Quote:
Originally Posted by stumped
I very much doubt that some devices have a coloured led where a white should be, as surely the LEDs are auto inserted by some mass production machine, not some individual with 2 boxes full soldering them in one at a time?.
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Indeed this was the reason PCBs were invented in the 1950s. Initially some parts had to be hand inserted. Soldering was by wave.
By the mid 1980s mixed surface mount and through hole with 100% machine placement or insertion was possible.
In the 1960s the surface mount used alumina substrates and a mix of oven soldered paste (screen printed) and hand soldering as it was low volume aerospace. By the mid 1980s companies were switching to all surface mount if possible for higher speed fully automated assembly. There were problems for a while with relays, switches, sockets and electrolytic capacitors.
I would suspect from my experience designing stuff that there are problems with the light pipes (plastic sheets) and also sometimes software. I've seen any number of cheaper LCD monitors, laptop screens and LCD TVs since 2005 with bad LED lighting. The CCFL tubes were expensive, took more space, needed a high voltage and can be fragile. However they are more even and often a better white. Cheap LCD products use a few LEDs along the edges. Expensive ones use arrays behind the panel. The eink uses the cheap LCD edge LEDs method, as obviously a rear lighting array can't work, but with the light pipe panel on top of the display. Mechanical alignment is critical as anyone trying to reassemble an original H2O bezel for IR touch. Hence the light pipe layer is bonded to the screen with the capacitive sense layers and overlaps the LEDs on the main PCB.