that do not affect function, reliability, or form are Acceptable. |
| Action required | None. The assembly passes. No documentation, no disposition, no rework. |
| Bracket code | A — appears as A1, A2, or A3 depending on which class(es) it applies to. |
The phrase "not necessarily perfect" is deliberate. IPC/WHMA-A-620 is an acceptability standard, not a perfection standard. An inspector who rejects a harness because it looks imperfect — when the condition is coded Acceptable — is not applying the standard correctly.
Defect (D) — §1.5.1.2
A Defect is a condition that fails to meet the acceptance criteria of the document or negatively affects the form, fit, or function of the assembly in its end-use environment.
| Definition | A condition that fails to meet the acceptance criteria of this document or negatively affects the form, fit, or function of the assembly in its end-use environment. |
| Manufacturer obligation | The Manufacturer shall [N1D2D3] document and disposition each defect. |
| Unique defects | It is the responsibility of the Manufacturer to identify defects unique to the assembly process. The User defines unique defect categories applicable to the product. |
| Bracket code | D — a [D1D2D3] condition is a defect for all three classes. A [N1D2D3] condition is only a defect for Class 2 and 3. |
Defect Hierarchy — The Inheritance Rule
A critical rule that many engineers misapply: a defect for a Class 1 product is also a defect for Class 2 and 3. A defect for a Class 2 product is also a defect for Class 3. The strictness only increases as the class number goes up — it never decreases.
This means: if you are inspecting a Class 2 assembly and the standard codes a condition as [D1D2D3], it is a defect regardless of class. If it is coded [N1D2D3], it is only a defect for Class 2 and 3 — Class 1 has no requirement for it.
Process Indicator (P) — §1.5.1.3
The Process Indicator is the most misunderstood condition type in IPC/WHMA-A-620E. The standard's definition is unambiguous, but it is routinely ignored in practice:
| Definition | A condition that identifies a characteristic that does not affect the form, fit, function, or reliability of a product. A process indicator is not a defect. |
| Cause | A result of material, design, and/or operator/machine related causes that create a condition that neither fully meets the acceptance criteria nor is a defect. |
| Disposition | Disposition of individual process indicators is not required. Affected product should be used as-is. |
| Not all PIs are specified | Not all process indicators are specified by this standard. The Manufacturer is responsible for identifying process indicators unique to their assembly process. |
| Bracket code | P — appears as P2 in [A1P2D3] meaning it is a Process Indicator for Class 2. |
What to Do With a Process Indicator
The standard is explicit: do not reject the assembly. Do not write a nonconformance report. Do not require rework. The individual assembly with a Process Indicator condition passes and goes to the customer.
What you must do is monitor Process Indicators as part of your process control system. The standard specifies the monitoring obligation precisely:
- If the number of process indicators signals an abnormal variation in the process — investigate
- If they identify an undesirable trend — act to reduce variation
- If they indicate the process is approaching out-of-control — analyze and take corrective action
A single process indicator is information. A pattern of process indicators is a process problem. The distinction is the entire basis of Statistical Process Control applied to harness assembly.
Conditions Not Specified — §1.5.1.4
Section 1.5.1.4 addresses what happens when the standard simply does not cover a particular condition. The rule is straightforward: conditions not specified are considered acceptable unless it can be established that the condition affects end user defined form, fit, function, or reliability.
This is the "silence equals acceptance" principle. If you cannot find an applicable acceptance criterion in IPC/WHMA-A-620E, the condition passes — unless you have documented engineering evidence that it affects the product's performance. The burden of proof for rejection falls on the person rejecting, not the person accepting.
