BGA solder joint inspection and a sound repair decision are among the most delicate parts of working with industrial electronics. Not every failure of a BGA-packaged chip requires full reballing. Sometimes restoring power rails and adjacent circuits is enough; in other cases the device will fail again within a week without ball replacement. Below we explain how we diagnose BGA joints, what data we gather, and the criteria we use to choose between local repair and reballing.
Why BGA is a distinct challenge
In a BGA (Ball Grid Array) package, the pins are an array of solder balls under the belly of the chip. They are invisible to the eye and out of reach for a probe, which means classic inspection methods only work in part here. And yet the solder joints under a BGA are a frequent point of failure: thermal cycling, vibration and solder ageing cause cracks that show up as floating faults.
A BGA failure almost always looks the same from the outside: the device runs unstably, freezes on warm-up, or stops responding after mechanical load. The cause, however, can vary from a single cracked joint to degradation of the die itself. The task of diagnostics is to tell one from the other, without spending effort on unnecessary reballing and without releasing a board with an unfinished repair.
X-ray inspection of solder balls
The main tool for assessing BGA joints is X-ray inspection. It lets us see what is hidden under the body: the shape and uniformity of the balls, voids inside the solder, bridges between adjacent balls, and signs of cold joints.
We carry out the assessment to the IPC-7095 standard, which covers the design and inspection of BGA assemblies, including the allowable percentage of voids in a ball and the acceptance criteria for a joint. Some typical X-ray findings:
- Voids above the limit. Small voids are acceptable, but a large void in the center of a ball reduces mechanical and electrical reliability and often causes an intermittent fault.
- Bridges between balls. A solder short between adjacent pins that is completely invisible from the outside.
- Uneven or collapsed balls. A sign of a disturbed thermal profile during previous assembly or of a degraded joint.
- Component shift. Displacement relative to the pads, affecting part of the pins.
Thermal profile and failure history
X-ray shows a static picture, but a repair decision also needs the dynamics. So we capture the thermal profile of the failure: through the thermal camera we watch how the chip behaves as it reaches operating conditions and under load. Local overheating of the BGA area, or conversely a loss of signal on warm-up, points directly to a joint problem rather than a power one.
The board’s service history matters too. A failure after long operation under vibration, after thermal shocks, or after a previous poor repair speaks to a different nature of the defect. Equipment from ships and metro systems arrives with characteristic vibration loads, and this changes the likely cause and the repair strategy.
Decision criteria: local repair or reballing
Once the data is gathered, we make the decision with clear logic.
Local repair is enough when the X-ray shows healthy balls under the BGA itself and the cause of failure is in adjacent circuits: power, support components, connectors or traces. In that case there is no need to touch the chip, and we restore the surroundings, confirming the diagnosis on BoardMaster using known-good comparison.
Reballing is required when the defect is in the joints themselves: cracks, critical voids, bridges or solder degradation under the body. Then the chip is carefully removed, the pads are cleaned, fresh balls are applied with the correct thermal profile, and the component is reinstalled.
Replacing the chip itself is needed if the X-ray and thermal profile point to die degradation rather than a joint. Reballing would achieve nothing here, and the honest answer to the customer is to replace the component, not the balls.
This analysis saves both money and the board’s remaining life: we do not reball where a local repair suffices, and we do not release a board with a cosmetic repair where the balls need replacing. It is part of our approach described in the article on component repair versus module swap.
Standards and quality of work
We perform all BGA operations to IPC standards. IPC-7095 sets the inspection criteria for BGA assemblies, while IPC-7711 and IPC-7721 describe the accepted methods for removal, soldering and board repair. Work follows ESD requirements, with a controlled thermal profile and a mandatory repeat X-ray inspection after reballing to confirm the quality of the new joints.
After repair the board goes through load testing, because the real reliability of a BGA joint shows up in operation, not in a static image.
What the customer gets
For the customer, precise BGA inspection means a decision based on data, not guesswork. We do not push expensive reballing where a local repair suffices, and we do not risk a repeat failure where the balls need replacing. As the outcome of diagnostics, you receive a clear report with X-ray images and a justification for the chosen strategy.
If you have a board with a BGA component that behaves unstably or failed after load, bring it in. We will run the X-ray inspection, capture the thermal profile and tell you honestly what exactly needs to be done. You can discuss the task through our contact page.