IC sockets in aviation equipment

:A friend has asked me to look at a 30-year old aviation radio that :he's had serviced in the past. At that time the technician sprayed and :reseated the various IC sockets. I don't yet have the radio, but I'm :thinking that IC sockets would be an unreliable thing to have in any :aviation application. Does anyone know what the rules are today? BTW, :my understanding is that this radio is a backup that is going into a :privately built aircraft. : :- Franc Zabkar

Franc, I think the equipment design would be covered by Civil Aviation Authority regulations such as

While there does not appear to be a specific design requirement excluding the use of IC sockets in such equipment, paragraph 2.10 specifies that the equipment must continue to be fully operational under conditions of severe vibration and shock. I think you will find that in order to meet this criterion, aviation radio manufacturers do not use sockets unless they are absolutely necessary since the probability of unseated devices would be high. Where a socket is required it will be of a high reliability type and the component will be firmly held in by use of mechanical clamps or other means.

Authority

equipment

cable ties. work great with machine-screw sockets.

Cheers Terry

I would never use sockets, ever. Sockets are bad, and are never good. Even in parts that are susceptible to damage they are bad. Sockets will always let you down. How a piece of aviation gear can be approved with sockets is beyond me.

Did I mention that sockets are bad?

Then explain the use of IC sockets aboard the International Space Station's communications systems. I know they are there, because I built the radio that was part of the Lockheed-Martin KU band system.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Depends on the socket. The old Augat sockets with machined pins were excellent - nothing would shake an IC out of them but some of the cheaper ones weren't so robust.

Alan

Franc Zabkar wrote:

On Thu, 21 Feb 2008 16:20:51 +0000, Alan Peake put finger to keyboard and composed:

I've seen one printer design where the IC was retained in a machine socket by soldering the power pins of the IC to the respective pins of the socket.

- Franc Zabkar

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Please remove one 'i' from my address when replying by email.

Give me a good reason why? I used to love fixing those boards that would come in with the super high quality never fail sockets. Flex the board and reseat the socket, $500bucks thanks.

It's not so much the chip falling out, its mainly corrosion causing bad connections. 30 years ago chips were expensive and less reliable, they were socketed to facilitate replacement especially during factory test. These days there is no reason to socket any unless they contain firmware that may need to be updated.

The reason for using sockets? They ordered a customized version of our standard telemetry receiver. The software for the control panel, the tuner, and the demodulator was custom for each customer. One mistake a lot of people make is using different metals for the IC pins, and the sockets. A lot of these units were used in VERY remote locations, so the firmware was socketed, for field upgrades. No one wants to ship a piece of equipment in for a minor upgrade.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

On Fri, 22 Feb 2008 20:57:33 +1000, The Real Andy put finger to keyboard and composed:

I now have the radio, a Narco COM11A, probably built in 1972. The IC sockets appear to be high quality AMP types but they have all fatigued. One is so bad that the IC springs out of one side of the socket without me even touching it. The radio was serviced in Sept

2007 but obviously not properly. I plan to solder all the chips (Fairchild 9000 series TTL logic) directly to the PCB wherever possible. Elsewhere I'll use turned pin wire wrap sockets (for interconnecting two PCBs).

- Franc Zabkar

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Please remove one 'i' from my address when replying by email.

The old Augat sockets had "square peg in round hole" for the IC legs going into the Augat socket.

This worked as well as wire-wrap joints in that it formed a molecular bond between IC leg and socket hole that was quite reliable.

I can remember environmentally testing Augat socketed PC boards with very severe vibration and temperature variations. Never had a single problem with IC-socket connections.

Ross