Reading Bracket Notation — Practical Guide
Every requirement in IPC/WHMA-A-620E uses bracket notation to communicate all three class conditions simultaneously. The format is always: [Class 1 condition / Class 2 condition / Class 3 condition].
| Notation | Meaning | Action for Class 2 assembly |
|---|---|---|
| [A1A2A3] | Acceptable for all three classes | Pass — no action required |
| [A1P2D3] | Acceptable Cl.1 / Process Indicator Cl.2 / Defect Cl.3 | Pass the assembly — monitor the process |
| [A1A2D3] | Acceptable Cl.1 and 2 / Defect Cl.3 only | Pass — no action required |
| [N1D2D3] | No requirement Cl.1 / Defect Cl.2 and 3 | Reject — document and disposition |
| [D1D2D3] | Defect for all three classes | Reject — document and disposition |
| [N1N2D3] | No requirement Cl.1 and 2 / Defect Cl.3 only | Pass — only a defect for Class 3 |
| [N1A2D3] | No req. Cl.1 / Acceptable Cl.2 / Defect Cl.3 | Pass — condition is acceptable for Class 2 |
Process Control and Condition Monitoring — §1.6
Section 1.6 ties the condition type system directly to the broader quality management framework. The primary goal of process control is to continually reduce variation in processes, products, or services to provide products meeting or exceeding customer requirements.
Class 3 Process Control Requirement
Class 3 assemblies have a specific obligation: Class 3 shall [N1N2D3] develop and implement a documented process control system. If such a system is established, it shall [N1D2D3] define process control and corrective action limits. This means Class 3 manufacturers do not have a choice — a documented process control system is mandatory.
For Class 1 and 2, process control methodology shall [N1D2D3] be used in the planning, implementation, and evaluation of manufacturing processes. The methodology does not have to be a formal SPC system, but the intent to control and evaluate process capability is required.
100% Inspection Default
Without a documented process control plan that specifies sampling inspection, manufacturers shall [N1D2D3] perform 100% inspection. This is a critical point that is frequently overlooked in supplier qualification. If your purchase order does not reference a documented sampling inspection plan, your supplier is obligated to inspect every unit. Verify this before accepting a delivery inspection report that references sampling.
Statistical Process Control — §1.6.1
When a Statistical Process Control system is used, it shall [D1D2D3] include seven mandatory elements:
- Training: Personnel with assigned SPC responsibilities receive training commensurate with their role in development, implementation, and utilization
- Quantitative methodology: Evidence maintained to demonstrate process capability and control. Improvement strategies define initial process control limits
- Sampling criteria: Criteria for switching to sample-based inspection defined. Criteria for reversion to higher inspection levels (up to 100%) when processes exceed control limits also defined
- Lot containment: When defects are identified in a sample lot and exceed the sampling plan limit, the entire lot is 100% inspected for that defect type
- Corrective action system: System in place to initiate corrective action for process indicators, out-of-control processes, and discrepant assemblies
- Audit plan: Documented audit plan to monitor process characteristics and/or output at a prescribed frequency
- Objective evidence: Evidence of process control may be control charts or other SPC tools derived from process parameter and/or product parameter data
How the Three Conditions Connect to Process Control
The three condition types and the process control system are designed to work together. Here is how they interact in a functioning quality program:
Summary — The Rules in Plain Language
- Acceptable: Not necessarily perfect — but fit for service. Pass. No action.
- Defect: Fails acceptance criteria or affects form, fit, function. Reject. Document and disposition every defect.
- Process Indicator: Not a defect. Pass the assembly. Monitor the process. Act on patterns, not individual occurrences.
- Not Specified: Acceptable by default unless you can prove it affects the product.
- Defect inheritance: Class 1 defects are defects for Class 2 and 3. Class 2 defects are defects for Class 3. Strictness only goes up.
- 100% inspection default: Without a documented sampling plan, inspect every unit.
- SPC is optional — but all-or-nothing: If you implement SPC, all seven §1.6.1 elements are mandatory.
- Class 3 mandatory: A documented process control system is required for Class 3. No exceptions.
Les trois types de conditions — pourquoi ils existent
Chaque critère d'inspection dans IPC/WHMA-A-620E aboutit à l'une des trois classifications de conditions possibles. Ce ne sont pas des notes de qualité — ce sont des dispositions d'inspection qui indiquent exactement l'action requise lorsqu'une caractéristique donnée est observée.
