PCB X-ray inspection for solder joints, BGA voids and hidden defects

Most electronics X-ray jobs fall into one of three service levels, and the level drives both what you learn and what you pay.

For a lot of 20 boards with one BGA each, 2D with a few oblique views is usually enough. For a field return that failed intermittently, most labs start with 2D, then move the suspect joint to CT before they cut it. Our industrial CT scanning page explains how voxel size limits what a CT scan can see.

Electronics X-ray results mean little without a stated criterion, so say which one applies in the request.

• IPC-A-610, the acceptability standard for assemblies, by product class 1, 2 or 3. For collapsing BGA balls it sets a void limit as a percentage of the ball's X-ray image area, and labs commonly quote 30 percent per ball. Confirm the figure against the revision your contract names.
• IPC J-STD-001, the process requirements standard that many defense and aerospace contracts cite alongside IPC-A-610.
• IPC-7095, the BGA design and assembly guidance that separates process control voids from voids that need corrective action.
• IPC-7093, the guidance for bottom terminated components such as QFNs, where large thermal pad voids are normal and limits are agreed with the customer.
• Your own drawing notes or customer specification, which override the general standard. Automotive and medical customers often set a tighter limit on thermal pad voiding.

A good lab report states the criterion, the class, the void number for every joint inspected and which joints failed. If the report only says "acceptable", ask for the numbers.

Contract manufacturers send first article boards and rework samples when a customer asks for proof of BGA quality. OEM quality teams order X-ray on incoming lots from a new supplier, or when a field failure points at one package. Small hardware companies without their own X-ray system use a lab for every new board revision, because buying an inline or benchtop machine rarely pays off below steady weekly volume. Defense and aerospace suppliers need documented X-ray for Class 3 builds, and battery and power electronics teams use it on die attach and busbar joints. For battery cells and full modules, see battery CT scanning and electronics inspection.

1. You send the board count, board size, which packages to inspect, the criterion and class, and whether the boards are double sided.
2. The lab confirms the imaging level, 2D, oblique or CT, and quotes per board, per hour or per package.
3. Boards ship in ESD packaging. Many labs also accept hand delivery for urgent lots.
4. The technician images each package, measures voids and takes oblique views of anything suspect.
5. You receive a report with images, a void table per joint and the pass or fail call, plus raw images or CT data if you asked for them.

Standard turnaround is commonly one to five business days. Same day and next day service exists at many electronics labs for a rush fee.

Price follows the imaging level, the number of packages per board and the report detail. These are typical US ranges for planning, not quotes.

Most labs charge a minimum, often one hour. Grouping boards into one order, inspecting only the packages at risk and agreeing on a sampling plan cuts the bill more than haggling on the hourly rate. Our guide to NDT inspection cost covers how inspection labs build a quote in general.

Ask four things before you send boards. First, what resolution the system reaches on your ball pitch, since a 0.4 mm pitch package needs far finer focus than a 1.27 mm one. Second, whether the lab has oblique and CT capability in house, so a suspect joint does not have to go to a second lab. Third, whether the report gives a number per joint and names the standard revision. Fourth, whether the lab holds ISO/IEC 17025 accreditation or an IPC certified operator for the work, which matters for audit trails. Our list of NDT companies explains how to compare labs on scope rather than on price alone. If you are not sure X-ray is the right method at all, for example on a casting or a sealed housing, the guide CT vs X-ray inspection for castings walks through the same trade off on metal parts.