Introduction

A few weeks ago, I took an LG G3 smartphone apart to repair the screen. I hadn’t disassembled a recent smartphone for a while, so there were some interesting finds which I’ll document here. My apologies for the crappy photos.

Force-resistant headphone jack & Bottom sensing MEMS Microphone

Most noticeable was the headphone port, which is a discrete part with springy connectors on the side. These mate to an edge-connector on the PCB. The part was mounted only to the enclosure (with adhesive), not to the board. Since the headphone port gets to endure considerable stress from the forces of the earphones, this makes for an interesting solution to headphone ports fatigue-cracking from the PCB. This should make the phone more durable (on that part; it has other issues like easy moisture ingress). It’s also easier to replace.

Another interesting solution visible in these photos is the MEMS-microphone, which has its sound-cavity-opening on the bottom in stead of the top. On the bottom of the board is a small piece of filter or membrane which keeps out dust (and maybe moisture as well?). The phone features three of these, with the other two used for noise-cancellation.

Distance sensor mounted on a small piece of circuit board

This is an interesting hack solution which I’d never seen: mount a part on a small piece of circuit board of a certain thickness, to use as a spacer. This way, you can have the sensor as close as possible to the front glass. The green PCB has tiny vias (visible through the epoxy!) and presumably some pads on the bottom to SMT-mount it to the blue mainboard. I wonder if these were populated on a big panel with loads of these sensors and then cut and repackaged on reels to feed into the main assembly-process?

PCB-mounted shielded high-frequency cable

You’ve got your high-frequency signals on one side of the board and your antennas on the other. What’s a guy (or gal) to do? The cable is about 5cm long and runs on a thin strip of PCB which is besides the battery (which would be in the bottom left in this photo).

Laser-etched-then-metalized plastic parts with vias

Using a laser to roughen the surface of a plastic part and then using the surface roughness to selectively metalize the part has first been demonstrated by Fraunhofer (AFAIK) quite some years ago. It’s been used extensively to make high-performance antennas from the parts that also function as the speaker body or phone enclosure. I’d never seen this process done with functional vias (electrical connection from one side to the other) before. Hybridica FTW!

Thanks for your attention! See anything else interesting? Questions?

Like this? You might be interested in my latest project. It's a desk light made completely from a single sheet of printed circuit board. Check it out: