Cutting leads in tight places
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I am progressing on my K2 project, I just finished the steps on page
57 that had me solder several components to the bottom side of the RF board. My problem is getting my cutters into some of the tight places on the top of the board. I thought the hard part was over when I finished soldering without causing heat damage to near by components but I am finding it nearly impossible to trim the leads now. I have the recommended angle cutting tool but I still can't get down to board level with them to cut them anywhere near flush. Any ideas. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Cutting leads in tight places
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Lee:
>I am progressing on my K2 project, I just finished the steps on page >57 that had me solder several components to the bottom side of the >RF board. My problem is getting my cutters into some of the tight >places on the top of the board. I thought the hard part was over when >I finished soldering without causing heat damage to near by >components but I am finding it nearly impossible to trim the leads >now. I have the recommended angle cutting tool but I still can't get >down to board level with them to cut them anywhere near flush. What I've had to do in a couple instances was to merely grab the exposed lead with a pair of needle-nosed pliers (actually a pair of hemostats) and then pull a little on the lead and rock it back ;n forth until it breaks AT the soldered joint. Then I go back and re-flow (re-heat) the solder around the lead to ensure that I still have a solid connection. So far, this has worked in all instances. Another method is to pre-cut the leads to length before you solder. 73, Tom N0SS _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: Cutting leads in tight places
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In reply to this post by Lee H-2
Here's a different approach. Don't sweat it.
If you can't get down there with a small pair of cutters, then the excess lead isn't going to produce any poke wounds in your hands as you handle the board. Get as close as you can and leave what you can't I recall some difficulty when I built my K2 but I don't recall actually having to leave more than about 1/16 inch sticking up. I did some pre-trimming but I doubt I was smart enough to know when to do it. I just followed the manual. Hmm, you're doing the bottom components. Yep, that is when I did the bulk of my pre-cut activities. Didn't the manual say to pre-trim the parts? - Keith KD1E - - K2 5411 - -----Original Message----- From: Lee H I am progressing on my K2 project, I just finished the steps on page 57 that had me solder several components to the bottom side of the RF board. My problem is getting my cutters into some of the tight places on the top of the board. I thought the hard part was over when I finished soldering without causing heat damage to near by components but I am finding it nearly impossible to trim the leads now. I have the recommended angle cutting tool but I still can't get down to board level with them to cut them anywhere near flush. Any ideas. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: Cutting leads in tight places
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In reply to this post by Lee H-2
Lee,
I do not pre-trim the leads (but that is an excellent way to avoid the problem), but in places where it is tight to get the cutters in, I bend the lead over and point the cutter tips straight down toward the board to clip the lead. It is not quite flush cut, but it is close to the solder pad. I think pre-trimming is a pain because the part usually falls out when the board is flipped over to solder it in. Resistors can be soldered on the same side as the component easily, but a capacitor is more difficult to solder on the same side as the component unless it is mounted a bit above the board (try that with an electrolytic <G>). 73, Don W3FPR > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]]On Behalf Of Lee H > Sent: Monday, October 23, 2006 5:11 AM > To: [hidden email] > Subject: [Elecraft] Cutting leads in tight places > > > I am progressing on my K2 project, I just finished the steps on page > 57 that had me solder several components to the bottom side of the > RF board. My problem is getting my cutters into some of the tight > places on the top of the board. I thought the hard part was over when > I finished soldering without causing heat damage to near by > components but I am finding it nearly impossible to trim the leads > now. I have the recommended angle cutting tool but I still can't get > down to board level with them to cut them anywhere near flush. > > Any ideas. > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.408 / Virus Database: 268.13.9/490 - Release Date: 10/20/2006 > > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Lee H-2
The following is from a NASA-certified solderer ... me. (:-))
Contrary to the belief/practice of many, component leads protruding through a solder pad should NEVER be cut off flush with the board. They should be cut off at a length that is several diameters of the wire ... at least ... above the board. Yes, there are instances of machine-finished boards where the entire lead side of the board is ground or sanded off, but this is a process usually found in the mass-produced consumer product industry. "Wiggling" a lead to break(!) it off isn't the way to do it. The component's leads should be pre-cut to the desired length before insertion into the holes for soldering. FWIW ... 73! Ken Kopp - K0PP [hidden email] or [hidden email] _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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-----Original Message----- From: Ken Kopp The following is from a NASA-certified solderer ... me. (:-)) Contrary to the belief/practice of many, component leads protruding through a solder pad should NEVER be cut off flush with the board. They should be cut off at a length that is several diameters of the wire ... at least ... above the board. ------------------------ Above the board or above the top of the solder joint? Why leave wire protruding? - Keith KD1E - _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Ken Kopp-2
At 09:30 AM 10/23/2006, Ken Kopp wrote...
>The following is from a NASA-certified solderer ... me. (:-)) > >Contrary to the belief/practice of many, component leads protruding through a solder pad should NEVER be cut off flush with the board. They should be cut off at a length that is several diameters of the wire ... at least ... above the board. Time for a refresher class. According to the current standard, NASA-STD-8739.3 w/Change 2, December 1997, Section 8.5(.3) ( http://www.hq.nasa.gov/office/codeq/sldrbch2.pdf ): "Straight-Through Lead Terminations. Part leads terminated straight through the PWB shall extend a minimum of 0.5mm (0.020 inch) and a maximum of 2.29mm (0.090 inch)" .020" is one lead diameter for a 1/8W resistor, and can be less than one diameter for larger parts. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Darwin, Keith
The NASA wonks are correct in their citation of construction practices.
However, as hams we like to know "why" as well as "thou shalt not": In this case the bad thing being avoided is called "cold-working". The solder used to solder parts is an alloy of two of more metals, which arrange themselves in a lattice of greatest strength immediately before solidification of the joint. Any deformation of that joint after solidification (including that caused by thermal expansion and contraction) is called cold-working, and embrittles the joint to some degree, setting it up for future failure in a way which is nearly undetectable by our feeble eyes. This is why you shouldn't use toenail clippers, etc. to get at the last nub of an exposed lead -- by doing so you are cold-working the joint. Clip it instead at the top of the meniscus formed by the solder on the lead. FWIW, SMD parts are designed to thermally expand at roughly the same rate as PCB material in order to minimize this phenomenon, or else they are constructed so as to relieve thermal stress. Darwin, Keith wrote: > > Above the board or above the top of the solder joint? > > Why leave wire protruding? > > - Keith KD1E - > -- Marshall Jose, WA3VPZ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Lee H-2
Old fingernail clippers sometimes work.
Geoff, K6TFZ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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