Is AOI enough to guarantee quality?

AOI is a strong checkpoint for placement and soldering defects, but it works on what the process produced. Process control upstream, including materials, printing and placement parameters, determines how much there is for AOI to catch.

Should I approve volume production from a sample alone?

A sample confirms the design; it does not by itself confirm batch-to-batch consistency. Ask which process checkpoints apply to volume runs and how the results are recorded.

What is the biggest quality risk in flexible circuits?

In practice, the areas around bending and connectors: coverlay alignment, stiffener bonding and gold finger condition. These also appear earliest in field use, which is why they are worth inspecting on the first sample.

How do I raise a specific requirement?

State it in your RFQ, for example a particular inspection point, packing requirement or drawing tolerance. Requirements raised before production become part of the confirmed construction.

Home/Flexible PCB Quality Verification

How to Verify Flexible PCB Quality Before Volume Production

A prototype that passes functional testing does not automatically mean the volume build will. Flexible circuits have failure modes that only appear under specific conditions, and most are visible long before a customer complaint.

1. Design data review, before anything is built

Verification starts with the data, not the board. A manufacturing review checks layer arrangement and whether the stackup matches the intended bend behaviour; coverlay openings so that pads, connector fingers and test points stay exposed; stiffener placement against the actual connector and assembly forces; bend areas and whether routing crosses them in a way that would fail under repeated flexing; and panelisation, so assembly and singulation do not damage the flex areas.

Issues found at this stage cost nothing to fix. The same issues found after tooling or assembly cost both money and schedule.

2. Sample inspection (first article)

When the sample arrives, inspect it against the drawing rather than against expectations. The checks that most often reveal problems are:

Outline dimensions and hole positions, which determine whether the part fits the assembly at all.
Circuit continuity and isolation, confirming electrical function before anything else.
Coverlay alignment and openings, since misalignment blocks soldering or connector insertion.
Stiffener bond and position, which cause connector and assembly failures when weak or offset.
Gold finger appearance and dimensions, affecting insertion cycles and contact reliability.
Bend area condition, where cracks or stress marks predict early field failure.
Marking and part identification, needed for traceability if a problem appears later.

3. Process checkpoints in production

Once the design is confirmed, quality is maintained by process control rather than final inspection alone. Production follows a defined sequence: incoming inspection, solder paste printing, high-speed placement, reflow soldering, AOI automated optical inspection, and packing and shipping.

Two points matter especially for flexible circuits. Incoming inspection matters because flexible materials such as base film, adhesive, coverlay and stiffener vary between batches, and problems there cannot be corrected later in the process. AOI catches placement and soldering defects before packing, but it does not replace a defined, repeatable process upstream.

Questions to ask your supplier

Is the construction confirmed with me in writing before production starts?
Which inspection points exist in your process, and what is checked at each one?
How are flexible-specific risks handled, including coverlay alignment, stiffener bonding and bend areas?
If a defect is found after shipment, what traceability exists (batch, date, panel)?
Can I receive samples before releasing volume, and what changes between sample and volume?

What to record for traceability

Keep, for each order: the confirmed construction including stackup and notes, the sample inspection result, the order and batch details, and any deviation approved during production. When a problem appears months later, this record is what makes it solvable rather than a discussion.

How this applies at Fanjuda

Production follows the published sequence above, and the construction is confirmed with the customer before production starts. Full details are on the Quality Control page. For the product scope this applies to, see Flexible PCB (FPC); for sample-stage verification see the FPC prototype service page; to discuss a specific quality requirement, use the inquiry form on the contact page.

Frequently Asked Questions

Is AOI enough to guarantee quality?: AOI is a strong checkpoint for placement and soldering defects, but it works on what the process produced. Process control upstream, including materials, printing and placement parameters, determines how much there is for AOI to catch.
Should I approve volume production from a sample alone?: A sample confirms the design; it does not by itself confirm batch-to-batch consistency. Ask which process checkpoints apply to volume runs and how the results are recorded.
What is the biggest quality risk in flexible circuits?: In practice, the areas around bending and connectors: coverlay alignment, stiffener bonding and gold finger condition. These also appear earliest in field use, which is why they are worth inspecting on the first sample.
How do I raise a specific requirement?: State it in your RFQ, for example a particular inspection point, packing requirement or drawing tolerance. Requirements raised before production become part of the confirmed construction.

Discuss your quality requirements

Contact us with your project requirements through the contact page. Our team will explain how to submit Gerber files securely for review, then confirm production feasibility, lead time and quotation.