I have a new patient on the operating table. It is feeling very sorry for itself !
This particular patient is a decent brand of thermal camera that has a rubber boot around its case to protect it from bumps. Note I say "bumps" and not drops ! This cameras specs state that it can withstand a drop from 2m but I would not care to test that spec for accuracy !
The camera came to me as a victim of a "drop" that rendered it faulty. Today I opened her up for an inspection. All looked pretty much as it should at first glance but closer inspection provided the evidence I needed to determine what sort of drop deceleration forces were involved in the accident to assess what could have suffered damage in the process. Heavier components on PCB's can break free of the PCB or develop hairline cracks in them or their solder joints. No components fell out of the case when I opened it, which was both good and bad. Good in that a component escaping the PCB often means a very high energy deceleration event. Bad because a component coming off a PCB is easy to locate and repair. In some cases that may be the only fault.
So when assessing a dropped handheld equipment check the following:
1. Any obvious impact witness marks. Note where to establish impact point.
2. Are all screws present ?
3. Is the case still tight at its joints or burst ?
4. Once the case screws have been removed open the case and inspect the screw entry points and receptacles. Are they damaged ? If damaged, asses direction of failure and number of failed screw securing points.
5. Inspect the PCB's for obvious damage caused by flexing or chassis parts impacting components. In a deceleration event the longer PCB's can flex considerably and impact adjacent PCB's or case parts.
6. Inspect around all heavier components looking for cracked solder joints or cracks in the components case. Heavier components are typically larger capacitors such as MLC or large SMT electrolytic and Tantalum types, Inductors, components with heat sinks or really any component that looks large or dense enough to risk breaking its solder joints. SMT components can actually have very little solder holding them onto the PCB so are vulnerable to fracture in the joint.
7. Study the PCB's and identify the power supplies. In a thermal camera, there will be quite a few power supplies created using Boost and Buck converters. These are usually very easy to identify as they use physically large inductors, capacitors and a diode. The controller chips are normally a common Linear Technology part or similar so data sheets are available. Once all power supplies have been identified, a power on test may be carried out and all power supplies checked for reasonable voltages and ripple. A failed boost/buck inductor or capacitor would be evident by the voltage waveform produced at the output.
Beyond the above checks it becomes a normal fault diagnostic process as somewhere on the PCB's there will be a failed component and it is a case of zeroing in on it. Sadly BGA components do not make life easy if a solder ball joint has failed. Removal and reflowing is really the best solution if such is suspected. Some people just reflow without removal but this can provide variable results. Care is needed to not overheat the chip !
So what have I found on my current patient ?
1. The case showed no signs of impact damage but then it is rubber coated !
2. The case was burst slightly on one side
3. Once the case screws were removed and the case opened it was clear that of the 5 screw positions, 4 were sheared off ! Only one screw was actually achieving anything. The damage to the plastic screw mounting points was severe and shear rather than split. This camera contains a metal heatsink for the microbolometer that is secure in place by the case screws. The weight of that heatsink likely lead to some some serious energy entering the screw mounts. It is still unclear exactly which face of the camera impacted the ground first. The damage is serious enough to suggest a drop from a great height and not 'just' 2m.
4. There appears to have been enough energy involved in the drop event to damage components on the PCB's and potentially cause significant flexation in the main PCB due to its length and 'corner only' mounting fixing points. In such an event more than one component may be damaged. MLC's are particularly vulnerable to PCB flex induced damage.
5. This is a thermal camera with a fragile microbolometer and associated metalwork mounted on a PCB. The weight of the microbolometer module, which in this case is metal and around 1" x 1" x 1/4" in size, can mean that it suffers movement during the impact event. As the Microbolometer module leads are soldered directly to the surrounding PCB they can flex and exert destructive forces on the fragile glass vacuum seals. Failure of those seals causes loss of microbolometer vacuum. The microbolometer is then scrap
Time will tell how much damage has occurred within my patient. It could easily be a write-off due to microbolometer damage. On the other hand, it is a quality unit so the fault may lie on the PCB's due to flexation or solder joint failure.
I may provide more details of this repair but thought this brief commentary on this unfortunate camera might be of interest to others.
As I said in the title .... do not drop your thermal camera. Always use a safety lanyard or wrist strap. A rugged looking camera case covered in rubber can only do so much to protect the electronics within !
Fraser
Home
Help
Search
Login
Register
