If you are trying to source a replacement for an obsolete memory module and running out of options, this article explains how specialist replacement engineering works, what qualification looks like in practice, and what to do if you have a part number and no supplier. It draws on a recent Force Tech Talk episode featuring Karen Salmon FIIOM, Ben Savage MIIOM, and Charlotte Hughes AIIOM.
Why Obsolete Memory Modules Are Becoming Harder to Source
Obsolete memory modules are harder to source because the manufacturers who produced them no longer exist or have stopped making them, while modern manufacturers have shifted capacity to DDR and flash production for consumer electronics, data centres, and AI workloads. That leaves a growing gap for the older SRAM, EPROM, EEPROM, and hybrid module types that long-life programmes still depend on.
Memory module manufacturers have consolidated significantly over the past two decades. White Technology, once an important supplier to the aerospace, defence, medical, and industrial sectors, was acquired and its new owner discontinued module production entirely. Engineers running legacy systems built around White Technology parts, identifiable by WM, WF, or WS prefix part numbers, now have no conventional route to supply.
The problem is compounded by the fact that newer memory devices are not simple drop-in replacements. Switching to a modern device typically requires a board redesign and full requalification, which is not viable for most long-life programmes.
What Makes Memory Module Replacement Difficult
The core constraint on any memory module replacement is that the pin-out, footprint, and function must all stay the same. Changing any one of these requires redesigning and requalifying the board, which is not a practical option on a long-life programme such as Eurofighter Typhoon, where the original memory module designs may date back to the early development phase.
This is exactly what makes form, fit, and function replacement engineering valuable. Rather than redesigning around a new device, a specialist supplier reconstructs the original module using currently available components, preserving the interface the system was designed for.
The memory types most commonly affected include SRAM modules, E²PROM modules, EPROM modules with UV-transparent LCC lids, and hybrid modules combining two or three memory technologies on a single substrate.
How Replacement Memory Modules Are Built
Replacement memory modules are built using one of two approaches: stacking or multi-die packaging. Both allow higher memory density to be achieved within the same physical footprint as the original device.
Stacking places individual die vertically within a single package, connected through the stack using fine wire bonds or through-silicon connections. Multi-die packaging places multiple devices side by side within a single carrier, using decoder logic to manage addressing. Early examples of this approach date to the late 1980s, when manufacturers combined four 1-megabit E²PROMs on a substrate to replicate a 4-megabit E²PROM in the same 32-pin DIP package. The principle has not changed; the components have.
Substrate choice depends on the application. Ceramic substrates are standard for European aerospace and defence programmes, offering hermetic sealing and the thermal stability those environments require. US programmes are generally more open to plastic substrates, particularly where the system-level enclosure provides environmental protection.
There is also growing demand for system-on-substrate solutions, modules that combine memory with logic or interface devices in a single package, preserving footprints that the original design team created to solve density problems that commercial single-chip devices could not solve at the time.
What Qualification Looks Like in Practice
Qualification of a replacement memory module follows one of two paths. The first qualifies individual components to MIL-STD-883 before assembly, then performs continuity testing on the completed module. The second qualifies the completed module as a whole, which is more common when stacking introduces mechanical risk that component-level qualification does not fully address.
Vibration and shock testing is a consistent requirement across aerospace and defence programmes. Engineers specifying replacements will almost always ask for evidence that the module survives the mechanical stress of its operating environment. This is not optional; it is captured in the qualification plan from the outset.
Access to original design data makes the whole process considerably more reliable. For White Technology parts and several other discontinued module ranges, that data has been retained by suppliers with a long history in the sector. Starting from original design data is far preferable to reverse-engineering from a physical component alone.
White Technology Memory Modules: What to Do If You Have a WM, WF, or WS Part Number
If you have a White Technology part number with a WM, WF, or WS prefix and no route to supply, the first step is to establish whether original design data still exists. That data has been retained by suppliers with a long history working alongside White Technology during its active years, and it significantly reduces the time and cost of reconstructing a replacement module.
Bringing the part number to a specialist is more productive than attempting to reverse-engineer from the component alone. The original design intent, substrate specification, and interface requirements are all captured in the design data, and working from that baseline produces a more reliable replacement.
How Force Technologies Approaches Obsolete Memory Module Requirements
Force Technologies has been working in obsolete and end-of-life semiconductor solutions for close to four decades. Memory modules have been part of that work from the beginning, covering SRAM, E²PROM, EPROM, hybrid, and system-on-substrate types across aerospace, defence, medical, rail, and industrial programmes.
The team, including Ben Savage (Applications Manager) and Charlotte Hughes (Commercial Director, AIIOM member), assesses each requirement individually. The starting point is always the part number and the application context. From there, the team can advise on what replacement options are feasible, what qualification path applies, and what timescales are realistic.
If you have a legacy memory module requirement, including White Technology parts or any other discontinued range, bring the part number to us and we can advise on what is possible. This topic was covered in depth in Force Tech Talk Episode 12, available on our website and YouTube channel.