Acceptable (A) — §1.5.1.1
Une condition Acceptable indique une caractéristique qui, bien que pas nécessairement parfaite, maintiendra l'intégrité et la fiabilité de l'assemblage dans son environnement de service. Acceptable ne signifie pas parfait — cela signifie apte au service. Aucune action requise.
Défaut (D) — §1.5.1.2
Un défaut est une condition qui ne satisfait pas aux critères d'acceptation ou qui affecte négativement la forme, l'aptitude à l'emploi ou la fonction de l'assemblage dans son environnement d'utilisation finale.
Le fabricant shall [N1D2D3] documenter et dispositionner chaque défaut. Les options de disposition incluent : retouche, utilisation en l'état (nécessite l'accord de l'utilisateur pour les Classes 2/3), mise au rebut ou réparation (nécessite l'accord de l'utilisateur pour la Classe 3).
Règle d'héritage des défauts
Un défaut pour un produit de Classe 1 est automatiquement un défaut pour les Classes 2 et 3. Un défaut pour la Classe 2 est un défaut pour la Classe 3. La rigueur ne fait qu'augmenter avec le numéro de classe — jamais diminuer.
Indicateur de processus (P) — §1.5.1.3
Un indicateur de processus est une condition qui n'affecte pas la forme, l'aptitude à l'emploi, la fonction ou la fiabilité d'un produit. Un indicateur de processus n'est pas un défaut.
La disposition des indicateurs de processus individuels n'est pas requise. Le produit affecté doit être utilisé en l'état. Ce qui est requis, c'est la surveillance des indicateurs de processus dans le cadre du système de contrôle de processus.
Lecture de la notation entre crochets
| Notation | Signification | Action pour assemblage Classe 2 |
|---|---|---|
| [A1A2A3] | Acceptable pour les trois classes | Passe — aucune action requise |
| [A1P2D3] | Acceptable Cl.1 / Indicateur Cl.2 / Défaut Cl.3 | Passe — surveiller le processus |
| [N1D2D3] | Pas d'exigence Cl.1 / Défaut Cl.2 et 3 | Rejeter — documenter et dispositionner |
| [D1D2D3] | Défaut pour les trois classes | Rejeter — documenter et dispositionner |
| [N1N2D3] | Pas d'exigence Cl.1 et 2 / Défaut Cl.3 seulement | Passe — uniquement un défaut pour la Classe 3 |
Contrôle de processus — §1.6
L'objectif principal du contrôle de processus est de réduire continuellement la variation dans les processus, produits ou services pour fournir des produits répondant aux exigences des clients.
La Classe 3 shall [N1N2D3] développer et mettre en œuvre un système de contrôle de processus documenté — c'est obligatoire, sans exception. Pour les Classes 1 et 2, la méthodologie de contrôle de processus doit être utilisée dans la planification et l'évaluation des processus de fabrication.
Sans un plan d'inspection par échantillonnage documenté, les fabricants shall [N1D2D3] effectuer une inspection à 100%. Si votre bon de commande ne référence pas un plan d'échantillonnage documenté, votre fournisseur est obligé d'inspecter chaque unité.
Résumé — Les règles en langage clair
- Acceptable : Pas nécessairement parfait — mais apte au service. Passe. Aucune action.
- Défaut : Ne satisfait pas aux critères. Rejeter. Documenter et dispositionner chaque défaut.
- Indicateur de processus : Pas un défaut. L'assemblage passe. Surveiller le processus. Agir sur les tendances, pas les occurrences individuelles.
- Non spécifié : Acceptable par défaut sauf preuve d'impact sur la forme, l'aptitude ou la fonction.
- Inspection à 100% par défaut : Sans plan d'échantillonnage documenté, inspecter chaque unité.
- SPC optionnel mais complet : Si vous mettez en œuvre le SPC, les 7 éléments du §1.6.1 sont obligatoires.
- Classe 3 obligatoire : Un système de contrôle de processus documenté est requis. Pas d'exceptions.
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