When i was using another PCB design tool, i built my own smd footprints . To do a quick prototype, i am using the linux "pcb" tool and the build-in footprints. The build-in footprints have pads with the same size as pins. When i build my own, i found it helpful to extend the pads beyond the pins. With enough flux, just let the solder suck in from the extended area into the pins. Also, it's easier to clear solder bridges on the extended area, rather than on the pins. I am adding 10 mils to the pads beyond the pins. Actually, easier to solder with longer extensions. What do you guys use?
SMD footprints
Started by ●June 19, 2021
Reply by ●June 19, 20212021-06-19
On Saturday, June 19, 2021 at 12:09:45 PM UTC-4, Ed Lee wrote:> When i was using another PCB design tool, i built my own smd footprints . To do a quick prototype, i am using the linux "pcb" tool and the build-in footprints. The build-in footprints have pads with the same size as pins. > > When i build my own, i found it helpful to extend the pads beyond the pins. With enough flux, just let the solder suck in from the extended area into the pins. Also, it's easier to clear solder bridges on the extended area, rather than on the pins. > > I am adding 10 mils to the pads beyond the pins. Actually, easier to solder with longer extensions. > > What do you guys use?There are IPC guidelines that are generally pretty good. One for reflow that has minimal expansion beyond the pins, but enough and another I think is for wave soldering (yes, you can wave solder surface mount) with larger extensions. The 10 mil might be good at the toe where most provide a significant extension. The sides often are only a couple of mils if that and the heel can be as little as 5 mil, but don't hold me to any of these numbers. It's been a while since I laid out a footprint. What is the "Linux pcb" tool? I didn't know anything came with the Linux distribution and there are a number that are available for Linux and are even primarily built for Linux with Windows support being an afterthought. KiCAD is a popular one. -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
Reply by ●June 19, 20212021-06-19
On Saturday, June 19, 2021 at 9:29:38 AM UTC-7, gnuarm.del...@gmail.com wrote:> On Saturday, June 19, 2021 at 12:09:45 PM UTC-4, Ed Lee wrote: > > When i was using another PCB design tool, i built my own smd footprints . To do a quick prototype, i am using the linux "pcb" tool and the build-in footprints. The build-in footprints have pads with the same size as pins. > > > > When i build my own, i found it helpful to extend the pads beyond the pins. With enough flux, just let the solder suck in from the extended area into the pins. Also, it's easier to clear solder bridges on the extended area, rather than on the pins. > > > > I am adding 10 mils to the pads beyond the pins. Actually, easier to solder with longer extensions. > > > > What do you guys use? > There are IPC guidelines that are generally pretty good. One for reflow that has minimal expansion beyond the pins, but enough and another I think is for wave soldering (yes, you can wave solder surface mount) with larger extensions. The 10 mil might be good at the toe where most provide a significant extension. The sides often are only a couple of mils if that and the heel can be as little as 5 mil, but don't hold me to any of these numbers. It's been a while since I laid out a footprint.Standard footprints work well with stencil and commercial builds. Extended pads work much easier for hand soldering and prototyping. But it takes up more space.> What is the "Linux pcb" tool? I didn't know anything came with the Linux distribution and there are a number that are available for Linux and are even primarily built for Linux with Windows support being an afterthought. KiCAD is a popular one.apt get install pcb (and gerbv) pcb allows auto generation of footprints and traces. I have hundreds of traces auto-gen using it. I use "sed s/350.08mil/360mil" to extend the footprint and verify it with "grep 350.08mil | wc == 100". 350.08mil is the outer position of the tqfp100 pads. Fortunately, there are exactly 100 occurrences of 350.08mil.
