PCB X-Ray
Inspection Services
X-ray inspection of BGA solder connections within PCB assembly.
FLJ examines selected hidden joints for solder-ball arrangement, bridging and voiding, and connects the findings with the relevant assembly and rework.
X-Ray Inspection for Hidden Solder Connections
FLJ provides X-ray inspection within PCBA manufacturing to examine solder connections concealed beneath components, including the ball array in a BGA assembly. We examine the selected joint arrangement and solder features, then connect relevant findings with the assembly work.
A BGA package blocks the surface camera’s view of its underside joints. X-rays passing through the assembly are attenuated differently by its materials and thicknesses, creating contrast that reveals internal structures such as solder connections. This gives the inspection a view of features beneath the package.
BGA Solder Joint Inspection
Ball Pattern and Joint Alignment
We compare the selected ball pattern with the expected connection sites, examining each joint’s projected outline and its position relative to neighboring joints. A shifted or apparently missing site directs attention to that connection for closer examination. The expected array provides the reference for interpreting an interruption in the pattern; the image also needs to distinguish the relevant joint from other features in its path.
Solder Bridges and Abnormal Joint Features
A solder bridge joins neighboring joint sites that should be separate. A connecting region between those sites directs the inspection to its position and shape relative to the expected separation. Other structures can project into the same area, so the review establishes which features form that image before relating it to the solder connection. This ties the finding to the affected joints and the relevant soldering work.
Solder Void Inspection and Measurement
Projected Void Area
When void area is measured, the percentage describes visible void regions relative to the selected solder-joint region in the X-ray projection. The numerator is the measured area identified as void; the denominator is the projected area of that joint. Define both boundaries, and count overlapping visible regions once. This is a two-dimensional area ratio: it does not show void depth or convert the projected shapes into three-dimensional volume.
Keep the selected joint boundary and the identified void region explicit when interpreting the percentage. Changing the joint boundary changes the denominator, even if the same visible void region is measured. The value is meaningful only with those image regions defined.
Void Location, Distribution and Acceptance
A cluster on one side of the projected joint and voids dispersed across it have different spatial distributions, even when their area ratios match. Distribution can matter when the connection also carries heat, as with a QFN central thermal pad. Depth or interface position is a separate question that calls for a view or method able to resolve that information.
The package, the joint’s role and the applicable product criteria determine acceptance. The projected area fraction supports that decision alongside the observed distribution; it alone is not a prediction of mechanical strength or thermal performance.
Image Interpretation and Inspection Coverage
A two-dimensional X-ray view combines structures along the beam path. Features at different heights may overlap, which can obscure the connection or interface being examined. The useful image must resolve that particular feature. Contrast also depends on material, thickness and capture conditions, so image brightness alone does not establish solder-joint quality.
X-Ray and AOI for Different Assembly Features
Scroll each table to compare methods.
| Merkmal | X-Ray inspection | AOI |
|---|---|---|
| Bridge between accessible leads | Connecting solder between adjacent joints, where the view separates their structures. | Can inspect exposed solder surfaces when lighting and optical access are clear. |
| Void within a solder joint | Projected void regions inside the selected solder joint. | An enclosed void is outside the camera’s direct surface view. |
| Solder distribution at exposed leads | Projected solder extent, subject to overlap from other structures. | Can assess visible surface shape where the lead and solder are unobstructed. |
| Merkmal | X-Ray inspection | AOI |
|---|---|---|
| Position and visible orientation | May show body placement when projected edges have enough contrast; it does not read printed marks. | Can check presence, position, and visible orientation markings with optical access. |
| Actual component value or electrical condition | Electrical measurement is needed to verify the actual value or behavior. | Optical appearance does not measure actual electrical value or behavior. |
| Merkmal | X-Ray inspection | AOI |
|---|---|---|
| Ball-array alignment | Can show the projected ball pattern when geometry and contrast distinguish the array. | Can inspect the package exterior, but not the covered ball array. |
| Bridge beneath the package | Can show a bridge when the projection distinguishes adjacent hidden joints. | Cannot view solder connections covered by the package body. |
| Subtle open interface or head-in-pillow | Visibility depends on view and geometry; a suitable angled view may reveal the interface. | Cannot directly view the hidden ball-to-solder interface beneath the package. |
Head-in-pillow involves incomplete wetting between a BGA ball and solder from the printed paste. A top-down projection can superimpose the two sides of the joint, masking their separation. A suitable view and imaging capability are needed to resolve that interface; an appropriate angled view may reveal it.
AOI-Inspektion evaluates visible assembly features. Electrical measurements and functional verification address circuit or product responses under their selected test conditions, including power, firmware and interfaces where required. These checks complement the physical information from an X-ray image.
X-Ray Inspection in PCB Assembly and BGA Rework
FLJ uses X-ray inspection after assembly to examine the specified hidden connections and locate solder features for follow-up. Where the finding confirms a soldering issue, the team carries out the relevant manufacturing correction and reinspects the affected feature. Inspection therefore remains connected to the actual joints and the work that produced them.
After Component Replacement
Für BGA component replacement, the work includes local removal, inspection and preparation of the exposed pads, and placement and soldering of the replacement device. Reinspection returns to the affected connections to examine their arrangement and relevant solder features after that work. The board condition and target component guide the local replacement process.
Inspection Images and Records
For orders that include documented results, FLJ supplies the specified images and inspection and test records. The record set follows the checks included in the order. Electrical or functional results are associated with their respective test scope, keeping the delivered information tied to the verification performed.
Discuss the assembly and inspection requirements for your PCBA project.