Colour of integrated circuit packages

Hi,
Can anyone please tell me why are all chips colored black? Is it something to do with power consumption or something like that?

Semiconductors are affected when exposed to light. For instance a photo-transistor is nothing more than a regular transistor with an exposed 'window' to the PN-Junction in place of an electrical base input. The black plastic blocks light from exposing the material.

Back in the late 1990s I was debugging a microcontroller circuit that was acting strangely. This was before flash devices were common, so debugging was done with UV-erasable parts.

The circuit wasn't working, but as I went to put a scope probe on one of the pins it started to work. The really strange part was that I hadn't touched the pin yet. After some experimenting, I found that just moving my hand near caused it to work. I suspected a floating input, so double checked that MCLR and such were tied high or low or had pullups/pulldowns. I tried touching ground and Vdd with the other hand and leaving my body floating, but nothing seemed to matter.

After much head scratching I eventually realized that the hand was blocking light from a nearby window. I was just trying a quick and dirty test and hadn't bothered with the sticker over the UV window identifying the firmware version number like I usually did. After all, room light or even outdoor light thru the window was nowhere near enough to erase the chip. It wasn't, but what I forgot to consider was light effecting the normal operation of other parts of the chip.

I never left off the sticker over the window after that. Fortunately things transitioned to flash instead of UV erasable a few years later.

I have scene a few optocouplers that have a white plastic body. I always assumed that they had some special material to help further insult light, but that the white plastic was good for transmitting the light within the chip.

One of my projects back in the day involved using a cypress usb microcontroller. The device was a OTP (one-time programmable) part and I had about 5 on hand.

We didn't have a good way to debug our code (that was written in assembly language) and I started to burn through this lot of parts in a hurry. This was a very early USB device and so debug was a crapshoot at times.

Luckily one of the guys had a suggestion that I take the part down to the processing lab and have them etch down the part to expose the die.

I took down about 5 already programmed parts and the technicians managed to open up 2 without damaging the bonding wires.

Then, I grabbed a UV erase light and had myself a set of re-programmable parts!

Yes this was one of the question in my mind from so many years but never googled.Thanks vinit for putting it here.

@kevin sir: Yes Semiconductors are greatly affected when exposed to light so there is a need to block light.
In the mean while heat also greatly affects semiconductors, if the Integrated circuit package is made of Black then it absorbs more heat from light and also atmospheric temperature and rises up the temperature of the IC package and affects its working.

so why not they color it white instead of Black which perfectly reflects both light and heat?