I know that microSD cards are typically not designed for this type of use, but has anyone tried this? Would it be possible in production ( >1000 units), that is, would any PCBA service be able to do this for you?
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2\$\begingroup\$ I think that you'd need some kind of connector anyway since the contacts may be a little deep in plastic, moreover the uSD casing can not withstand the high temps needed to solder, so you'd probably need to go with wires... That would cost a ton. So a slot is better. \$\endgroup\$– Vladimir CraveroCommented Sep 8, 2014 at 20:15
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2\$\begingroup\$ Here is someone who reflowed a micro SD directly on a pcb: dotmana.com/weblog/2015/08/… and it looks like he sent some trays to production. \$\endgroup\$– someonrCommented Apr 5, 2016 at 10:33
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\$\begingroup\$ As shown in these Reddit links (redd.it/2v0zc3 and redd.it/3cjz32) some people have found their cheap flash drives actually have a soldered microSD card inside. I guess that count as usage "for production". \$\endgroup\$– MV.Commented May 4, 2017 at 19:17
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2 Answers
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I have soldered wires direct to an SD card before now (I needed an SD card connected in an emergency and had no suitable socket for it). It worked fine, but I certainly wouldn't choose it, or anything like it, for production.
Firstly neither the contacts, nor the housing, are designed for soldering. Yes, you can solder them, but the plastic has a low temperature melting point. That means no reflow soldering; no wave soldering; no clumsy drunken hand soldering.
Secondly, as noted in the comments, the contacts are not flush, so they would have to be soldered to something first before the whole assembly being soldered to the board (or something being soldered to the board first, etc). That is extra cost, and extra time. I am not aware of any off-the-shelf part for doing it, so you'd have to pay for the manufacturing of it, pay for it to be installed, and pay for it breaking afterwards.
You're better off using a proper SD card socket. It has the advantage that the SD card can be changed when its write cycle lifetime has expired.
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\$\begingroup\$ I see, thanks for the insight. We'll just have to bite the bullet and pay for the card slot. \$\endgroup\$– ShubhamCommented Sep 10, 2014 at 1:02
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\$\begingroup\$ 4ucon has them for $0.20 / pc in qty 1000 (item 19850). I dare say you could do better if you have an agent in Shenzhen. \$\endgroup\$ Commented Sep 10, 2014 at 4:38
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If you want the simplicity of an SD-compatible interface, you can get what is essentially an SD card on a chip: http://www.samsung.com/global/business/semiconductor/product/flash-emmc/overview
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\$\begingroup\$ OP is building 1000 units, so I doubt that they'll be hand-soldered. Not that hand-soldering a BGA is particularly challenging.. \$\endgroup\$ Commented Sep 9, 2014 at 1:16
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\$\begingroup\$ ... Hand soldering a bga, not challenging, yea right... Also, not my point. You want OP to go from thinking about a 8 pin card to a 153 BGA. The former requiring minimal pins and processing, the latter undoubtedly requiring excessive routing and MULTIPLE LAYERS. That is not the simplicity of an SD-compartible interface. \$\endgroup\$– PasserbyCommented Sep 9, 2014 at 1:56
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1\$\begingroup\$ Did you look at the ballouts? It's mostly no-connects, power and ground. Could readily be routed on a 2-layer board. Smaller than a microSD socket. \$\endgroup\$ Commented Sep 9, 2014 at 3:08
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1\$\begingroup\$ Sounds like a great solution if you need larger amounts of memory, but we need <1GB. This maybe too expensive for us, but thanks for pointing this out, it will be good to consider in future designs. \$\endgroup\$– ShubhamCommented Sep 10, 2014 at 1:04