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Inside Cell Phones
Inside Cell Phones
Abstract: Ever wonder what's inside your cellphone? We did, and so we cracked one open, took some pics and tried to explain a little bit of the mystery...

 Manufacturer  Category  Published  Author 
Qualcomm   Mobile Devices   May 29, 2000   Max Page  

Inside the Cell Phone

Cell phones are everywhere. Look to any corner of the street, office or home and chances are you will see at least one of them. While prices for cellphones have been dropping like a rock, new models are always more expensive than one's just a few months old and offer services like email, and internet access. But have you ever wondered what's inside these ever-shrinking devices?

Since we are fairly inquisitive around here, we cracked open a phone to see what was inside. Luckily there are even heatsinks in a cellphone, so there is at least one thing we can discuss. Antenna's were never my strong point :)

Let the dissection begin!

The Guinea pig for our little project is a Qualcomm 1960 digital phone. This phone and all its brethern were recently bought by Kryocera Wireless, though they are still marked Qualcomm. Using CDMA (Code Division Multiple Access) technology it operates on a output range from 0.2 - 0.006 watts.

Other bits if info I could dig up include the following. It operates within a frequency range of 1850-1910 for transmission, and 1930-1990 for receiving; the voice coders operate at 8 Kbps and 13 Kbps (PureVoiceT) and EVRC; it weighs about 120 grams.


 The first thing to come off of the phone was its battery. In most cases these are usually clip-on devices, this one was screwed into the back. Other then the fact that it is merle a collection of lithium Ion batteries in a heatshink wrapper, there really isn't much else to say.



With the back off of the phone, this is the first visible bit of electronics. The space where the black sticker sits is normally taken up by the battery.

Almost every group of components is hidden beneath the perforated metal shields. While their primary role is no doubt to protect against interference they can also serve another role. As they are soldered almost completely along the perimeter of the interface with the PCB they have the ability to pick up, an wick away, heat from the underlying components.

There is a really good article on Aavid's site, written by Christopher Chapman, entitled the "Basis of package/device Cooling" which address this type of cooling setup in good detail. Briefly though, it works on the principle that heat from the individual components is transferred into the PCB.

Now, assuming the substrate has a metal layer, it can then be used to aid in the cooling of the surface mounted components. In effect the copper layer that is used for the transmission of electrical signals can act like a thermal pathway. The tiny metal cages shown on the PCB may - and I stress may - be acting in this capacity, in addition to their shielding capabilities.

From normal use of a phone we all know they get warm if conversations last a while. In this case, the hottest spot seems to be on the lower right hand side. That particular enclosure is made from stainless steel and shows visible 'browning' just above an electrical component.

Other components that come to mind are the antenna, which extends up the left-hand side, and a curious solid-copper enclosure at the very bottom. From the side, this little rectangle of copper has cylindrical holes which extend part-ways into the block.


After removing the main PCB from the front of the phone, all that remains is the keypad, ear, and microphones. The keypad is a simple PCB with LED's attached sporatically - to light up the keypad when in use.

Why the inside of this portion of the plastic casing is coated in a fine metallic paint is something I can just guess at. I've seen the same kind of coating on some really cheap plastic computer cases. In those instances it was acting as a ground for the motherboard. In this instance, the PCB doesn't appear to have any visible means of using this to ground components.

The back portion of the phone is without this coating so... any ideas if this is supposed to cut down on signals radiating through ones' noggin?

Anyway time to move on to the computer that controlls the whole shin-dig... is it Intel or AMD !?!

° Next Page 

Table of Contents:

 1: — Inside Cell Phones
 2:  A cellphone's computer looks like....

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