Resistor and capacitor installation techniques: trim before or after soldering?
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Resistor and capacitor installation techniques: trim before or after soldering?
 
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Tony,
Thanks for the very detailed explanation. I know we are stressing the moderators with these somewhat OT postings, but I have learned something today. Your note about lead in solder is very apropos. I know that NASA is not wanting to have solder "whiskers" in any of their critical space equipment: https://nepp.nasa.gov/Whisker/background/index.htm I usually hunt down tin/lead solder at Hamfests. When I'm asked why I'm risking lead exposure when soldering, I quote a line from one of our former Presidents: "I don't inhale"! Thanks for the great discussion! '73 de JIM N2ZZ -----Original Message----- From: N2TK, Tony [mailto:[hidden email]] Sent: Sunday, March 25, 2018 12:58 PM To: 'Doug Renwick'; 'James F. Boehner MD'; 'JEROME SODUS'; [hidden email] Subject: RE: [Elecraft] Resistor and capacitor installation techniques: trim before or after soldering? Hi Jim, Doug is correct about military and space work. All parts are precut or have spacers installed prior to board mounting. Between flux, solder/flux and mechanical means the parts are held in place until the reflow oven. For some programs, boards are not allowed to be reworked. Some programs allow rework. There is a very detailed procedure for reworking a board - MIL-PRF-38535 and MIL-STD-883. But, our applications and most commercial applications do not see the stress, temperature range or vibration that some of these mil and space boards see. So, for most of us bending the leads to hold the part, solder and cut is fine. You can re-solder after cutting to be sure. Years ago at a NASA meeting, they were told you do not need a tool meeting MIL-STD and MIL-PRF to make a board that meets those specs. So, have the right solder and right temp on the soldering tool and the right tip and make a nice flowing shiny solder connection. By the way, military space solder is not RoHS compliant. There will be lead in the solder. 73, N2TK, Tony -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Doug Renwick Sent: Sunday, March 25, 2018 12:05 PM To: 'James F. Boehner MD' <[hidden email]>; 'JEROME SODUS' <[hidden email]>; [hidden email] Subject: Re: [Elecraft] Resistor and capacitor installation techniques: trim before or after soldering? Heathkit recommended the "bad practice" saying "solder the leads to the foil and cut off the excess lead lengths". Reprimanding a technician for doing this is insane. Doug "Political correctness is a weapon used to silence people who tell the truth" - Ayaan Hirsi Ali -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of James F. Boehner MD via Elecraft Sent: March-25-18 9:33 AM To: 'JEROME SODUS'; [hidden email] Subject: [Elecraft] Resistor and capacitor installation techniques: trimbefore or after soldering? Jerome, Now this is interesting. This is totally opposite of the way most of us were taught to solder. Among the kits I used to put together were Heathkit and Ramsey, both of whom recommended securing the parts in place by spreading the leads, soldering, and then cutting the wires close to the solder blob, checking for shorts. I assume that goes for Elecraft also, but I have not built any of their radios as kits, so not sure. So how did NASA handle the potential difficulties? Did they have precut parts? Did the tech have to place the part in the board and cut the leads first? If the part was loose, how was it held close to the board, owing to the fact that holding the solder and the iron took two hands? What if the lead length was overestimated and potentially could cause a short? Could the wire be cut and the joint reheated, or did the part have to be removed, recut and reinserted? Just trying to picture the operation. '73 de JIM N2ZZ -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of JEROME SODUS Sent: Saturday, March 24, 2018 11:40 PM To: [hidden email] Subject: Re: [Elecraft] Resistor and capacitor installation techniques: trim before or after soldering? About Message#15 copied below.... Sorry but cutting wires after soldering is "bad practice"; NASA wanted the soldered connection left undisturbed. If I ever saw an assembler or tech doing that "bad practice", they'd get a verbal warning that first time and a written warning if it ever happened again; but I had good, conscientious people and never had to do that. So, tin the wires if needed; position the part and then trim wires before doing the final soldering. 73 Jerry KM3K Message: 15 Date: Sat, 24 Mar 2018 19:39:47 +0000 From: Bill Johnson <[hidden email]> To: "[hidden email]" <[hidden email]>, 'Mark Petrovic' <[hidden email]>, "[hidden email]" <[hidden email]> Subject: Re: [Elecraft] Resistor and capacitor installation techniques: trim before or after soldering? Message-ID: <[hidden email] OM> Content-Type: text/plain; charset="us-ascii" Follow the instructions and solder as directed. There are components on both sides as I recall with the majority on the top. The leads need be spread to hold the components in place on the board. Once done soldering use a flush cut wirecutter to remove the excess. Not a good idea to trim them before soldering. 72 & 73, Bill K9YEQ FT'er for K2, KX1, KX3, KXPA100, KAT500, W2, etc. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Jim,