Reply by ●June 19, 20212021-06-19
søndag den 20. juni 2021 kl. 02.00.55 UTC+2 skrev Jasen Betts:> On 2021-06-19, Rick C <gnuarm.del...@gmail.com> wrote: > > On Saturday, June 19, 2021 at 12:09:45 PM UTC-4, Ed Lee wrote: > >> When i was using another PCB design tool, i built my own smd footprints . To do a quick prototype, i am using the linux "pcb" tool and the build-in footprints. The build-in footprints have pads with the same size as pins. > >> > >> When i build my own, i found it helpful to extend the pads beyond the pins. With enough flux, just let the solder suck in from the extended area into the pins. Also, it's easier to clear solder bridges on the extended area, rather than on the pins. > >> > >> I am adding 10 mils to the pads beyond the pins. Actually, easier to solder with longer extensions. > >> > >> What do you guys use? > > > > There are IPC guidelines that are generally pretty good. One for reflow that has minimal expansion beyond the pins, but enough and another I think is for wave soldering (yes, you can wave solder surface mount) with larger extensions. The 10 mil might be good at the toe where most provide a significant extension. The sides often are only a couple of mils if that and the heel can be as little as 5 mil, but don't hold me to any of these numbers. It's been a while since I laid out a footprint. > > > > What is the "Linux pcb" tool? I didn't know anything came with the Linux distribution and there are a number that are available for Linux and are even primarily built for Linux with Windows support being an afterthought. KiCAD is a popular one. > It's a tool called "PCB" that runs on linux. part of the gEDA/gaF suite. > I think the same D. J. Delorie who posts here occasionally is/was > somehow involved in its development. http://www.delorie.com/pcb/ > > With CERN's recent investment in KiCAD, and the resulting improvements, > interest in gEDA and "PCB" has waned.yeh, afaict it hasn't had any developement since 2013 or there abouts
Reply by ●June 19, 20212021-06-19
On Saturday, June 19, 2021 at 6:17:08 PM UTC-7, lang...@fonz.dk wrote:> søndag den 20. juni 2021 kl. 02.00.55 UTC+2 skrev Jasen Betts: > > On 2021-06-19, Rick C <gnuarm.del...@gmail.com> wrote: > > > On Saturday, June 19, 2021 at 12:09:45 PM UTC-4, Ed Lee wrote: > > >> When i was using another PCB design tool, i built my own smd footprints . To do a quick prototype, i am using the linux "pcb" tool and the build-in footprints. The build-in footprints have pads with the same size as pins. > > >> > > >> When i build my own, i found it helpful to extend the pads beyond the pins. With enough flux, just let the solder suck in from the extended area into the pins. Also, it's easier to clear solder bridges on the extended area, rather than on the pins. > > >> > > >> I am adding 10 mils to the pads beyond the pins. Actually, easier to solder with longer extensions. > > >> > > >> What do you guys use? > > > > > > There are IPC guidelines that are generally pretty good. One for reflow that has minimal expansion beyond the pins, but enough and another I think is for wave soldering (yes, you can wave solder surface mount) with larger extensions. The 10 mil might be good at the toe where most provide a significant extension. The sides often are only a couple of mils if that and the heel can be as little as 5 mil, but don't hold me to any of these numbers. It's been a while since I laid out a footprint. > > > > > > What is the "Linux pcb" tool? I didn't know anything came with the Linux distribution and there are a number that are available for Linux and are even primarily built for Linux with Windows support being an afterthought. KiCAD is a popular one. > > It's a tool called "PCB" that runs on linux. part of the gEDA/gaF suite. > > I think the same D. J. Delorie who posts here occasionally is/was > > somehow involved in its development. http://www.delorie.com/pcb/ > > > > With CERN's recent investment in KiCAD, and the resulting improvements, > > interest in gEDA and "PCB" has waned. > yeh, afaict it hasn't had any developement since 2013 or there aboutsIt's good enough for me. I don't really use much of the UI, just for preview after auto-gen. Mostly using it for generating gerber files.
