A component goes on allocation, the factory offers an alternative, and the question arrives: does this need retesting? The answer depends on whether the alternate was qualified in advance or introduced under pressure. A policy exists to make that decision routine rather than urgent.
This guide is part of our Charger Quality & Inspection. Read the full topic guide for the decisions that come before and after this step.
Why “we have alternatives” is not a policy
Listing two suppliers in a BOM does not create resilience. A second source is only real if the alternate part has been evaluated, if its electrical and thermal behaviour has been verified in the product, if the relevant documentation has been updated, and if the factory has agreed when it may be substituted. Without those four conditions, the alternate is a possibility, not a plan.
The components that actually cause line stops
Not every part deserves dual qualification. The candidates are the long-lead, single-source and allocation-prone items: the primary controller, the power switch, the transformer or magnetics, the output capacitors, the connector family and, for wireless products, the coil assembly and the wireless controller. A common resistor or capacitor from a mature family rarely justifies the qualification cost.
Qualification: what an alternate part must pass
| Check | Purpose | Evidence |
|---|---|---|
| Electrical equivalence | Ratings, tolerances, behaviour under load | Datasheet comparison and bench test |
| Thermal verification | Temperature rise in the actual enclosure | Load test with thermocouples |
| EMC pre-scan | Switching behaviour change | Pre-compliance scan report |
| Reliability review | Derating, life, supplier quality history | Supplier data and field record |
The depth of the check scales with the role of the component. A controller substitution is closer to a new design than a capacitor substitution, and should be treated accordingly.
Keeping alternates approved over time
Approval decays. A supplier changes a die, a factory changes a process, and a previously qualified alternate may no longer be the same part. The policy should include a periodic review, a requirement for the supplier to notify changes, and a re-verification trigger when a change is declared. Alternates that were qualified two years ago and never re-checked are a latent risk.
Change notification and approval flow
The flow should be explicit: the factory proposes a change, the customer reviews the impact, the customer approves in writing, the change is recorded in the product file, and the approved sample is updated where relevant. The critical element is the written approval. A substitution made between the pilot and the bulk run without notification invalidates the assumption the customer’s certification and warranty are based on.
Cost of dual qualification versus cost of a stop
Qualifying an alternate costs engineering time, test time and documentation. A line stop costs the same engineering time under pressure, plus expedited freight, plus a possible launch delay, plus the risk of an unqualified substitution. For a component with a long lead time or a single supplier, the qualification cost is usually the cheaper of the two outcomes and the more predictable.
Contract language for component changes
- No substitution of safety-critical or certified components without written approval
- Notification within a stated period of any supplier or process change
- Customer approval required before shipment of units built with a substituted part
- Records of the substitution retained with the product file
- Cost of re-verification allocated according to the origin of the change
What buyers should ask in the RFQ
- Which components are single-sourced, and what is the lead time for each?
- Which alternates have already been qualified and tested?
- How is a component change notified and approved?
- What is the re-verification process when an alternate is introduced?
- Which components would require retesting of the certification file?
Second-source policy template
- Critical component list with lead time and supplier count
- Qualification status for each alternate
- Verification evidence required by component class
- Notification and written approval flow
- Re-verification trigger and review cadence
- Documentation update procedure
Testing the policy before a crisis
A second-source policy is only credible if it has been exercised. The practical test is a tabletop exercise: choose a critical component, assume the primary supplier cannot deliver for eight weeks, and walk through what would actually happen. Which alternate would be used? Is it qualified? Who approves the substitution? Which documents change? How long would re-verification take? The answers usually reveal one or two gaps – an alternate that was never tested in the enclosure, or a change-notification path that exists only in the quality manual. Running the exercise during a quiet period takes an afternoon; running it during an allocation crisis takes the same afternoon plus the cost of expedited freight and a possible delay. Programs that treat the exercise as part of annual supplier review tend to be the ones that absorb a supply shock without moving a launch date.
FAQs
Should a charger BOM have second sources for every part?
No. Dual qualification should focus on long-lead, single-source and allocation-prone components. Applying it to every commodity part adds cost without reducing the risk that actually stops a line.
Who approves an alternate component?
The customer approves changes affecting certified or safety-critical parts, in writing. The factory may approve lower-risk commodity substitutions within an agreed framework, provided the change is recorded and reported.
Does changing a component affect certification?
It can, particularly where the component affects electromagnetic behaviour, thermal margins or safety-related spacing. The test house should be consulted before a substitution is implemented on a certified platform.
Next step
Wecent Group maintains platform-based BOMs with qualified alternates for long-lead components and a documented change-notification process. Send your component risk questions to the contact page. Related reading: quality control, OEM/ODM manufacturing, OEM project sequence and RFQ template. External references: ISO 9001, IEC standards, ECHA REACH, EU RoHS directive, UL and FCC equipment authorisation.
More on this topic: wireless charger manufacturing and GaN chargers from 20W to 240W, wireless charging on phones, Qi2 chargers explained.