Win the game with soldered RAM
I come from a time when we used to have “LAN parties”. You would take your PC to a friend’s place and connect via token ring – and later ethernet – to play multiplayer together. Despite the fond memories, looking back, we did spend a lot of our time tinkering to get our ‘boxes’ running again after transporting them. A common cause of errors was the loosely connected processor and cooling unit, along with RAM sticks that had come loose.
The “ruggedization” of PC technology
A lot has happened since those glory days, and PC technology has massively evolved. Not only has computing performance increased, but the physical resilience of computers has significantly improved. Today, PC-like embedded technology is used even in the harshest environments. And I'm not talking about an untidy apartment filled with pizza boxes, soft drinks and teenagers, but rather shop floors, outdoor applications, vehicles, and trains, where embedded systems are exposed to everything from arctic cold and desert heat through to severe shock and vibration.
To run reliably in these environments, embedded computing technology must be hardened. To achieve this, high-performance Computer-on-Modules (COMs) based on x86 technology, like COM-HPC and COM Express, typically leverage soldered processors. However, memory modules are still often plugged in. Why is this the case?
Soldered CPU, plugged memory
Standard COMs following either the COM Express specification (in its compact and basic sizes) or the COM-HPC specification (client or server) usually utilize DIMM sockets to install the main memory. This allows customers to choose the DIMM vendor and capacity after purchasing the COM, and they can easily upgrade or change the memory later on if they want to. These are definitely advantages in terms of flexibility. However, these DIMM slots have limited resistance to shock and vibration. In extreme cases, heavy mechanical stress can cause standard memories to slip out of the socket while minor shocks and vibrations can compromise the functional reliability of RAM – pretty much the way transporting our boxes to LAN parties did back in the 90s.
If your design is intended to be exposed to potentially damaging shocks or vibrations, it is recommended to use a more reliable memory configuration. The optimal approach is to directly solder the memory onto the COM. This not only ensures ruggedness, but also reduces the bill of materials and enhances cost-effectiveness during production. Consequently, specific shock and vibration testing for system qualification becomes unnecessary.
When it comes to Small Form Factors (SFF) COMs like SMARC or COM-HPC Mini, using soldered-on memory is already common. And this is not only due to space constraints, but also to meet the demands of rugged use cases like transport applications, construction equipment, agricultural vehicles, self-driving robots, and many other applications in rough, mobile, and off-road applications.
With soldered memory and support for an industrial temperature range between -40 °C and +85 °C, even high-performance COM Express and COM-HPC modules can go into these applications. Here shock and vibration resistant stationary devices are another important application area for these kinds of modules, as digitization requires critical infrastructure protection (CIP) against earthquakes and other mission-critical events.
High-performance SFF COMs in the COM-HPC Mini or SMARC standard use soldered RAM by design due to size restrictions and intended use cases.
There is more to ultra-rugged designs than just soldered memory
But just taking ruggedization measures on the modules is not enough. Remember the LAN parties mentioned earlier? One very annoying source of failure was the cooling. It was quite bulky and heavy and therefore especially prone to mechanical stress. This makes the right cooling solution another decisive factor for truly reliable embedded designs. That is why you should take a close look at the cooling solutions offered by your module vendor. They not only have to be thermally efficient but must also be securely fastened to the module.
What else is important from a vendor? Well, an optional conformal coating – necessary for protection against corrosion from moisture, condensation, or sulfur – and a range of comprehensive service offerings should be available. These services should include shock and vibration testing for custom system designs, temperature screening, high-speed signal compliance testing, and design-in services to simplify the use of embedded computing technology.
In the LAN party days, soldered-on memory would definitely have made life easier for me. Instead of wasting time setting up my PC, I would have spent more time playing and “getting good”. Maybe THAT’S the reason why I lose when playing against my children these days…
