PCB Tech - PCB manufacturer, use penetrant dyeing test to view BGA solder

PCB manufacturer, use penetrant dyeing test to view BGA solder

The penetration dyeing test is a technique to check whether the surface mount technology (SMT) of electronic parts has soldering or cracking. This is a broken experiment, usually used in the surface mount technology (SMT) of electronic circuit board assembly (PCB Assembly), which can help engineers check whether the soldering of electronic parts is flawed. Because it is a destructive experiment, it is generally only used on circuit boards that cannot be detected by other non-destructive methods, and almost only used to analyze BGA (Ball Grid Array) packaged ICs, usually to better understand the product It can be used as a reference for quality improvement in subsequent production, or to clarify responsibilities.

The method is to inject the red potion (red ink) of appropriate viscosity into the BGA IC that is suspected of poor soldering habits. It is necessary to confirm that the red potion has completely entered under the BGA IC, and wait for a while or bake until the red potion is dry. Later, use a tool (usually a flat-head screwdriver) to pry directly from the circuit board (PCB), or use glue to stick the BGA IC and then use a pulling machine to hardly remove the IC. Note: The heating temperature cannot exceed the temperature at which the solder remelts.

In fact, I think this method is quite similar to the principle that ordinary plumbers or plumbing workers are catching leaks. First, pour a little solvent with a clear color, and then look at the leakage there.

The above is the method of self-made steel. The more professional method should cut off the suspected soldering problem on the circuit board, then soak the whole in the red potion, and then put it into the ultrasonic oscillator ( Ultrasonic cleaner) vibrate for a period of time so that the red potion can evenly penetrate into the depths of all the cracks, and then take it out for baking. The purpose of baking is to dry the red potion, so there is no need to use too high temperature, and then The sample to be tested is clamped into the jig, the BGA IC is pulled away from the circuit board, and then the staining phenomenon is observed with a high-power microscope.

Observe whether the circuit board pads (pads) and IC balls (balls) that have been pried up are stained red. If there is a poor soldering, such as cracks, empty soldering, etc., you can see that there is red potion. Mark of.

The principle is to make use of the penetration characteristics of liquid, which can penetrate into all gaps to determine whether the welding is intact. For general BGA ICs, both ends of the solder balls should be individually connected to the circuit board and the BGA IC body. If the red potion appears in the spherical place that should be soldered, it means that there is a gap in this place, that is, there is a solder break. From the rough surface of the welding fracture, it can be judged whether it is the original welding failure or the fracture caused by improper use.

Generally speaking, the surface of the solder with empty soldering and poor soldering is smooth, because the solder has strong cohesion, but there are exceptions, for example, oxidation or foreign matter contamination will also form a rough surface; as for the surface of acquired fracture, the surface is more irregular. The sharp bump surface.

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