Why the Class Decision Comes Before Everything Else
The acceptance class determines your connector seal materials, conductor fill percentage, allowable strand damage, crimp bellmouth requirements — and every other acceptance criterion in IPC/WHMA-A-620E. Getting it wrong before you start costs money in rework, creates re-inspection cycles, and can result in field failures.
The Three Classes — Exact Definitions
IPC/WHMA-A-620E Section 1.3 defines three product classes based on intended end-use environment, not workmanship quality.
Class 1 — General Electronic Products
Includes products suitable for applications where the major requirement is the function of the completed assembly. Cosmetic imperfections are acceptable as long as the assembly functions. Use for: interior cab controls, non-critical lighting, short-lifecycle prototypes.
Class 2 — Dedicated Service Electronic Products
Includes products where continued performance and extended life is required, and for which uninterrupted service is desired but not critical. The end-use environment would not typically cause failures. Use for: engine control harnesses, transmission, hydraulic valve control, instrument clusters, CAN bus wiring.
Class 3 — High Performance / Harsh Environment
Includes products where continued performance is critical, equipment downtime cannot be tolerated, and the end-use environment may be uncommonly harsh. Use for: fire suppression circuits, ROPS/FOPS interlocks, underground mining vehicle controls, remote-site equipment where service access is dangerous.
| Class | Official Name | Heavy Equipment Default | IPC Notation |
|---|---|---|---|
| Class 1 | General Electronic Products | Non-critical interior systems | A1 / N1 |
| Class 2 | Dedicated Service | Most vehicle electrical systems | A2 / P2 |
| Class 3 | High Performance / Harsh Env. | Safety-critical only | D3 |
Step-by-Step Selection Framework
Work through these questions in order. The first "Yes" determines the class.
Documenting the Class on Engineering Drawings
The class must appear on the drawing title block before production begins. Reference the revision letter — never write "IPC/WHMA-A-620" without it.
ACCEPTANCE STANDARD : IPC/WHMA-A-620E
ACCEPTANCE CLASS : CLASS 2
REVISION : REV A — 2025-06-05
DRAWN BY : LoomWire EngineeringPourquoi la décision de classe vient avant tout le reste
La classe d'acceptation détermine les matériaux de joint de connecteur, le pourcentage de remplissage du conducteur, les dommages admissibles aux torons et les exigences de cloche de sertissage. Se tromper avant de commencer la conception coûte de l'argent en retouches et peut entraîner des défaillances terrain.
Les trois classes — définitions exactes
Classe 1 — Produits électroniques généraux
Comprend les produits adaptés aux applications où la principale exigence est la fonction de l'assemblage terminé. Usage : commandes de confort de cabine, éclairage non critique, prototypes à courte durée de vie.
Classe 2 — Produits électroniques à service dédié
Comprend les produits où une performance continue et une longue durée de vie sont requises. Usage : faisceaux de contrôle moteur, transmission, commande hydraulique, tableaux de bord, bus CAN.
Classe 3 — Haute performance / environnement sévère
Comprend les produits où la performance continue est critique et les arrêts inacceptables. Usage : suppression d'incendie, verrouillages ROPS/FOPS, commandes de véhicules miniers souterrains.
Need the right class on every drawing? Besoin de la bonne classe sur chaque dessin ?
LoomWire specifies the class, revision, and inspection method on every engineering package we deliver. No ambiguity for your fabricator or your auditor. LoomWire spécifie la classe, la révision et la méthode d'inspection sur chaque package d'ingénierie. Aucune ambiguïté pour votre fabricant ou votre auditeur.