Do you fit IC sockets when replacing an IC?

[Craig Sawyers]

Originally Posted by David G4EBT

Instead, snip off each of the pins, then using forceps attached to each pin in turn, melt the solder on the underside of the board and gently pull out the pin.

Er - wasn't that what I said?

I'm pretty sure I bought my forceps from Rapid, but either I'm remembering wrong, or they no longer stock them.

[G6Tanuki]

We had a couple of "Weller-style" high power solder-guns fitted with ~desoldering slabs~ for quickly removing failed DIL chips. A brass block with two grooves machined in it, spaced so that all the 'legs' of a chip-to-be-removed fitted into the grooves.

Clamp the board chip-side-down. Put a thin strip of special heat-resistant PTFE tape in the gap between the two rows of chip-pads to be unsoldered.

Grab the desolderer. Pull the trigger and wait for 10 seconds or so for it to get hot. Then press the brass 'slab' against the offending chip's underneath..

Wait 5 seconds or so, remove the desolderer and give the board a sharp tap. The offending chip should then drop out.

If you were really quick, you could then blast the area round the removed chip with compressed-air which would blow the residual solder out of the holes from which the failed chip had been evicted before it solidified again.

"Book time" to unsolder a 16-pin DIL chip and clean up the holes in the PCB ready for refitting was - if I recall - something like 6 minutes. A skilled operator could do it in 40 seconds.

[evingar]

Horses for courses.

I recently repaired a hideously intermittent Farnell bench PSU, the fault was traced to tin plate socket. Other IC's inside had partially worked their way out of their sockets and there was evidence of corrosion on the IC legs and socket pins. I reckoned it was only a matter of time before other intermittences occurred, so I removed all the sockets and soldered everything directly into the PCB.

However, in the "day job", I had sync output on a pulse generator fail. I fitted the replacement IC in good quality "turned" IC socket. IMHO it's always worth considering socketing devices that drive signals or ports out of equipment, especially when past experience has shown the drivers to be vulnerable. If vibration is likley to be an issue, then you can always solder a couple of pins into the socket of a turned type (say pin 7 and 14 of a TTL IC).

Bottom line, personally, I wouldn't advocate fitting sockets "willy nilly" (unless prototyping) as any mechanical device is a reliability weak point.

[Outrun_uk]

If the IC in question is cheap then solder straight in otherwise a socket is fitted until the device is proven working then either leave as-is or take the socket out and solder working replacement IC in. I have had a few occurrences of new components being faulty which has resulted in lots of head-scratching though...

[bluepilot]

Originally Posted by David G4EBT

snip off each of the pins,

The problem with that is that sometimes the pin twists around as you cut it. Then it can twist the track off on the other side of the board. On the other hand, heating the pins too much can unstick the tracks from the board. Whatever method you use to remove the chip, I prefer to replace it with a socket. On the one hand the chances of a future bad contact increase. On the other hand, that is easily mended with a bit of "honeymoon maintenance", unlike removing the chip again.

[Biggles]

I have never generally bothered with sockets, and just risk soldering directly when building something. I have been lucky so far, apart from the odd one, caused by me not paying attention and having to desolder a wrongly orientated chip or the like. I do use one at work for plugging large controller chips in to test them on a piece of equipment but apart from that I generally avoid them. Probably because it adds extra cost to whatever I am doing.

[McMurdo]

For further reading about the reliability testing of instruments used in helicopters and granny's front room I refer you to the book 'Ekco Sounds'.

I've had problems with pressed style sockets in Hameg scopes. It can also affect PLCCs and anything in an aggressive atmosphere. Thank goodness 50's TVs dont use them.

[Terry_VK5TM]

Back in the 80's, working for Rank-NEC, the most common problem on the then near new TV chassis was the IC socket holding the Chroma and associated function IC.

Factory orders were to remove the socket and solder the IC in directly.

On that basis, unless it is prototyping/homebrewing or things with socketed Eproms etc, I don't use ic sockets.

Terry