The Chemistry of a Graphics Processing Unit (GPU)

Introduction

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A Graphics Processing Unit, or GPU, is used primarily in rendering 3D graphics.  I chose this topic because I have a very high interest in Computer hardware,software, and how both work.  I am an avid gamer and play video games daily.  My personal GPU helps my computer to render the graphics of the games I play quickly and smoothly.

Composition of ...

  • The Graphics Processor

    • Transistors

    • Trade Secrets

  • PCI Express (peripheral component interconnect)

    • Circuit board

    • Gold

  • PCB (Printed Circuit Board)

    • Fiberglass

    • Epoxy resin

    • Copper foil


Main Chemicals, Compounds, Components

  • The Graphics Processor

    • The graphics processor utilizes transistors, semiconductor devices used to amplify or switch electronic signals and electrical power.  They’re used to execute calculations related to 3D graphics.  Transistors are generally made from silicon (Si).  The graphics processor is used in order to display graphics in a game or in a graphical developing program.  It can either be a stand alone graphics card inserted in the motherboard through a peripheral component interconnect (PCI) slot or integrated in the CPU.

  • PCB (Printed Circuit Board)

    • The PCB allows the electrical signals to move to the correct components on the board.  It’s made of fiberglass, copper foil, tin lead antimony (SnPb₂), and epoxy resin.  It’s in action whenever the GPU is in use.  The PCB is used so that all of the components can be organized together and can communicate correctly.  It’s located inside a computer hooked into a PCI slot.


Chemistry's Role

The Graphics processor is made from transistors.  Transistors are made from group VI elements, generally Silicon and Germanium.  Silicon is the more commonly used of the two.  The transistors are made extremely small and are packed as closely together as possible.   Everything else regarding how they are made is a closely guarded trade secret.

Chemistry shows its role through the use of silicon.  Silicon is classified as a semiconductor.  The use of a semiconductor in a graphics processor allows the electric signals to move to where they need to go faster in one direction than the other.  Their electrical properties can also be easily altered by applying electrical fields or light, thus making their applications more flexible.  Semiconductors also do not hold heat as easily, which is essential in the manufacturing of computers.  As the semiconductors get hotter, their resistance decreases and their resistance is a main reason why they are used. So their ability to not get as hot is detrimental.

The PCB (Printed Circuit Board) is made many elaborate steps.  First, the panels are stacked in layers, alternating with layers of adhesive-backed copper foil.  The stacks are placed in a press where they are subjected to extreme temperatures and pressures for an hour or more.   This fully cures the resin and tightly bonds the copper foil to the surface of the substrate material.   Holes are drilled according to the pattern determined when the boards were laid out.  The panels pass through a vacuum chamber where a layer of positive photoresist material is pressed firmly onto the entire surface of the foil (A positive photoresist material is a polymer that has the property of becoming more soluble when exposed to ultraviolet light).

Next, the printed circuit pattern mask is laid on top of the photoresist and the panels are exposed to an intense ultraviolet light.  Because the mask is clear in the areas of the printed circuit pattern, the photoresist in those areas is irradiated and becomes very soluble.  The mask is removed, and the surface of the panels is sprayed with an alkaline developer that dissolves the irradiated photoresist in the areas of the printed circuit pattern, leaving the copper foil exposed on the surface of the substrate.  The panels are then electroplated with copper.  The foil on the surface of the substrate acts as the cathode in this process, and the copper is plated in the exposed foil areas to a thickness of about 0.001-0.002 inches (0.025-0.050 mm).  The areas still covered with photoresist cannot act as a cathode and are not plated.  Tin-lead or another protective coating is plated on top of the copper plating to prevent the copper from oxidizing and as a resist for the next manufacturing step.  

Finally, the photoresist is stripped from the boards with a solvent to expose the substrate’s copper foil between the plated printed circuit pattern.  The boards are sprayed with an acid solution which eats away the copper foil.  The copper plating on the printed circuit pattern is protected by the tin-lead coating and is unaffected by the acid.

The role of chemistry in the pcb is simple.  Copper is a very good conductor of electricity.  The copper paths in the pcb allow for an electrical current to flow through the board and to the correct components that will be placed on the board.  Thus allowing the components on the board to communicate and carry out their tasks.



Background Research

A Graphics Processing Unit (GPU) is a specialized electronic circuit designed to rapidly manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display.  GPU’s are generally made of aluminum, silicon, gold, copper, and other closely guarded trade secrets.  In order for the GPU to work correctly, electricity needs to flow in a certain way through the board and its various components.  These different components are a graphics processor, peripheral component interconnect (PCI), heat sinks, heat pipes, video memory, and a circuit board.  Two main Companies, Nvidia and AMD dominate the GPU market with the graphics cards that they manufacture.

Resources


About the Author
Noah Schmall is a junior at Billings Senior High School. He enjoys learning about computers, their different components, and how they work. Noah hopes to attend Montana State University to explore his interests in computers in-depth. He is currently enrolled in many honors classes and plays soccer for his high school and the city traveling league.







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