There is actually a way to have your cake and eat it too. Supply the surface mount parts or parts with leads with gold solder pads or leads. Most space parts come this way anyways. These meet RoHS. Prior to mounting on the boards use hot solder pot with SnPb solder to displace the gold (usually a two pot process). But this causes its own set of problems. Many space parts suppliers now offer a hot solder dip service with SnPb (Tin/Lead) solder. Usually the only place RoHS is mentioned is with Europe. But the space community gets a dispensation in regards to using lead solder (SnPb). No one wants to take a chance with whiskers in space. And it is amazing how fast they can grow without an atmosphere. SnPb also now applies to most things that fly real high, not just satellites. It is common practice to use a clear conformal coating over the board. That slows down the whisker process somewhat, especially if you play with topology. Try repairing that board. Most satellites are designed for a 15 year lifetime. So whiskers are a big issue. There are exceptions to that with some of the latest commercial constellations. Microsats (10cm cube (1U) to several "U's") have a very short lifetime (hours to a couple months) usually don't worry about whiskers or radiation issues, so far. It is amazing how long a pound of good SnPb solder will last. It is a good investment. Sorry for all the bandwidth and straying. N2TK, Tony -----Original Message----- From: James F. Boehner MD [mailto:[hidden email]] Sent: Sunday, March 25, 2018 2:10 PM To: 'N2TK, Tony' <[hidden email]>; 'Doug Renwick' <[hidden email]>; 'JEROME SODUS' <[hidden email]>; [hidden email] Subject: Resistor and capacitor installation techniques: trim before or after soldering? Tony, Thanks for the very detailed explanation. I know we are stressing the moderators with these somewhat OT postings, but I have learned something today. Your note about lead in solder is very apropos. I know that NASA is not wanting to have solder "whiskers" in any of their critical space equipment: https://nepp.nasa.gov/Whisker/background/index.htm I usually hunt down tin/lead solder at Hamfests. When I'm asked why I'm risking lead exposure when soldering, I quote a line from one of our former Presidents: "I don't inhale"! Thanks for the great discussion! '73 de JIM N2ZZ -----Original Message----- From: N2TK, Tony [mailto:[hidden email]] Sent: Sunday, March 25, 2018 12:58 PM To: 'Doug Renwick'; 'James F. Boehner MD'; 'JEROME SODUS'; [hidden email] Subject: RE: [Elecraft] Resistor and capacitor installation techniques: trim before or after soldering? Hi Jim, Doug is correct about military and space work. All parts are precut or have spacers installed prior to board mounting. Between flux, solder/flux and mechanical means the parts are held in place until the reflow oven. For some programs, boards are not allowed to be reworked. Some programs allow rework. There is a very detailed procedure for reworking a board - MIL-PRF-38535 and MIL-STD-883. But, our applications and most commercial applications do not see the stress, temperature range or vibration that some of these mil and space boards see. So, for most of us bending the leads to hold the part, solder and cut is fine. You can re-solder after cutting to be sure. Years ago at a NASA meeting, they were told you do not need a tool meeting MIL-STD and MIL-PRF to make a board that meets those specs. So, have the right solder and right temp on the soldering tool and the right tip and make a nice flowing shiny solder connection. By the way, military space solder is not RoHS compliant. There will be lead in the solder. 73, N2TK, Tony -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Doug Renwick Sent: Sunday, March 25, 2018 12:05 PM To: 'James F. Boehner MD' <[hidden email]>; 'JEROME SODUS' <[hidden email]>; [hidden email] Subject: Re: [Elecraft] Resistor and capacitor installation techniques: trim before or after soldering? Heathkit recommended the "bad practice" saying "solder the leads to the foil and cut off the excess lead lengths". Reprimanding a technician for doing this is insane. Doug "Political correctness is a weapon used to silence people who tell the truth" - Ayaan Hirsi Ali -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of James F. Boehner MD via Elecraft Sent: March-25-18 9:33 AM To: 'JEROME SODUS'; [hidden email] Subject: [Elecraft] Resistor and capacitor installation techniques: trimbefore or after soldering? Jerome, Now this is interesting. This is totally opposite of the way most of us were taught to solder. Among the kits I used to put together were Heathkit and Ramsey, both of whom recommended securing the parts in place by spreading the leads, soldering, and then cutting the wires close to the solder blob, checking for shorts. I assume that goes for Elecraft also, but I have not built any of their radios as kits, so not sure. So how did NASA handle the potential difficulties? Did they have precut parts? Did the tech have to place the part in the board and cut the leads first? If the part was loose, how was it held close to the board, owing to the fact that holding the solder and the iron took two hands? What if the lead length was overestimated and potentially could cause a short? Could the wire be cut and the joint reheated, or did the part have to be removed, recut and reinserted? Just trying to picture the operation. '73 de JIM N2ZZ -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of JEROME SODUS Sent: Saturday, March 24, 2018 11:40 PM To: [hidden email] Subject: Re: [Elecraft] Resistor and capacitor installation techniques: trim before or after soldering? About Message#15 copied below.... Sorry but cutting wires after soldering is "bad practice"; NASA wanted the soldered connection left undisturbed. If I ever saw an assembler or tech doing that "bad practice", they'd get a verbal warning that first time and a written warning if it ever happened again; but I had good, conscientious people and never had to do that. So, tin the wires if needed; position the part and then trim wires before doing the final soldering. 73 Jerry KM3K Message: 15 Date: Sat, 24 Mar 2018 19:39:47 +0000 From: Bill Johnson <[hidden email]> To: "[hidden email]" <[hidden email]>, 'Mark Petrovic' <[hidden email]>, "[hidden email]" <[hidden email]> Subject: Re: [Elecraft] Resistor and capacitor installation techniques: trim before or after soldering? Message-ID: <[hidden email] OM> Content-Type: text/plain; charset="us-ascii" Follow the instructions and solder as directed. There are components on both sides as I recall with the majority on the top. The leads need be spread to hold the components in place on the board. Once done soldering use a flush cut wirecutter to remove the excess. Not a good idea to trim them before soldering. 72 & 73, Bill K9YEQ FT'er for K2, KX1, KX3, KXPA100, KAT500, W2, etc. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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