SOJ-32 package. How are they used? - Page 1
Forum section: electronics / general

author: wilfred
author_rank: Super Contributor
timestamp: March 06, 2014, 07:43:53 am
content: /.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 06, 2014, 08:20:09 am
content: PLCCs and SOJs were somewhat popular back in the day, not so much anymore I guess.You'll often find 90s computer hardware with SOJ sockets for additional RAM, because a few megs were real bucks back then(!).You still see socketed PLCCs for EEPROM/Flash from time to time, motherboard BIOSs for instance.Tim

author: kizzap
author_rank: Unknown
timestamp: March 06, 2014, 08:34:27 am
content: I think the package had something to do with people transferring to SMD over through holes. It was cheaper to modify the legs then it was to completely redo the entire chip to fit in SMD packages.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 06, 2014, 10:23:26 am
content: If you mean forming a DIP into an SOJ, the lead frame is completely different.An SOJ might be comparable to a wide-body SOIC (with extra-long, reformed leads), though I think they were usually a bit bigger still anyway?I doubt any chip was redone specifically to fit in a package. There is more than enough diversity to select from as size goes (if it doesn't fit in a TSSOP, offer it in SOIC only...), and really old designs have been shrunk many times over the years for cost reduction, not packaging (though that may be an added benefit). And that's for the few that remain in production long enough to experience things like die shrink or smaller packages.One example I can think of: LM3914 is available in PDIP and PLCC, but nothing smaller. The current (D-step) die says 2.6 x 2.4mm, which might be kind of large for a narrow SOIC (I don't know offhand what they can fit), let alone TSSOP. No idea if the size differed in previous steppings.Tim

author: poorchava
author_rank: Super Contributor
timestamp: March 06, 2014, 03:07:38 pm
content: SOJ and PLCC package were a must for all sorts programmable circuits. They are designed to allow for pre-assembly programming (in other words: in a socket) and the pin shape makes them much more resistant to bending and other damage during handling of the part. PLCCs and SOJs you can drop on a floor from a meter high and it will most likely be ok. Try to do that with QFP.Plus sockets are much cheaper and easier to manufacture, even the ZIF ones.

author: TMM
author_rank: Frequent Contributor
timestamp: March 07, 2014, 03:02:10 pm
content: The curved ends of the leads is so when it is bottomed out in a socket the stress is on the end of the pins (where they curl back and touch the underneath of the package) rather than where the pins enter the package.

author: arekm
author_rank: Unknown
timestamp: March 08, 2014, 10:52:28 pm
content: SOJ-24 socket would be useful to me ... but never saw such things, even on the internet. SOJ-24 -> something else adapters sould be also interesting.What's the best way to solder these anyway? Going to replace few soj24 memories.

author: poorchava
author_rank: Super Contributor
timestamp: March 10, 2014, 08:51:13 am
content: Quote from: arekm on March 08, 2014, 10:52:28 pmIf you're referring to the footprint, IIRC standard pitch for SOJ is the same as SOIC, but the wide body type (.3" instead of .15"). Footprint is roughly the same, probably pad length would have to be adjusted for reliable reflow. As for general soldering techniques - same as other SMT parts - tack a corner or two then solder the rest of the pins.