#linuxcnc-devel Logs

Feb 28 2019

10:02 AM JT-Shop: pcw_home: hows the 7i77's 76 etc coming along?
10:05 AM pcw_home: Yeah but we've overloaded our assy house again >2000 cards being assembled
10:05 AM pcw_home: unfortunately ran out of many cards at the same time
10:07 AM JT-Shop: ok just wondering
10:07 AM JT-Shop: what does the assy house do? just curious
10:08 AM pcw_home: solders the parts on
10:09 AM JT-Shop: ok, so one place makes the boards and another place assembles them?
10:09 AM pcw_home: Yes we get the PCBs from one source then send the PCBs and parts to the assy house. They first screen print the solder on the cards
10:10 AM JT-Shop: cool
10:10 AM pcw_home: then place the components in the solder paste and run the PCBs with solder+parts through a oven
10:12 AM pcw_home: 2000 boards *~100 parts/board so 200,000 parts placed
10:12 AM JT-Shop: wow
10:13 AM pcw_home: so takes a while with the rather small assy house we use
10:13 AM JT-Shop: I've seen a pick and place and reflow (I think you call it that) oven once
10:13 AM pcw_home: yes reflow is the word i forgot
10:14 AM pcw_home: Ive been doing protos with low temp solder paste and its _really_ nice
10:19 AM pcw_home: you can reflow with a hot air gun on the back of the PCB with no danger of overheating anything
10:19 AM pcw_home: ( low temp = 138 C MP ) not good for power (hot) electronics but fine otherwise
10:20 AM skunkworks: There is a guy on youtube that fixes macbooks.. He is amazing with a hot air gun...
10:22 AM pcw_home: Yeah, I think I've seen him (louis something?) I have a rework setup, but with low temp solder a crufty old Grainger hot air gun is fine
10:23 AM skunkworks: yes
10:26 AM skunkworks: I got a tour of ibm's factory in eau claire wi. (iirc) They were making motherboards there.. It may have been their prototyping factory - I don't remember. but at the time they were having problems with the high density through hole processor sockets bridging solder.
10:29 AM skunkworks: when the wave soldered them
10:32 AM pcw_home: Yeah solder bridging is an issue with wave soldering as you get denser
10:33 AM skunkworks: this was early 90's
10:34 AM pcw_home: Our assy house has a weird system for through hole soldering that does one joint at a time
10:34 AM skunkworks: like a robot solding iron?
10:35 AM pcw_home: tiny solder pot and robot
10:35 AM pcw_home: (and vision system)
10:36 AM pcw_home: less thermal stress, works with double sided SMT etc (but slow of course)