Reply by ●June 20, 20212021-06-20
19.06.21 18:29, Rick C wrote:>On Saturday, June 19, 2021 at 12:09:45 PM UTC-4, Ed Lee wrote: >> When i was using another PCB design tool, i built my own smd footprints . To do a quick prototype, i am using the linux "pcb" tool and the build-in footprints. The build-in footprints have pads with the same size as pins. >> >> When i build my own, i found it helpful to extend the pads beyond the pins. With enough flux, just let the solder suck in from the extended area into the pins. Also, it's easier to clear solder bridges on the extended area, rather than on the pins. >> >> I am adding 10 mils to the pads beyond the pins. Actually, easier to solder with longer extensions. >> >> What do you guys use? > >There are IPC guidelines that are generally pretty good. One for reflow that has minimal expansion beyond the pins, but enough and another I think is for wave soldering (yes, you can wave solder surface mount) with larger extensions. The 10 mil might be good at the toe where most provide a significant extension. The sides often are only a couple of mils if that and the heel can be as little as 5 mil, but don't hold me to any of these numbers. It's been a while since I laid out a footprint. >On the topic of wave solder, you need to glue the parts first, that's the normal way I guess Is it possible to use solder paste, pick and place, flip the board and wave solder? -- Klaus
Reply by ●June 20, 20212021-06-20
On Sat, 19 Jun 2021 09:09:41 -0700 (PDT), Ed Lee <edward.ming.lee@gmail.com> wrote:>What do you guys use?Through-hole. A lot less bother.
Reply by ●June 20, 20212021-06-20
On 20/06/2021 09:19, Klaus Kragelund wrote:> Is it possible to use solder paste, pick and place, flip the board and > wave solder? > > -- > KlausI suppose in theory yes - if reflow tech uses high melting alloy and the wave solder alloy is a lower melting point alloy and temperature control sufficiently good. Never seen it done. Personally I have used mixed through hole and glue dot SMD wave solder technology with great success. Also two sided reflow with the lightweight parts held by surface tension and bigger ICs all on the topside. piglet
Reply by ●June 20, 20212021-06-20
On Sunday, June 20, 2021 at 4:19:25 AM UTC-4, Klaus Kragelund wrote:> 19.06.21 18:29, Rick C wrote: > >On Saturday, June 19, 2021 at 12:09:45 PM UTC-4, Ed Lee wrote: > >> When i was using another PCB design tool, i built my own smd footprints . To do a quick prototype, i am using the linux "pcb" tool and the build-in footprints. The build-in footprints have pads with the same size as pins. > >> > >> When i build my own, i found it helpful to extend the pads beyond the pins. With enough flux, just let the solder suck in from the extended area into the pins. Also, it's easier to clear solder bridges on the extended area, rather than on the pins. > >> > >> I am adding 10 mils to the pads beyond the pins. Actually, easier to solder with longer extensions. > >> > >> What do you guys use? > > > >There are IPC guidelines that are generally pretty good. One for reflow that has minimal expansion beyond the pins, but enough and another I think is for wave soldering (yes, you can wave solder surface mount) with larger extensions. The 10 mil might be good at the toe where most provide a significant extension. The sides often are only a couple of mils if that and the heel can be as little as 5 mil, but don't hold me to any of these numbers. It's been a while since I laid out a footprint. > > > On the topic of wave solder, you need to glue the parts first, that's the normal way I guess > > Is it possible to use solder paste, pick and place, flip the board and wave solder?Not sure what you are describing. If you mean using glue, yes. One outfit wanted to do that with my board. I never found out why, but someone finally said it was not necessary. -- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
Reply by ●June 20, 20212021-06-20
On Sunday, June 20, 2021 at 2:24:43 AM UTC-7, Cursitor Doom wrote:> On Sat, 19 Jun 2021 09:09:41 -0700 (PDT), Ed Lee > <edward....@gmail.com> wrote:> >What do you guys use? > Through-hole. A lot less bother.Yes, but i would need to do a lot of custom work. The pins are 20 mils apart horizontally. I need to bend them down and rotate 90 degree and laser drill less than 4 mils wide, perhaps oval holes. No, the part does not come in 100 pins DIP.