BGA socket allows RAM upgrades on SBCs

In most cases, both the eMMC flash and RAM are soldered on single board computers, but we’ve previously boards with eMMC flash modules that allows to optionally add storage of various capacity and speed. But today I learned something similar exists for RAM chips with a socket that allows you to clip a BGA chip to change RAM capacity.

The BGA socket is simply soldered on the board instead of the RAM chip itself, and as demonstrated on the MangoPi MQ Pro board, you could then insert the chip on the board instead of soldering it.

BGA RAM socket / Interposer

Those are the specifications of the “DDR3x16-96” socket used above:

  • Materials
    • Socket base: LCP (liquid crystal polymers)
    • Contacts: BeCu (Beryllium Copper), selective Au-Au flash over Ni plating
  • Insulation resistance – 1000 MOhm or more at DC 100V
  • Dielectric withstanding voltage – 100V AC for one minute
  • Contact resistance – 50 mOhm max, at 10mA and 20mV max (initial)
  • Operating temperature – -50°C to +150°C
  • Life span – 10,000 times (mechanical)
  • Operation force – < 2.0 kg max

You’ll find the PCB pattern and those specs on the PDF document released by MangoPi. It appears the socket is designed to go through several insertion/removal cycle with a 10,000 times life span, but it’s unclear how hard is it to remove. But once inserted, it looks firmly in place.

This type of socket has a name, as Tom Fleet explains on Twitter, it is called an “interposer”, and one of the main manufacturers of such sockets is Samtec. The model used in the board is “JRS DDR3x16-96” according to the PDF released by MangoPi, but I was unable to find it anywhere.

While it looks neat, I’m not convinced we’ll see barebone single board computers where users can insert their own eMMC flash and RAM any time soon, since it would likely add to the overall costs. A more likely use would be for board vendors wanting to test RAM chips from various vendors and of different capacities.

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17 Comments
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Willy
Willy
5 months ago

This is awesome! I don’t understand what manages to keep the chip in place though.

I don’t imagine seeing this on SBCs any time soon either, because right now most of them just hard-code the DDR timing parameters in a blob provided with the boot loader. Supporting various timings requires more complex training code and even to retrieve the supported settings from an I2C flash that’s usually found on the memory stick. In this case it’s simpler for the board’s maker to use a SODIMM socket and suggest the customer to buy their own RAM sticks.

WereCatf
WereCatf
5 months ago

Yeah, I don’t see these ever becoming popular, but….that doesn’t stop me from wishing they did! Would be quite frankly wonderful to be able to easily swap the RAM-chips out on some of my old SBCs for bigger ones, even if it also required flashing an I2C EEPROM with new settings for them.

I’ll have to remember these sockets, so I can at least use them in my own designs.

tkaiser
tkaiser
5 months ago

> In this case it’s simpler for the board’s maker to use a SODIMM socket

Since you are speaking of ‘board’… which kind of SoC or CPU should go on that board then?

At least those from the ‘Android e-waste’ category all lack (SO-)DIMM support for obvious reasons.

anonymoushindeiru
anonymoushindeiru
5 months ago

from the photos, it looks like the chip needs pins. pins and sockets. friction.

Echo_Hotel
Echo_Hotel
5 months ago

Given the overall amount of engineering required to select the material for each individual solder ball on a chip (yes some really do go that far) many ICs come with the solder balls already in place, sort of like pins on older chips, the socket is probably latching onto that like an old ZIF socket (old style CPU socket).

Mark
Mark
5 months ago

I wonder if this makes board manufactures lower their price, since having more SKUs doesn’t affect production ( since all are socketed )

Anonymous
Anonymous
5 months ago

I would like to see slightly larger boards with SO-DIMM slots.

Can Pico-ITX fit 2x SO-DIMM slots? I found a few with only 1, but they should be vertically stackable…

zmlopez
zmlopez
5 months ago

I’ve found the JRS manufacturer web:

http://en.icsocket-jrs.com/wproducts_content-164128.html

But there aren’t more information there.

Pete
Pete
5 months ago

I’d expect to see this appear on user-serviceable electronics such as Fairphone.

Right to Repair legislation might incorporate replaceable RAM.

tkaiser
tkaiser
5 months ago

Yeah, already looking forward to Fairphone users setting up a VM for an antique OS environment to be able to install the SoC vendor’s BSP to adjust the DDR timing parameters or to tweak memory timing algorithms to finally compile a new firmware BLOB. But maybe Fairphone uses a SoC where DRAM initialization is open sourced so it’s just fiddling around in u-boot?

The average DDR chips lacks SPD and the average ‘Android e-waste’ ARM SoC lacks capabilities or even contacts to make use of SPD and as such SO-DIMMs aren’t possible as well.

Theguyuk
Theguyuk
5 months ago

What’s needed is a high speed extend bus SDcard that can run at full board memory speeds.

Click it in fit heatsink off you go . A very small SSD.

WereCatf
WereCatf
5 months ago

That would be pointless. Sure, SD Express does support 4xPCIe-lanes in an SD-card package, but that’s just the bus — it says nothing about actual achievable read/write-speeds, latencies or sustained performance. Besides which, those cards would cost a fricking arm and a leg!

No, if you want a small SSD, an M.2 NVMe is BY FAR a more realistic option.

Theguyuk
Theguyuk
5 months ago

That’s what’s Bios and standards are for .

David Willmore
David Willmore
5 months ago

I’ve worked with Samtec before and they’re a great manufacturer. We needed a custom socket for a hobby project (500to 1K volume) and they had factory engineers call me to work out the specs. We ended up buying them as well. Probably the second best support after Microchip.

Jake
Jake
5 months ago

I don’t understand how ram will help my small block Chevrolet

Jens Bauer
Jens Bauer
5 months ago

I will be using these sockets in my designs.
It’ll definitely make it easier and quicker to test several types of RAM.
However, I may even switch out ICs on SBCs I already purchased, in order to upgrade the RAM (definitely something one will want on a Raspi, unless it’s located in a shaking environment).

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