Memory Components Glossary

Plain definitions of the terms used when buying refurbished memory components. See also the FAQ and how to read part numbers.

AVL (approved vendor list)

A list of components or suppliers approved for use in a product design.

Allocation

A supply situation in which a manufacturer rations parts among customers instead of filling all orders, common during shortages.

BGA (ball grid array)

A chip package whose connections are an array of solder balls on the underside. Most DRAM, eMMC and LPDDR devices use BGA packages.

Burn-in

Operating devices under electrical and temperature stress for a period so that early failures show up before shipment.

Certificate of conformance

A supplier document that states a product meets the stated specification or order requirements. Ask what it covers and who signs it.

Counterfeit and mislabelled parts

Parts that carry false markings or are not what the label says. Part-number matching, date-code checks and testing reduce the risk.

DDR (double data rate)

A family of SDRAM that transfers data on both clock edges. Generations include DDR3, DDR4 and DDR5; they are not electrically interchangeable.

DDR3L

The low-voltage version of DDR3, running at 1.35 V instead of 1.5 V. Compatibility with DDR3 depends on the controller and board.

DRAM / SDRAM

Dynamic random-access memory. SDRAM is synchronous DRAM, whose operation is timed by a clock signal. DDR, LPDDR, GDDR and HBM are all SDRAM families.

Date code

A marking that shows when a component was manufactured, normally as a year and week. Mixed date codes in one lot can be a warning sign.

Density and organization

Density is the total bits per device (for example 4 Gb). Organization shows depth and data width, for example 512M x 8 is 512 Meg locations of 8 bits.

EOL (end of life)

The manufacturer has announced it will stop making a part. Supply then depends on remaining stock and the secondary market.

ESD

Electrostatic discharge. Memory devices are packed and handled in ESD-safe materials to avoid damage.

Electrical test

Checks that a device has no opens or shorts, can be written and read, and, where the device type allows, meets its speed requirement.

GDDR

Graphics DDR memory, optimized for bandwidth in graphics cards and accelerators.

HBM (high-bandwidth memory)

Stacked DRAM placed next to a processor in the same package, used in AI accelerators and high-performance computing.

J-STD-033

The JEDEC/IPC standard for handling, packing and shipping moisture-sensitive surface-mount devices.

LPDDR

Low-power DDR SDRAM for mobile and embedded devices. LPDDR4, LPDDR4X and LPDDR5 differ in speed and I/O voltage.

LTB (last-time buy)

The final window in which a manufacturer accepts orders for a part that is being discontinued.

Lot code / lot record

An identifier that ties a batch of parts to its inspection and test records so any part can be traced.

MSL (moisture sensitivity level)

A rating from the JEDEC J-STD-020 standard that says how long a package may be exposed to air before it needs baking prior to reflow.

NAND flash

Non-volatile memory that keeps data without power, used in SSDs, memory cards and managed storage such as eMMC.

New, surplus, reclaimed

New parts are unused and normally come from the manufacturer or an authorized channel. Surplus parts are unused but no longer needed by a buyer. Reclaimed parts are removed from assembled boards and need the most careful verification.

Part-number suffix

The characters after the base part number that give package, temperature range, speed or revision. Two parts with the same base number can differ by suffix.

Reballing

Replacing the solder balls on a BGA package so that it can be soldered to a board again. Done with controlled temperature profiles because excess heat can damage the device.

Refurbished memory

A memory component that was previously installed or held in stock and has been inspected, restored where needed and tested before resale. It is not the same as a part that was only removed from a board and remarked.

Speed grade

A code or number that shows the rated data rate of a part, for example -062E on a Micron DDR4 or -046 on a Micron LPDDR4X.

UFS

Universal Flash Storage: a faster managed NAND storage standard used mainly in phones and automotive systems.

eMCP / uMCP

Multi-chip packages that combine managed NAND (eMMC or UFS) with LPDDR in one package.

eMMC

Embedded MultiMediaCard: NAND flash with a controller in one BGA package, used for storage in embedded and consumer devices.