INSPECT COMMON PCB ISSUES

This Gold Phoenix PCB Knowledge Center article explains key points for inspecting common printed circuit board quality concerns.

As our world continues to evolve toward online buying markets for goods of all kinds, online purchasing options are greater than ever — but this comes with potential trade‑offs. You may have noticed that in some situations, delivered quality fails to match expectations set during online procurement. Some PCB quality issues can be easily identified, while others are difficult to detect.

Solder Mask

Cosmetic characteristics are among the easiest PCB attributes to verify against ordered requirements. Each printed circuit board has unique properties. Solder mask is available in multiple colors; white, red, blue, black, and green are the most common options provided by PCB manufacturing services. Solder mask can be finished as either glossy or matte.

Inspect both sides of the board to quickly confirm whether solder‑mask coverage is single‑sided or double‑sided, and validate alignment with ordering specifications.

Certain coating‑related properties cannot be judged by visual observation alone. These include the solder‑mask material type, availability of certification documents listing mask type, lot code and date code, and whether one or two coating layers have been applied. Some PCBs require two coats of solder mask, while others only need one. This detail cannot be distinguished by naked‑eye viewing and requires magnification tools.

During production workflows, a second solder‑mask coat may be applied to resolve coating or registration defects. Magnification instruments, microscopes, or handheld eye‑loops allow inspectors to confirm if dual‑coat processing has taken place. In many scenarios, the number of solder‑mask coats will not affect overall PCB quality. However, where critical component heights demand strict clearance requirements, excessive solder‑mask thickness may create serious assembly‑related problems.

Legend, also known as silkscreen, is another visually identifiable PCB feature. Common silkscreen colors include white, black, and yellow. Red and blue are also available selections; white is the most frequently supplied color for online‑ordered PCBs. Confirm that delivered silkscreen matches requirements documented in project files.

Surface finish represents another externally observable characteristic. Available surface‑finish types include hot air solder leveled (HASL), ENIG, immersion gold, immersion silver, lead‑free HASL, OSP, and hard gold. While surface color offers preliminary clues about finish type, visual inspection alone cannot guarantee the delivered finish conforms to ordered specifications.

Surface Finish

Validating surface finish is more complex than checking solder‑mask and silkscreen colors. Visual appearance can be misleading: a surface that looks like standard HASL may actually be lead‑free HASL. Immersion silver and immersion tin show similar surface appearances, whereas immersion gold displays a distinct gold‑toned surface.

Different surface finishes require matching assembly process parameters. Mismatched surface finish will halt assembly work, forcing either re‑fabrication of PCBs or procurement of replacement components. Reproducing circuit boards is usually the faster resolution.

Surface‑finish related risks mostly manifest at the assembly phase. Compliance with IPC‑defined finish type and thickness specifications should be verified against shipping documentation. Overly thick surface finish creates processing difficulties for assembly operations. Lead‑free components require higher assembly temperatures than lead‑based components. Excessively thick finish causes assembly obstacles, product scrap and board rework. Insufficient finish thickness introduces separate risks. Surface finishes carry defined shelf‑life limits; too‑thin coating leads to poor solder wetting performance and significantly shortens the usable shelf life of PCBs.

There is no visual method to confirm compliance with IPC standards. Validation relies on manufacturers implementing proper process controls: applying correct finish types and target thickness values, performing ongoing process monitoring, completing thickness testing on finished products, and supplying factual supporting documentation. Specialized measurement equipment is required to accurately test surface‑finish thickness on received boards. If non‑conformance is suspected, independent third‑party laboratories can carry out verification testing.

Sizes

Build‑to‑print manufacturing means products are fabricated strictly per supplied fabrication drawings. All acceptance criteria for finished goods must be fully defined in supporting documentation. Specifications for overall PCB dimensions and hole sizes are frequently incomplete within provided drawing data. Board outline geometry may be provided, and industry‑standard fallback tolerances are widely adopted: ±0.005 for routed profiles and ±0.003 for plated hole sizes.

Incoming inspection processes must cross‑reference received hardware against source fabrication drawings for all physical dimensions. Inspect part number, revision marking, solder‑mask requirements, silkscreen requirements and surface‑finish requirements. PCB length, width, cutout features and overall board thickness must have defined tolerances, and finished units must satisfy those tolerance ranges. Calipers are recommended tools for verifying documented dimensional values.

Drill drawings need to specify all hole sizes, hole locations, plating status, corresponding tolerances and identification symbols for each hole dimension. Pin‑gauge sets are essential for incoming hole‑size inspection. Spot‑checking samples for each hole‑size category is standard practice. Holes manufactured either undersized or oversized will create major assembly‑related issues.

Summary

Preserve copies of online order receipts. Ensure project documentation clearly defines all expected product specifications, and use appropriate inspection tools to verify delivered PCB hardware.