Re: IC Sockets

Ken KM4NFQ
 

Hello Bob, K5MYJ,

Where do you find your SMD IC to DIP adapter boards?
The ones I have found are way more expensive than the chip, for example:
https://www.digikey.com/products/en?mpart=PA0168&v=315

Regards,
Ken, KM4NFQ "Not Fully Qualified"

On Tue, Jul 23, 2019 at 11:27 AM Bob Macklin <macklinbob@...> wrote:

BTW:

When I am forced to use surface mount ICs (SSOP) I use SSOP/DIP adapters. Then these adapters can plug into normal IC sockets.

I can mount chips that have 50mil pin spacing but the finer ones like TQFP give me more problems. But I have adapters for them also.

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"



----- Original Message -----
From: Hans Summers
To: QRPLabs@groups.io
Sent: Monday, July 22, 2019 11:22 PM
Subject: Re: [QRPLabs] IC Sockets

Hi all

The reason the QCX does not have sockets for all ICs is NOT to do with RF issues such as inductance caused by increased lead length. I did mention this in my opinion, on page 10 of the manual:

"Some people like using IC sockets, some don’t. Undoubtedly there is a cost impact, of course. Personally, I believe that on average, the use of IC sockets causes more problems than it solves. They create the potential for bent pins that don’t make contact properly, hidden shorts under the socket, issues with increased lead length, etc. Accordingly, the remaining ICs are soldered directly into the PCB without IC sockets. Please forgive me if you disagree."

But intended that as a general opinion about IC sockets; in the QCX, lead length is not a problem.

This effect DOES occur, but is not important in the QCX; the inductance of a 1mm diameter wire, 10mm long is 6nH. For an IC in a socket, the effective increase in lead length is the increased height at which the chip now resides, relative to the board. I just measured a low-profile turned-pin machined IC socket here, and that parameter in this case is 4.7mm. So, about 3nH per IC pin. But at the frequencies QCX operates, 3nH is of no significant consequence. PCB traces also have comparable length anyway. It is even more negligible, in the case of the op-amps which operate at audio frequencies. In some applications 3nH would be important and must be eliminated or accounted for in the design. But not QCX...

As Alan said, the probability of an op-amp failure is very low; I cannot recall a case of an op-amp failing. It is relatively easy to damage the microcontroller IC2 and even the Si5351A IC1. Yesterday while undertaking a repair of someone's QCX, I did find myself wishing the Si5351A was socketed :-/ But I managed the replacement in the end. IC3 (74ACT00) has also been known to get damaged sometimes, as has IC4 (FST3253). Unfortunately you can't socket IC4 either. But anyone who wants to socket IC3, can if they want...

In my experience that led to my opinion on sockets, they seem to cause more issues than they solve, on average. My issues are with bent pins, poor contacts, hidden things under the socket, etc.

I have no doubt some of these issues could be eliminated or mitigated by the use of military spec machined-pin IC sockets. But that would also grossly adversely affect the cost of the QCX. There doesn't seem to be enough justification to do that in the production; but an individual constructor is welcome to do so if he so wishes.

Many construction faults in the QCX occur in the audio stages. I do think worrying about socketing the op-amps or not, is leading focus away from the true path to salvation. Component failures are very rare. It is far, far more likely that you made a soldering mistake. Dry joints, damaged a track, put a component in the wrong way round, mis-read a component value, etc. It's tempting to want to assign blame elsewhere (bad components)... but not fruitful. I'm starting with the man in the mirror...

73 Hans G0UPL
http://qrp-labs.com

On Mon, Jul 22, 2019 at 11:48 PM Bob Macklin <macklinbob@...> wrote:

Sockets were used for tubes all the way up to 10KMC (10GHz)

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"

----- Original Message -----
From: Jim Mcilroy via Groups.Io
To: QRPLabs@groups.io
Sent: Monday, July 22, 2019 8:49 AM
Subject: Re: [QRPLabs] IC Sockets

Hi

On this occasion I used sockets for these AF chips as I had a stack of them in the components box. I tend not to use sockets for RF chips though. Each to their own.

It could be an advantage for faultfinding in this design but my QCX40 worked first time.

I've never experienced ICs walking out of sockets, however I do recall speaking to someone years ago who worked in a power station and told stories about nuts loosening on busbars and having to check components here and there.

Jim

On 22/07/2019 15:22, Alan de G1FXB via Groups.Io wrote:

Hi Gerry,
Easy answer is just do whatever you are most comfortable with.

Every interconnection is a potential point of failure if you use the best type you can, you can mitigate the risk.
It's sometimes easy to accidentality bend a pin, if it bends outwards it's obvious, less so if it folds underneath.
Sometimes IC's can walk out of sockets.

I don't think anyone has bad IC's from manufacture, i don't recall anyone has managed to blow up any opamps.
IC3 can be damaged through failure elsewhere.
Perhaps there is value in socketing this one?


Alan

On 22/07/2019 14:53, Gerald Ball via Groups.Io wrote:

At the moment I am waiting, with some excitement, for a 20m QCX. in the meanwhile I am reading the manual and understand that there are a number of IC's which are to be soldered directly to the printed circuit board. Does anyone have experience of mounting these IC's in Sockets. Apart from extra production cost, I can't see any technical reason for not using sockets. The main advantage of course being one of future fault finding. I would appreciate your comments on this.?
--
gerry

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