Why Do Some Brand New CPUs Have Stains on the IHS?
If you’ve ever purchased a brand new processor (boxed or OEM/tray) and noticed faint stains or discoloration on the metal heat spreader (IHS), you might wonder why this happens and whether it affects performance. The good news is that it’s a completely normal occurrence and nothing to worry about.
During mass manufacturing and testing, thermal paste is applied to CPUs so they can undergo stress checks before shipping. After testing, the paste is removed, but in some cases, small traces may remain. This is where staining begins. It can appear as tiny spots, faint smudges, or light smear-like marks—what you’re really seeing are remnants of the factory thermal paste. Over time, the metal oxides within the paste can react with the nickel-plated copper surface of the IHS, leaving behind light discoloration or residue. Importantly, this occurs even though the processor has never been used by an end user.
While in an ideal world there would be no staining whatsoever, unfortunately this isn’t always the case. This effect is often more noticeable with OEM tray CPUs, which are supplied without retail boxes or sealed packaging. Because they are exposed to open air during storage and handling, trace amounts of oxygen and humidity can accelerate oxidation of any microscopic residue left behind after the paste is cleaned. In simple terms, the longer the CPU is exposed to air without being boxed, the more pronounced these cosmetic marks can appear.
These stains are common across many Ryzen processors, including sealed retail-boxed units—not just OEM tray CPUs—and are purely cosmetic. They do not affect performance, stability, or lifespan in any way.
At PC Tec UK, we supply OEM tray processors exactly as they leave the factory. From time to time, a CPU may arrive with light factory staining on the IHS. While they may not look flawless, we guarantee every processor is brand new and unused, and each one comes with our 30-day guarantee for peace of mind. Where you won’t see any irregularities, however, is the green substrate PCB beneath the IHS—this part always remains impeccable and unaffected.
If you happen to receive a CPU showing light stains or discoloration on the IHS, now you know that this is a normal result of factory testing and not a sign of prior use.