Silver is a precious metal that has been used for thousands of years. It has many unique properties that make it useful for various applications. One area where silver is used today is in cell phones and other mobile devices. In this article, we will explore the different ways silver is used in modern cell phones.
The Properties of Silver
Silver has specific properties that make it well-suited for use in electronics like cell phones:
– High electrical conductivity – Silver is the most electrically conductive metal, even more so than copper. This property allows silver to carry electrical signals very efficiently.
– High thermal conductivity – Silver conducts heat efficiently. This helps dissipate heat in electronics and keeps components cool.
– Durability – Silver is resistant to corrosion and oxidation. This helps it maintain connections over time.
– Antimicrobial – Silver ions inhibit the growth of microbes, which helps protect components.
– Solderability – Silver readily bonds with other metals, making it useful for soldering joints.
– Reflectivity – Silver efficiently reflects light. This allows it to be used for things like mirrors.
These unique properties make silver applicable for various roles in modern electronics like cell phones.
Silver in Cell Phone Circuits and Wiring
One of the main uses of silver in cell phones is in the circuits and wiring. Silver has the highest electrical conductivity of any metal. Because of this property, silver is an ideal material for carrying electrical signals in the tiny, intricate circuitry inside a cell phone.
Silver wire and traces are embedded into the printed circuit boards (PCBs) that contain the chips and components making up the phone’s processor, radio, camera, and other sub-systems. This allows signals to travel quickly through the PCB pathways to execute the phone’s functions.
Compared to another highly conductive metal like copper, using silver in PCB traces gives a higher conductivity while taking up less space. With cell phones constantly shrinking in size, silver allows conductive paths to be made smaller and thinner.
Silver’s durability also makes it maintain a stable connection over time, unlike other metals that degrade. Overall, silver’s superior conductivity and durability make it an essential metal used in the critical phone circuitry carrying out the electrical signals powering the phone.
| Metal | Electrical Conductivity |
|---|---|
| Silver | Highest |
| Copper | 2nd highest |
Silver in Solder
Another place silver is found inside cell phones is in solder. Solder is a metal alloy that is melted and used to join electronic components together.
The commonly used solder for electronics is called SAC solder. It consists of tin combined with silver and copper (SAC standing for silver, copper, and tin).
The silver comprises 3-4% of the solder alloy. It is added to the solder for two main reasons:
1. Silver lowers the melting point – Adding silver to solder reduces its melting temperature, which makes it easier to work with. The solder needs to melt at reasonably low temps to safely join phone components.
2. Silver improves joint strength – The addition of silver creates stronger joints between components mounted to the PCB. The solder bonds tightly, providing a durable connection.
So while only making up a few percent of solder, the presence of silver allows phone solder to create the many robust joints within the device. These solder joints are found throughout a phone, attaching things like the processor, resistors, capacitors, and connectors to the PCB substrate.
Silver in Batteries
Modern cell phones use lithium-ion batteries to provide power. One place silver is found in phones is in the chemistry of these batteries.
The lithium-ion batteries contain two electrodes – a cathode and anode. The cathode is where the lithium ions move to and from during charging/discharging.
In many lithium-ion batteries, the cathode contains a silver vanadium phosphate chemical compound. For example, LVP batteries (lithium vanadium pentoxide) use a silver vanadium cathode material.
The silver improves some performance factors of the cathode:
– Increases electrical conductivity
– Enhances thermal stability
– Improves structural stability
This improves the battery’s overall power output, lifetime, and safety. So while the percentage of silver in an LVP battery cathode is small, its presence enhances the battery performance.
Other lithium-ion batteries may use different cathode chemistries, but silver is commonly included in small amounts to enhance electrical characteristics.
Silver in Phone Contact Points
Silver plating is often used on contact points inside cell phones. For example, the SIM card slot has connectors that have silver plating on their surface. The headset jack, charging port, volume/power buttons, and more also use silver plated contacts.
The silver plating provides a few benefits:
– High conductivity – Silver optimizes electrical flow from plugs and cords into the phone’s internal components.
– Corrosion resistance – The silver inhibits moisture damage and oxidation, improving durability.
– Hardness – Silver plating deposits a thin layer of hardened silver on top of base metals, providing abrasion resistance.
– Antimicrobial – Silver ions prevent buildup of microbes on frequently touched surfaces.
While the silver plating on contacts is only microns thick, it enhances transfer of power and signals into the device while reducing corrosion over the lifetime of the phone.
Silver in Solders and Alloys
In addition to solder, silver is sometimes mixed into alloys used in cell phones:
– Silver-cadmium oxide (AgCdO)
– Silver-zinc (AgZn)
– Silver-tin oxide (AgSnO2)
These compositions containing trace amounts of silver are chosen for things like RF shielding or electrical contacts in phones.
The silver improves solderability, conductivity, and corrosion resistance. It also makes the alloys more heat and UV radiation resistant. So silver as an alloy additive provides enhanced performance in niche applications.
Silver in Conductive Adhesives
Conductive adhesives are used in cell phones as an alternative to solder for attaching components. Traditional solder requires heating up the parts being joined, which can damage temperature-sensitive phone parts.
Instead, conductive adhesives can stick components together without heat. Many adhesives used for phones contain micron-sized silver particles to make them electrically conductive.
The silver particles join together, forming many tiny electrical pathways through the adhesive. This allows electrical currents to travel through the adhesive, providing conductivity from one part to the other.
These silver-filled electrically conductive adhesives are useful for adhering battery tabs, chips, capacitors, and other parts that can’t tolerate high heat. The silver enables conductivity while the adhesive provides bonding.
Silver in Capacitors
A capacitor is a small electrical component used to store electric charge temporarily. Cell phones contain many capacitors of varying sizes.
Some capacitors contain silver in their design. For example, certain types use silver palladium electrodes. The silver improves conductivity and allows the capacitor to function properly.
Silver is also sometimes used in ceramic capacitors. These contain silver electrodes and layers that are beneficial for providing high capacitance and low loss.
Using silver instead of other metals in these capacitors enhances their electrical performance. This is critical in cell phone circuits where capacitors need to rapidly charge and discharge.
Downsides of Using Silver
While silver clearly provides benefits in cell phones, there are also some downsides that limit its use:
– Expense – Silver costs substantially more than metals like copper or tin. This restricts the amount of silver used. Only trace amounts or coatings are cost-effective.
– Weight – Silver has a density nearly 10x that of plastics used in phones. So silver or its alloys add weight compared to other materials. Keeping phones light limits silver quantities.
– Supply limitations – There is less silver available in the Earth’s crust compared to more abundant metals. Global silver supply is constrained, making it more expensive.
– Thermal processing – Certain assembly steps for phones require heating to high temperatures. Silver tends to leach or migrate out of alloys when processed at high temperatures, limiting its use.
– Solderability challenges – While silver improves solderability, it can sometimes create tin whiskers on solder joints. This can harm conductivity, so optimal silver content must be balanced.
Conclusion
In conclusion, silver is used in small but important amounts in many areas of modern cell phones:
– Circuits and wiring
– Solder
– Batteries
– Contact points and connectors
– Specialized alloys and adhesives
– Capacitors
The inherent properties of silver including high conductivity, thermal properties, reflectance, and antimicrobial ability provide unique benefits for phone function and reliability.
However, cost, availability, weight, and processing challenges limit its use to mainly trace amounts for coatings, compounds, and performance-enhancing additives. Going forward, advances in technology will likely expand silver’s role in maximizing performance in the incredibly complex electronics of mobile devices.
