Is there any point socketing every DIP chip on a board? - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: October 25, 2017, 09:31:05 am
content: I have a project that involves a bunch of DIP and one PLCC chip. I am wondering if I should socket all of them. I know that socketing chips allows them to be removed or replaced down the road. Is there any obvious drawbacks?I don’t expect mechanical stress or vibration in normal operating conditions, and during shipping the chips are not plugged into the board (ships as unassembled kits by default)

author: Mjolinor
author_rank: Frequent Contributor
timestamp: October 25, 2017, 09:49:17 am
content: Chip creep. Not a good idea to socket things unless you think they will need replacing. Time will make the connection high impedance and the chips creep slowly out of the sockets.

author: coppice
author_rank: Super Contributor
timestamp: October 25, 2017, 09:54:39 am
content: Quote from: Mjolinor on October 25, 2017, 09:49:17 amCreeping out of the socket is unusual. However the flat blade type of socket pins are really good at wearing away the IC's legs in a high vibration environment. Only use the tubular pin type of socket if there is a lot of vibration and you really must socket.Generally socketing ICs that don't obviously need to be exchanged (e.g. things that need to be taken out to be reprogrammed) is a dumb idea. It just reduces reliability.

author: daqq
author_rank: Super Contributor
timestamp: October 25, 2017, 10:03:40 am
content: Well, there is additional height, possible extra vibration problems, maybe a bit higher resistance, additional material on which you can have some thermal voltages, but nothing particularly nasty.

author: Mjolinor
author_rank: Frequent Contributor
timestamp: October 25, 2017, 10:04:30 am
content: Yup my bad. I didn't mean out as in falling onto the PCB but socketed DIPs are never all the way home and often just a push will fix some faulty equipment.

author: technix
author_rank: Super Contributor
timestamp: October 25, 2017, 10:39:20 am
content: I don’t expect the board to vibrate, but being part of a dev kit I do expect frying chips.

author: ElektroQuark
author_rank: Unknown
timestamp: October 25, 2017, 11:55:14 am
content: Quote from: technix on October 25, 2017, 10:39:20 amDecided then. Use sockets.

author: David Hess
author_rank: Super Contributor
timestamp: October 25, 2017, 01:02:33 pm
content: Manufacturers stopped using sockets and soldered DIPs into the boards once sockets became less reliable than DIP ICs. During development, I use sockets where possible and may socket other parts like transistors and passives and I wish PLCC (plastic leaded chip carriers, the ones with the J-leads) were more popular. For production, I use them for ICs which are likely to be less reliable like I/O expanders and buffers which are exposed to ESD.

author: eugenenine
author_rank: Frequent Contributor
timestamp: October 25, 2017, 01:23:02 pm
content: If it a kit use sockets. its easier to replace the "defective" socket when the end user used an 8000W soldering iron.For height mil-max used to make these socket carriers where the sockets soldered right inside the holed in the PCB then you remove the carrier and plug the IC in so it was very low profile. I haven't looked recently to see if they are still sold though.

author: brucehoult
author_rank: Super Contributor
timestamp: October 25, 2017, 01:35:07 pm
content: Apple ][ had everything in sockets.Pushing all the chips firmly into their sockets was a standard thing if it stopped working.https://www.extremetech.com/wp-content/uploads/2011/08/Apple-II-Guts.jpg

author: Kleinstein
author_rank: Super Contributor
timestamp: October 25, 2017, 04:45:09 pm
content: A socket adds a little more length and capacitance this can be an issue with high frequency parts - you might prefer SO... instead of DIP for this anyway.For a kit and kind of development board I would definitely prefer sockets, as a fault is not that rare and less damage during soldering (more ESD than heat).I also prefer sockets for my own boards - they make testing and replacement easier. It also prevents damage to the board from unsoldering parts.

