Teardown Of A Philips Dimmable Led Bulb
Posted by Waston Chen on
Here is from the part from the Video of bulb lover:
One of the first things you will notice about this light bulb is that the compact construction. Most noticeably the lack of the telltale heatsink fins. As a result however, the heat dissipation capability is greatly sacrificed.
During normal operation when mounted pointing downwards without any airflow obstruction, the case temperature raised to above 60°C within a few minutes. I could only imagine what the temperature would be like when the light bulb is mounted facing upwards in a semi-enclosed light fixture.
So I decided to take it apart to see the what the construction looks like inside.
Thank you for the very instructive video from youtube.com, for me, had no idea how they worked until your demonstration.
From a mechanical engineering perspective the bulk of the heat generated by the circuit board and LEDs would best be removed to the environment through conduction to the metallic base that screws into the lamp holder. I suspect that there should be a heat conduction path from the metallic plate that the LEDs are mounted on and then to a flexible heat conductor inside the white insulating material that separates the LED mounting plate from the metallic base that screws into the lamp holder. Heat removal by radiation and convection through air currents around the light emitting portion of the bulb would be less effective than heat conduction through metallic components. Thus it would make much difference whether the bulb was pointed up or down. Whether or not my thoughts above are correct, it’s obvious that the circuitry required to make the LEDs functional are much more susceptible to heat damage than other types of bulbes.
You may gave them too much credit to this bulb. They are just spreading the heat around with the aluminum heat sink, I suspect they think it’s acceptable for a 7W design. To be sure, they aren’t going to maximize longevity for our sake.( Elevated temps is a design decision. Rather disappointed with Philips, they aren’t cheaply priced (but it seems they are cheaply made, ha ha.) But dying after two months and the rest over one year is indicative of a defective design. Or an evil OEM. Bad, bad Philips, it just kills my trust in them, but then most others can’t be trusted as well. Maybe Philips has been taken over by marketing types and bean counters, like Intel.
I think you are too optimistic about E27 screw holders. I don’t think metals are touching in a lot of places, otherwise how would you unscrew it? Conducting area is actually not big, and the E27 holder is just thin metal, enclosed in plastic and thus is not really a good heat sink. There is only two not-so-thick wires to the E27 screw base. The main heat spreader is the aluminum cylinder, that’s all, ugly. Poor electrolytics and LED dies, must have been hellish in there.