Understanding the different inspection methods used in PCBA manufacturing helps you specify the right quality requirements for your project. Each method has different capabilities, limitations, and costs. This article explains what each method detects and when to require it.
SPI is performed immediately after solder paste printing, before component placement. It uses 3D optical measurement to verify that the correct amount of solder paste has been deposited on each pad — checking volume, area, height, and position.
SPI is the most effective preventive quality control step in SMT assembly. Catching solder paste defects before placement prevents the majority of reflow defects. At Kingdta, SPI is standard on all orders.
AOI is performed after reflow soldering. It uses high-resolution cameras and image processing to inspect every component on the board for: component presence and absence, component polarity and orientation, component value (for marked components), solder joint quality, and solder bridges.
AOI is fast and comprehensive for visible solder joints. Its limitation is that it cannot inspect hidden joints — BGA balls, QFN pads, and other bottom-terminated components are not visible to optical inspection. At Kingdta, 100% AOI is standard on all orders.
X-Ray inspection is required for components with hidden solder joints: BGAs, QFNs, LGAs, and other bottom-terminated packages. X-Ray can detect: BGA solder ball collapse, bridging between BGA balls, insufficient solder on QFN pads, and voids in solder joints.
X-Ray inspection is available at Kingdta for all orders. For BGA-containing designs, we recommend X-Ray as standard. For other designs, X-Ray can be specified as a sampling inspection or 100% inspection.
ICT uses a bed-of-nails fixture to make electrical contact with test points on the board and verify: component values (resistance, capacitance, inductance), component placement, shorts and opens, and basic functionality of individual circuits.
ICT requires a custom fixture for each board design, which has a one-time tooling cost. It's most cost-effective for medium to high volume production where the fixture cost is amortized across many boards.
Functional testing verifies that the assembled board performs its intended function. The test procedure and equipment are defined by the customer. Functional testing is the most comprehensive quality check but requires the most customer involvement to define and implement.
Design for Manufacturability (DFM) analysis is the single most effective way to reduce PCBA defect rates. This checklist covers the 12 most common DFM issues our engineering team identifies during pre-production review — and how to fix them before they reach the production floor.
Medical device PCBA has the most demanding quality and documentation requirements of any industry. This article explains the key requirements — IPC-A-610 Class 3, component traceability, process validation, and documentation — and how to evaluate whether a PCBA manufacturer can meet them.
Ordering small batch PCBA for the first time? This guide covers everything you need to know: what files to prepare, how to evaluate manufacturers, what questions to ask, and how to avoid the most common mistakes that delay projects and inflate costs.