author: Buriedcode
author_rank: Super Contributor
timestamp: October 25, 2017, 05:21:38 pm
content: As you can tell form the replies here (which are quite diverse!)... depends.-Dev boards/evaluation boards where there is a real risk of something frying? yes.-Dev boards/evaluation boards that support multiple devices? yes, obviously.-Where boards are easily accessed, and certain parts have a reasonable chance of failing? (like transistor drivers, power drivers etc..) yes.-Your own boards where the devices are somewhat expensive or hard to obtain and you may wish to 're-use' them in another project? yes.-Although a bit dated now, since most uC's have plenty of EEPROM. Sometimes it is easier to just socket an EEPROM or flash rather than provide the facility to update it. yes.-Cheap logic hidden away in a board whose inputs and outputs are directly exposed to external connectors.... naaOf course we're talking DIP devices here, so things like 'current capability' is a moot point since I haven't seen DIPs with several pins for the same signal used for current - DIP just isn't the package for it.Also, the sorts of switching frequencies (or should I say.. rise/fall times) that DIP packaged IC's generally go up to isn't really a big deal with the added capacitance of a socket, so again, moot point. (unless you can find a DIP 1GHz device? you might, I don't know!)With all that said, there has bone occasion where I wish I had. Mechanical strain/flex on the board 'cracked' CMOS logic devices, desoldering them was a pain. I was unaware a customer would be clamping the enclosure with such force as to crush the aluminium enclosure, and bend the PCB inside.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 25, 2017, 05:37:15 pm
content: Extremely powerful way to tell your customer segments that this is designed in 1990's, "for hobbyists", by a designer who's completely clueless about anything related to electronic engineering.No technical point, expect to increase failure rates somewhat, to get that nice "any hobbyist can fix this broken shit by replacing all the ICs that have actually developed contact problems, and feel like they are great technicians".Sometimes all of this is desired for the right "feeling".Preferred for the final touch: autoroute in Eagle, including ground traces as standard signals. Don't use power bypass caps.Also commonly used in audiophoolery things.

author: technix
author_rank: Super Contributor
timestamp: October 25, 2017, 05:58:22 pm
content: Quote from: Siwastaja on October 25, 2017, 05:37:15 pmWhat about debug access, especially on a board where chips that require high voltage programming is involved or lacked in-system programming capabilities? Especially when before a bootloader is ready? (In my develop process the bootloader is almost always based on a stripped down version of the main application code, thus always comes after the main code is written.)

author: Siwastaja
author_rank: Super Contributor
timestamp: October 25, 2017, 06:00:58 pm
content: Add necessary connectors and test points for programming and measurement.This thing called "in system programming" came in the late 1990's exactly to solve the DIP socket catastrophe for programmagle parts.I fail to see how socketing a component eases measurement. For that, you need test points. Usually, a simple marked via is enough, but you can of course use any connector you like (a standard 0.1" pin header pin is fairly good).I don't know about any even remotely modern part that lacks in-system programming capability. An example?It sound like you have catastrophical design issues going on, which you are trying to fix by using DIP sockets. Post you schematic and you'll get help on the issues. I'm sure that in most cases there's a better way. If you are considering socketing each and every IC, then each and every case must be analyzed to find the issue you are having with it, and why you think it's going to be solved with a socket.

author: technix
author_rank: Super Contributor
timestamp: October 25, 2017, 06:05:34 pm
content: Quote from: Buriedcode on October 25, 2017, 05:21:38 pmHere is an RF DIP-8 for you:http://pira.cz/pdf/sa612.pdfWell on NXP's modern datasheet DIP-8 is deleted, but the chip in DIP-8 is still fairly abundant in second source manufacturers.

author: technix
author_rank: Super Contributor
timestamp: October 25, 2017, 06:19:25 pm
content: Quote from: Siwastaja on October 25, 2017, 06:00:58 pmDo you have a list of likely reasons for the catastrophical design issues? I do understand the ISP part, but somehow for some reason on some platform it is quite hard to achieve.A quick example is that it is almost impossible to source AT89S or AT89LE series 8051 chips in China, while the STC parts lacked a working external bus where this project actually needs. So for my specific 8051-based idea I am locked into the HVPP-only AT89C line.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 25, 2017, 06:30:18 pm
content: Some that come in mind:1) Lack of the most basic protection features, instead relying on "just replace the burned parts". The issues: 1) why burn them at all? Changing them is tedious and causes downtime. 2) Often, many more parts are burned in sequence, so the number of affected parts is often large2) Lack of knowledge about the in-system programmability of "modern" (last two decades, basically) programmable parts3) Wrong belief that parts magically just "break down" and need to be replaced. If they break, it comes back to a design fault, just replacing them just makes the new ones break down again. These design faults can be things such as:- Improper bypassing causing overvoltage spikes due to parasitic inductance, killing the parts in overvoltage (easy to do when autorouting completely in Eagle + adding the sockets)- Improper protection of user-accessable inputs & outputs: lack of current limiting, clamping, etc. Often as easy as just a single series resistor

