1.778mm DIP spacing - what was this used for? - Page 1
Forum section: electronics / beginners

author: JoeN
author_rank: Frequent Contributor
timestamp: June 16, 2016, 10:37:39 pm
content: I just got into electronics seriously in 2012 and I just ran across something I have never seen before. Apparently there were 1.778mm spaced DIPs for some applications. It looks like it never caught on. I found out about this non-standard spacing looking for ZIF sockets on eBay and discovered this:http://www.ebay.com/itm/401115647481After doing some research I find that Digikey sells sockets like these, probably very old stock. I can't find any components in this pin pitch, though, a few more sockets on eBay and Digikey, but zero actual components:http://www.ebay.com/sch/i.html?_nkw=1.778mmWere there actual 64 pin devices made in this pin pitch? What was it used for? Anyone have a history on 1.778mm pitch packaging?Just curious. Thank you.

author: bitslice
author_rank: Frequent Contributor
timestamp: June 16, 2016, 10:52:49 pm
content: There was a bunch of VDU processors like the V9958 that used 1.778mm spacing, hence the supply of suitable sockets (Shrink Plastic Dual In-line Package (SPDIP))Probably a halfway house to flat packages

author: Ian.M
author_rank: Super Contributor
timestamp: June 16, 2016, 10:59:39 pm
content: Probably get more results for: 0.07" pitch shrink DIP package.I've seen that package before in some '90's consumer entertainment gear, but they weren't exactly common and AFAIK are obsolete due to the rise of surface mount technology.N.B. 'SPDIP' is more commonly used nowadays for Slim PDIP - 24 or 28 pin package with 0.3" width rather than 0.6". e.g. Microchip commonly use 0.3" wide 0.1" pitch SPDIP for their 28 pin devices.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 16, 2016, 11:11:16 pm
content: Shrink-DIPs were popular for consumer electronics where they wanted a high pin count on through-hole PCBs.Mitsubishi did a lot of their 6502 based MCU family in this package - ISTR 64 pins.ST also did some ST7 parts -http://www.digikey.co.uk/product-search/en/integrated-circuits-ics/embedded-microcontrollers/2556109?k=st7&k=&pkeyword=st7&pv16=8678&FV=fff40027%2Cfff800cd&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=250I think shrink-DIPs died out as surface mount became more widely used.Digikey shows only 4 out of 64 listed Shrink-DIP MCUs in stock

author: McBryce
author_rank: Super Contributor
timestamp: June 17, 2016, 09:34:18 am
content: The rather famous Commodore 64 used one on one of the later cost reduction models. You can see the 64 pin IC in this picture with 1.778mm pitch:http://ist.uwaterloo.ca/~schepers/MJK/pics/c64pcbr4a.jpgMcBryce.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 17, 2016, 11:14:52 am
content: Here are a few in my box of random old MCUs

author: McBryce
author_rank: Super Contributor
timestamp: June 17, 2016, 11:38:15 am
content: I don't think I've ever seen sockets for these though? Were there ever sockets available?McBryce.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 17, 2016, 12:02:22 pm
content: Yes, there were both turned-pin and stamped sockets

author: JoeN
author_rank: Frequent Contributor
timestamp: June 17, 2016, 08:26:16 pm
content: Quote from: McBryce on June 17, 2016, 11:38:15 amSecond ebay link in my original message above has quite a few sockets. Some are still available at Digikey, probably very old DCs.http://www.ebay.com/sch/i.html?_nkw=1.778mmThanks to all who replied, especially Mike who took images of his IC collection. I never saw sockets for double-row DIPs before. I figured those ICs just got soldered in.

author: German_EE
author_rank: Super Contributor
timestamp: June 18, 2016, 07:32:22 am
content: The weird thing is that I can't find a conversion for 1.778mm to inches. I can't see anything between 1/16 inch (1.5875mm) and 5/64 inch (1.9844mm)

author: JoeN
author_rank: Frequent Contributor
timestamp: June 18, 2016, 07:44:34 am
content: Quote from: German_EE on June 18, 2016, 07:32:22 amYou are thinking like a carpenter. It's exactly 0.07", which is what they were going for, just a tighter pitch than 2.54mm. There are a lot of non-fractional pin pitches out there - 0.8mm, 0.65mm, 0.5mm, etc. As far as I know, only 2.54mm (whole tenth of an inch), 1.27mm (1/2 of a tenth of an inch) and 0.635mm (1/4 of a tenth of an inch) seem to have been set up to convert into something that you can think of as fractional inches nicely.

author: SeanB
author_rank: Super Contributor
timestamp: June 18, 2016, 10:52:01 am
content: Oh yes, the (in)famous QIL package. much loved as you could get almost the density of PLCC in a plastic package that would still be usable by regular auto insert machines. Of course once inserted and soldered they were almost impossible to unsolder, especially on SRBP boards where they often were used, as they would gladly peel off the copper pads.I just used to clip all the leads, or run a sharp brand new Stanley knife blade down the edge a few times, till I was through all the leads, then do the same the other side and unsolder each stub individually. Never saw the sockets they had there Mike.