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How to Choose a Contract Manufacturer: The 15-Question Audit
How to choose a contract manufacturer: a 15-question audit covering fit, quality, engineering, supply chain and terms, with what a good answer looks like.
by the HardwareMap editors4 min read
Contents
How to choose a contract manufacturer comes down to evidence: ask every candidate the same questions, require proof, and score the answers side by side. The 15 questions below are the audit, grouped by fit, quality, engineering, supply chain and terms. Print it, send it with your request for quote, and use it on the factory floor. It belongs to our electronics contract manufacturer guide.
Before the audit: shortlist on fit
Do not audit everyone. Shortlist three to five candidates whose typical program size, technology and certifications match yours, then send each the same RFQ package. Our PCB assembly guide lists what that package contains. If you are still on prototypes, an online assembler is likely enough for now; the prototype to production note covers when to make the move.
How to choose a contract manufacturer: the 15 questions
Fit
- What is your typical program size, and where would ours rank? You want a CM where your program matters. Ask what share of revenue its largest and smallest customers represent.
- Who will own our program, by name? A named program manager and a named NPI engineer. Meet both before signing.
- What products like ours have you built? Ask for a reference customer with similar complexity and call them.
Quality
- Which certifications do you hold, for which sites? ISO 9001 at minimum. ISO 13485 for medical, AS9100 for aerospace, ITAR registration for defense articles, as your market requires. Check each certificate's scope and site with the issuing body; the IAF CertSearch database covers many accredited certificates.
- Which IPC-A-610 class do you build to by default, and are inspectors IPC-certified? Workmanship standards come from IPC (IPC standards). A good answer names the class and shows training records.
- What is your first-pass yield on similar products, and how do you report it? Ask for a sample yield report. A CM that cannot show one does not measure it.
- Walk me through your last corrective action. A good answer is specific: the defect, the root cause, the fix, the verification. Vague answers mean a weak quality system.
Engineering
- What does your DFM review include, and what will you send back? Ask for a sample DFM report from another customer, anonymized.
- What inspection and test equipment do you have in-house? SPI, AOI, X-ray, flying probe, ICT, functional test stations. Anything subcontracted adds lead time and risk.
- Who builds and owns test fixtures? Clarify design, cost, ownership and what happens to fixtures if you leave.
Supply chain
- How do you buy components, and from whom? Authorized distributors and manufacturers are the baseline. Ask how they handle broker purchases during shortages and how they screen for counterfeits.
- What traceability do you keep? Lot codes per board, per reel, linked to serial numbers. If a part lot goes bad, can they find every affected unit?
- How do you handle substitutions and end-of-life notices? Substitutions should need your written approval. Ask how far ahead they flag parts going obsolete.
Terms
- What is our liability for inventory if forecasts change? The cancellation window, non-cancellable and non-returnable parts, and excess stock. This is the clause that hurts startups most.
- How would we leave? Notice period, return of tooling, fixtures and consigned parts, and transfer of process documentation. A CM confident in its service will answer this plainly.
Scoring the answers
Score each question 0, 1 or 2: no answer or evasive; an answer without evidence; an answer with evidence. Maximum 30.
Do not let price decide alone. A CM that scores well and quotes higher than the cheapest one is often the cheaper partner over the life of the product, because rework, delays and a forced move cost more than a few percent on the board.
After you choose: the first build
Signing is the start of the audit, not the end. The first build shows whether the answers were true.
- Run a pilot build first. A small lot, often tens to a few hundred units, built on the production line with production test. Treat it as part of the audit.
- Require a first-article inspection report. One unit checked against the BOM, drawings and test spec before the lot proceeds.
- Ask for the build data. Yield by station, defect Pareto, AOI and X-ray results, rework log. Compare against what the CM said in question 6.
- Hold a build review. Walk through every defect with the NPI engineer. Agree on fixes for the design and for the process, with owners and dates.
- Re-score. Update the scorecard with what the pilot showed. If the score drops sharply, it is cheaper to move now than after tooling and fixtures multiply.
Red flags during the audit
- No named program owner, or a sales contact who answers every engineering question.
- Certificates that cover a different site from the one that would build your product.
- No yield data, or yield data only as a single headline number.
- Reluctance to show the floor, the stores area or the moisture-sensitive parts storage.
- Unclear answers on inventory liability or exit.
Bring counsel into the contract review; the agreement terms behind questions 14 and 15 are legal documents, not checkboxes.
Frequently asked questions
How many contract manufacturers should I talk to?
Three to five is a common working range. Fewer gives you no comparison on price, responsiveness or engineering depth. More consumes weeks of your team's time on quotes and calls. Shortlist on fit first, volume, technology and certifications, then send the same request for quote package to each, and visit the top two before deciding.
Should I visit a contract manufacturer before signing?
Yes, if at all possible. A site visit shows things a quote cannot: housekeeping, how moisture-sensitive parts are stored, whether operators follow work instructions, and how engineers talk about problems. Ask to walk the line that would build your product and to meet the program manager and engineer who would own it. If a visit is impossible, ask for a recorded walk-through.
How do I verify a contract manufacturer's certifications?
Ask for the certificate, then check it with the certification body named on it. For accredited ISO certifications, the IAF CertSearch database lets you look up many certificates by company. Check the scope and the site address: a certificate may cover one facility but not the one that would build your product. For ITAR, ask for the registration status.
What should be in a request for quote to a contract manufacturer?
Send the full data package: Gerbers or ODB++, fabrication and assembly drawings, a bill of materials with manufacturer part numbers and alternates, centroid files, test requirements, mechanical drawings for box build, and annual volume forecasts by year. Include target dates and the quality standard you expect. Identical packages make quotes comparable.
HardwareMap catalogues the startups that made it through this audit and into production. Building one? Submit it and get a part number.
Building one?
Submit it to the index and get a part number. Every entry is reviewed by hand.