Bubble 7110A Ready For The PCB Fab House

A project log for Magnetic Bubble Memory Makes a Comeback

An Old Attraction to Magnetic Bubble Memory leads to a 1Mbit Board for the SBC-85, 8085 based single board computer

craigCraig 04/24/2020 at 03:170 Comments

The first “real” version of the SBC-85 1 Mbit bubble board is about ready to go to the fab shop so they should arrive back here mid May.  The 7110A is the 20-pin version of the bubble, not the leadless version that requires the carrier used in the prototype board.   Since the 7110A version can be found for sale much much more frequently than the leadless 7110, AND because the Molex carriers do not exist anyway, AND because the board needed room for more bulk storage capacitance to meet the power off voltage decay rates, version 1.1  is designed around the 7110A bubble.  The 7110A is functionally equivalent to the original 7110, just Intel’s “updated” packaging.  

The 20-pin 7110A followed the release of the 4 Mbit bubble which was only ever released in the 20-pin version.  As a matter of interest, the original leadless 7110 package was released as a stopgap because they were having technical issues with the epoxy injection moving / destroying the bonding wires.  The problem was solved when they went to a newer low pressure over-molding technique for the 20-pin 4Mbit, and the same process was used shortly afterwards on the 20-pin 1Mbit.

Once I get the new board in and have completed the first round or two of testing, the bare boards will be ready to send to a handful of testing partners who have the rest of the SBC-85 hardware, components, and ability to do the testing.  Let me know if interested.

The photos are of the new board, a 7110A 20-pin 1Mbit bubble, and the BPK70A bubble kit.