A good socket to use to socket resistors on a PCB - Page 1
Forum section: electronics / projects

author: SharpEars
author_rank: Unknown
timestamp: October 22, 2015, 04:37:11 pm
content: If I want to be able to replace precision resistors easily on a PCB (0.1 % tolerance / 5 ppm tempco), what is the best socket to use? I want it to not add significantly to the value of the resistors (or introduce noise), because these will be very high precision resistors with very low tempcos. There will be very little current flowing through the circuit <1ma. All resistors will be >=100 ohms and most >=1 kohm.It would also probably be a good idea if the sockets were made of the same metal/alloy as general resistor leads, so there is noise introduced at the junction (of the resistor with the socket). Also, SIP sockets have been suggested, but resistor leads tend to be very thin and I am not sure if a machined (circular hole) SIP socket would produce a tight enough fit.

author: Gyro
author_rank: Super Contributor
timestamp: October 22, 2015, 04:46:08 pm
content: You could maybe try the inserts from a turned-pin IC socket. The pins are a bit fragile but if you use a slightly larger pcb hole then they will fit down into the board. Not sure about thermocouple effects, but as long as they are both at the same temperature it should be ok. You ought to get a good firm contact anyway.

author: SharpEars
author_rank: Unknown
timestamp: October 22, 2015, 04:59:01 pm
content: Quote from: Gyro on October 22, 2015, 04:46:08 pmI saw a few people recommend machined SIP sockets, the problem is that resistor leads tend to be very thin compared to for example IC pins and I am not sure if a machined SIP would hold them.

author: SeanB
author_rank: Super Contributor
timestamp: October 22, 2015, 05:16:06 pm
content: If you are prepared to solder them in use turret pins, which allow you to just solder the resistors in place. If you are worried leave the leads untrimmed and only solder the ends, using some PTFE sleeving to cover the exposed lead. At least there the effects will be the same as if they were soldered in direct, and no noise at all.

author: Gyro
author_rank: Super Contributor
timestamp: October 22, 2015, 05:25:56 pm
content: QuoteThey're a good fit for standard 1/4W resistors (I use one in the head of my Zo probes for easy changing of the tip resistor). Precision resistors may possibly have smaller or larger diameter leads though.

author: SharpEars
author_rank: Unknown
timestamp: October 22, 2015, 06:30:14 pm
content: Quote from: Gyro on October 22, 2015, 05:25:56 pmI am using 1/8 W Vishay precision resistors which probably have thinner leads.

author: ajb
author_rank: Super Contributor
timestamp: October 23, 2015, 12:19:55 am
content: Mill Max has a whole range of machined contacts designed for a variety of lead diameters. I'd be surprised if they didn't have something that would suit your needs.

author: Smokey
author_rank: Super Contributor
timestamp: October 23, 2015, 12:39:50 am
content: Quote from: SeanB on October 22, 2015, 05:16:06 pmThis. Precision and sockets don't mix.

author: SharpEars
author_rank: Unknown
timestamp: October 23, 2015, 12:42:03 am
content: Quote from: Smokey on October 23, 2015, 12:39:50 amPrecision (resistors) and soldering don't mix either, which is why I am asking. There are several threads on this topic alone right here on eevblog with experimental evidence to prove theory. The heat of even a couple of seconds introduces tens of PPMs of drift to the resistor's value. Some of it wears off after several months, some is permanent.If you characterize resistors (e.g., for matching, tolerance, drift and/or tempco), soldering them can destroy that characterization. Hence there is a real need for sockets (which I'll admit come with their own issues that need to be considered).

author: Vgkid
author_rank: Super Contributor
timestamp: October 23, 2015, 01:30:13 am
content: What about the sockets for transistors(Do they even make those???) they have rather thin leads.HERE YOU GO... tranny/opamp sockets should work.http://www.mouser.com/Connectors/IC-Component-Sockets/_/N-211lkZscv7?P=1z0z2tkZ1z0yzpeZ1yzvwlbZ1z0x9arZ1z0x9blZ1z0wxmoZ1z0wx52

author: matseng
author_rank: Frequent Contributor
timestamp: October 23, 2015, 03:29:55 am
content: What about binding posts (aka banana jacks)? There are versions with a slot going down the threaded tube that the plug normally goes into i instead of the normal small hole.The binding posts can be soldered directly into a suitable sized hole in the pcb, and if having the slotted version then the resistor could just be dropped down into the slots and then the thumbscrews can be screwed into place.

author: LukeW
author_rank: Frequent Contributor
timestamp: October 23, 2015, 08:45:37 am
content: Leave plenty of lead length between the resistor body and the soldered turret - put the very end of the resistor lead on the turret. Along with practiced and careful soldering, this should avoid thermal damage during soldering.

author: Fungus
author_rank: Super Contributor
timestamp: October 23, 2015, 08:52:33 am
content: Quote from: SharpEars on October 23, 2015, 12:42:03 amYou can get special heatsinks for soldering stuff like that...

author: fivefish
author_rank: Frequent Contributor
timestamp: October 23, 2015, 09:18:04 am
content: Check out millmax sockets. They have sockets for a wide range of inside diameters.

author: savril
author_rank: Regular Contributor
timestamp: October 23, 2015, 02:21:50 pm
content: Why not wirewrap them ?

author: SharpEars
author_rank: Unknown
timestamp: October 23, 2015, 02:39:45 pm
content: Quote from: Fungus on October 23, 2015, 08:52:33 amHey, where do I get one of these - that's a great idea!

author: SharpEars
author_rank: Unknown
timestamp: October 23, 2015, 02:49:20 pm
content: OK, I can hold the lead with the flat part of these (to the left of and right before the cutters in the picture at the following link):I can also apply quite a bit of pressure and contact area with the lead, since these are after all pliers and have some serious mass at the contact area! Maybe I can put them in the freezer to get them to be really cold before soldering, allowing for even more soldering time and less chance of the heat making its way to the precision resistor body. Am I nuts or did I just come up with the best way of keeping the heat away from the component being soldered?

author: macboy
author_rank: Super Contributor
timestamp: October 23, 2015, 02:57:10 pm
content: Quote from: Fungus on October 23, 2015, 08:52:33 am+1 to soldering with a heatsink clip on the leads.The copper clip pictured above would work great. I have a couple of aluminum ones like this:Holding with pliers will have some effect but not as much. Steel just doesn't conduct heat nearly as well as either copper or aluminum. You are also much more likely to cause undue mechanical stress to the precision component that way. Stressing the lead close the the resistor body can also affect its value.Google "soldering heatsink clip". the picture above is directly from the Jameco website, but you can get them anywhere (mine came from Radio Shack).

author: SharpEars
author_rank: Unknown
timestamp: October 23, 2015, 03:09:01 pm
content: Quote from: macboy on October 23, 2015, 02:57:10 pmBut, the sheer mass of steel, much more contact area (2 cm of lead!) and better contact due to more pressure, combined with the fact that the pliers can be <=0 degrees C (straight out of a freezer) for as long as a minute, more than make up for the fact that they are made out of steel.I would not hold the leads too close to the part to avoid any sort of stress.