author: Siwastaja
author_rank: Super Contributor
timestamp: October 25, 2017, 06:34:50 pm
content: Quote from: technix on October 25, 2017, 06:19:25 pmAh, you are designing a retro thing using long obsolete parts. Then, by all means, of course you need to use the relevant technology. This means socketing these non-in-system-programmable ICs. But of course, notallICs on the board, if you don't want to give that "designed in Eagle for hobbyists in 1999 while reading Elektor magazine" look.

author: technix
author_rank: Super Contributor
timestamp: October 25, 2017, 06:40:26 pm
content: Quote from: Siwastaja on October 25, 2017, 06:30:18 pmThere is no way to protect against in-development accidents, like mistakenly blowing the lock fuse and permanently prevent the chip from ever being written again.Quote from: Siwastaja on October 25, 2017, 06:30:18 pmWhen you cannot source them they might as well be treated as if nonexistent. And when no good alternative is immediately available you are kind of forced to go the hard way.Quote from: Siwastaja on October 25, 2017, 06:30:18 pmOnce again, software accidents can happen, and it is not up to the hardware design to protect against it.This is a dev kit, and the sockets is mainly for protecting against unrecoverable software errors, and enabling the use of non-ISP but way easier to source parts, which no amount of hardware can protect against.

author: james_s
author_rank: Super Contributor
timestamp: October 25, 2017, 06:51:54 pm
content: I use sockets when I build something on perfboard, often during initial prototyping on a PCB and then only on programmable parts or parts that are likely to be damaged interfacing with the outside world. On a PCB it's very easy to desolder ICs if you have a proper desoldering tool so I don't worry too much about it. Sockets can cause more problems than they solve.

author: technix
author_rank: Super Contributor
timestamp: October 25, 2017, 06:53:46 pm
content: Quote from: Siwastaja on October 25, 2017, 06:34:50 pmNot quite a retro though, but I *need* the external bus for a Von Neumann connected 8051 bus so I can use standard 8051 monitor programs. STC does have their monitor program but that is locked onto paid or cracked versions of Keil C51, but I work on SDCC for now so that is a non-starter for me.There are five chips I intend to socket: PIC16F1455 (hard to come by in China,) AT89C51RC (HVPP-only,) AT28C256 (too complicated to ISP,) EPM7032SLC44 (maybe a chip protection trap, and I am not very good with HDL while this chip have low endurance) and IS61C256 (expensive.)At least in China when coming to MCU programming a good amount of HR's still equate this to 8051 + STM32. I can get the STM32 part down, but 8051 is new to me. Call me spoiled by the debugger but I feel poking into the memory and register of the processor a much more intuitive way of studying and debugging programs.Also for personal projects I do like the idea of being able to pull chips off after being done with it, not wasting money on died projects since chips can be repurposed afterwards.

author: mrpackethead
author_rank: Super Contributor
timestamp: October 25, 2017, 07:17:38 pm
content: Whats a thru hole part again? Been a while.... ( lol )..

author: technix
author_rank: Super Contributor
timestamp: October 25, 2017, 07:45:08 pm
content: Quote from: mrpackethead on October 25, 2017, 07:17:38 pmBeen a while too.Although I always used through-hole connectors as it is way too easy to rip a SMT connector off the board with the traces still attached, destroying the board in the process.

author: David Hess
author_rank: Super Contributor
timestamp: October 26, 2017, 03:18:03 am
content: Quote from: eugenenine on October 25, 2017, 01:23:02 pmThose are pretty expensive. I have been cutting collet socket pins out of strips or DIP sockets and soldering them in individually.