When I saw a WiFi camera for about $25, I wondered what was inside. I bought one to take apart and with the help of an X-ray machine at Tempo Automation I was able to not only look at the electronics but inside them. Here is what I found!
Like other cloud WiFi cameras, it works with a phone app. It connects to WiFi and sends video through the cloud and back to the app. It can also record locally on a flash memory card. There is little in the way of instructions, and it took some hunting on the manufacturer’s web site to figure out what it does.
The plastic case is made of injection-molded parts and comes with a magnetic base. A small module provides USB power. It is a bit of a puzzle box to get open. After removing the base, the back can be unsnapped.
There are three boards. The processor board has four layers, while the camera and microphone boards are two layers.
The Ingenic T20 processor can run Linux on its MIPS core using the GCC toolchain. It includes DDR2 RAM, video signal processing, video encoding, an ADC, and other peripherals. The serial flash memory IC provides storage. A WiFi module with a Realtek 8189 IC provides 2.4 GHz WiFi, with no 5 GHz option. This is a four layer board, with unfilled vias going all the way through the board. The connector latches to a flat ribbon cable which goes to the camera board.
The T20 processor X-ray reveals a thicket of bond wires connecting the processor chip to the BGA substrate. The round shapes are BGA solder balls, and the dark rectangles are the metal plates inside bypass capacitors. Resistors are faint because they have little metal, except on the solder terminations.
There are traces on the BGA substrate, also. Barely visible in this X-ray, these traces are smaller than the PCB traces.
The BGA substrate has two layers, with solder balls and fine traces on the bottom. Top and bottom connect through tiny vias. Side two has more traces and bond wires to the processor chip.
The back side of the processor board has an EA3036C 3-output DC to DC converter. It efficiently converts 5V from the USB power supply to 3.3V, 1.8V, and 1.1V.
The power supply inductors are large compared to the other components. These larger inductors handle more current than smaller inductors with the same value. Insufficient current handling in switching power supply inductors is a common source of failure in electronics.
There is extra solder flux in the lower right-hand corner of the microscope picture. This side of the board appears to be at least partially hand-loaded.
The optical picture shows excess flux around the USB connector. There is a puddle of shiny dried flux, flux powder, and solder balls. This flux can lead to corrosion. The solder balls can come loose and rattle around in the package, leading to short-circuits. One pin of the switcher IC has a blob of excess solder. This blob is visible in both the X-ray and optical images.
The X-ray image shows a lack of solder on one pin of the larger USB connector. One the four connections has solder only on the outer pad. The solder does not go through the board or create a fillet on the other side.
The smaller USB connector is used for power-only, and only the power pins are soldered. One of these power pins has no solder filling the hole. Through-hole connectors get extra strength from the solder connections. Leaving solder off of the unused pins misses an opportunity for strengthening the connector. Since this is a user-accessible connector, it needs all the strength it can get.
Two screws attach the lens assembly to the camera board. Removing it reveals the sensor and its rainbow of diffracted colors. A rubber gasket helps with the light seal. The vias are filled with black solder mask to help keep stray light out of the sensor.
A close-up X-ray of the camera sensor shows careful layout of every component, via, and trace. This camera sensor PC board has only two layers. The camera sensor BGA chip connects directly to its substrate. There are no bond wires from the sensor IC. The shape of the IC is visible in the X-ray as a faint but precise rectangle, visible just outside of the BGA ball array.
The third board provides infrared lighting for operation in the dark. It also has a microphone and a Micro SD card socket.
The challenge with soldering a microphone is to keep its internal solder joints from melting. The LEDs and microphone are hand-soldered with an overly generous amount of flux, similar to the USB connectors.
The X-ray shows an assortment of springs in the MicroSD connector.
The unloaded parts in the top left of the X-ray are for a light level sensor. Recent low-cost camera designs use the camera sensor instead of an external sensor for light level sensing.
The IC U13 on the right switches the infrared LEDs on and off. The power connector is on the left, and there is a big hole between the switch IC and the connector. The layout challenge is to make sure that the LED current does not flow in a loop around the hole, because this would be an unintended antenna to transmit EMI.
Tempo Automation’s quality greatly exceeds what is seen in these low-cost, high volume PCBs. The same X-ray machine used in these images inspects build quality at Tempo. X-ray and optical inspection data are available to customers to enable them to see the results of their builds.