In the production of LEDs, manufacturers had to face different problems. During their manufacturing process, LED bulbs are subjected to thermal and chemical stress, because the electronic components must be assembled.
During the welding, the peak temperature can be of even 260° C, which the LED will no longer reach during its lifetime. LEDs are also subjected to chemical stress due to the substances used during the welding, leading manufacturers to choose the most resistant material that can withstand these factors. For example, the plastic support of power LEDs has changed from a plastic material to a ceramic material because it is extremely resistant to heat and almost fully chemically inert.
To protect the phosphor that is fundamental for converting the blue LED into white light, the material that best reacts in terms of optical stability is silicone. Despite being extremely resistant to heat, chemical agents and oxidation, silicone is permeable to some chemical agents such as VOC (volatile organic compounds).
Some of these substances may already be present in the manufacturing process, while others may be found in the environment where the LED will be installed, such as for example in the varnishing paints of some manufacturing plants, in which – even if they are mostly eliminated by suction hoods – the vapours tend to accumulate upwards towards the ceiling where the lights are installed.