Clock Chip Modification Service Thoughts \ VOGONS

Clock Chip Modification Service Thoughts

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First post, by i486_inside

Posted on 2017-07-14, 17:17

i486_inside Offline

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Joined: 2013-10-09, 17:56

I've been looking into long term solutions for replacing DS12887/12C887/M48T86/BQ3287 and similar chips, the alt12887 project is a great Idea but at low volumes the components to build it are quite expensive and it still requires assembly, I was thinking about buying a small table-top cnc mill, coming up with a little fixture to hold the clock chip and setup a program to cut away the encapsulation epoxy to expose the battery pins and cut the leads from the existing battery and also route some channels in the epoxy to cleanly lay wires to a CR2 battery holder. Once I get everything soldered into place I could then epoxy the battery holder in place and then cover over all the area I milled out with epoxy and make it look nice. I'm thinking of using a CR2 battery because the holder should fit nicely on the top of the chip and would provide much greater capacity that a cr1220 coin cell which is about the largest coin cell you can put on top of the chip before it sticks off the sides a lot.

The proposed BOM (*Amortized on 100 units):
DS128(8)7(A)(+) ~$2
CR-2 Holder: ~$1.5
CNC Mill*: $4
Wire*: ~0.20
CR2 Battery:~$2

So If I were to try to do a 100 Unit run I could make them for about $7-8/piece or ~$10 if the battery is included. Which means I could sell them pre-modded for ~$15 shipped per chip.

Right now this is just an idea I have, let me know your thoughts.

Reply 1 of 2, by SSTV2

Posted on 2017-07-15, 01:15

SSTV2 Offline

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That service would be perfect for extremely lazy people, all it takes to expose RTC IC is a simple hairdryer and a pair of pliers, the result looks something like this:

Reply 2 of 2, by i486_inside

Posted on 2017-07-15, 04:12

i486_inside Offline

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Posts: 167
Joined: 2013-10-09, 17:56

I thought of a better way to do it, I could get 100 DS12885 DIP-24 chips from alliexpress for $120 with fedex shipping, then it is about $260 from mouser to buy 100 6pf 32.768khz oscillators, 24 pin dip sockets, and cr-2 battery holders

Which makes it out to be about $4 per unit plus the cost of epoxy.

The reason that I include a dip socket is that I think it could be used to help hold the oscillator leads in place before soldering. Although it may be a better Idea just to buy the smt version of the oscilator and glue it into place on top of the chip before soldering, with the SMT oscilator and without DIP socket that would shave $0.50 off the production cost. Although I'm still not sure whether I would prefer the oscilator to stick straight up beside the battery or mount the oscillator on top of the chip and then I would have to use a thick layer of epoxy or something to shim between the chip and the battery holder.

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