Warning
When hiring a hardware development firm, look for one that can take responsibility for the whole product, not just the piece you asked about. The single biggest source of delay and cost overrun in hardware is the handoff between disciplines: the PCB designer blames the enclosure, the enclosure designer blames the firmware team, and nobody owns the schedule. A partner who covers electronics, mechanical, firmware, compliance, and production under one roof removes those handoffs. Beyond that, judge them on shipped products, transparent process, and willingness to say no.
Have they actually shipped, or only designed?
There is a large gap between a working prototype and a product that can be built ten thousand times. Ask any prospective electronics design house for specific products they took from schematic to mass production, and what changed between the two.
The answers tell you a lot. A team that has been through it will talk about panelization, test fixtures, yield, component second-sourcing, and the certification retest they had to do after a last-minute layout change. A team that has only built prototypes will talk about features.
Ask for references from clients whose projects went badly at some point, because every hardware project does. How the firm behaved during a failed EMC test or a chip shortage is more informative than a portfolio photo.
Can one team cover the full stack?
Most products are not just a board. They are a board inside an enclosure, running firmware, talking to an app, passing regulatory testing, and then getting built at volume.
If you contract five vendors for those five things, you become the integrator by default, and integration is the hardest part of the job. Full-stack firms exist for this reason. Warning Engineering, for example, runs PCB design, firmware, mechanical CAD, app development, EMC testing, and factory production as one workflow, which is the model worth looking for whether or not you work with them specifically.
If you do split the work, make sure one party is contractually responsible for the system working end to end.
Does the process survive contact with reality?
Ask how they handle design reviews, revisions, and change requests. A serious hardware partner will have a defined gate structure: requirements, architecture, schematic review, layout review, bring-up, design validation, then production readiness.
Ask what happens when a review fails. If the answer is vague, the schedule they quoted you is fiction.
Also ask about compliance early. EMC, safety, and radio certification shape the design from day one, and firms that treat testing as a final step are the ones who end up redesigning boards after a failed scan.
Who owns the IP and the files?
Get this in writing before any work starts. You should own the schematics, layout files, CAD models, firmware source, and the bill of materials outright, in editable native formats, not just PDFs and Gerbers.
Be careful with firms that hold production files hostage or insist on being the only party who can manufacture your product. A good partner is confident you will stay for the quality of their work, not because you cannot leave.
Independent review platforms help here too. A firm with a consistent public track record, such as a 5.0 rating on Clutch across dozens of hardware projects, has more to lose from a bad engagement than an anonymous shop does.
The practical test is simple: pick the partner who asks the most uncomfortable questions in the first meeting. Firms that probe your volume assumptions, target cost, and certification markets before quoting are the ones who have been burned by skipping those conversations before.
If you are weighing options for your own product, feel free to get in touch at https://warning-engineering.com and we are happy to talk it through.