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Re: [softrock40] Some SMT opinions

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  • Jorge Macias
    I bought in ebay http://cgi.ebay.com/1pcs-50g-MCN-300-Soldering-Solder-Paste-63-37-25-45um-/200598351069?pt=LH_DefaultDomain_0&hash=item2eb497ecdd and the
    Message 1 of 8 , Aug 1, 2011
      I bought in ebay
      and the thermometer

      On Sat, Jul 30, 2011 at 6:57 PM, Allen West <kb4ra@...> wrote:

      Where do you get solder paste and an IR thermometer?  When I google for paste I keep coming up with the gallon size.

      From: AI2Q <ai2q@...>
      To: softrock40@yahoogroups.com
      Sent: Friday, July 29, 2011 9:24 AM
      Subject: [softrock40] Some SMT opinions

      KB1GTT and myself have been making up dozens of very small PCBs using 1206- and 0603-sized SMT parts, and we have been using a homebrew reflow oven made from a Black and Decker infrared toaster oven. It's heating element is controlled with a 40A solid-state relay through a controller board connected to my PC with a USB connection. We use solder paste.
      The TechFX software we use runs under XP and gives you a way to set a variety of profiles (preheat, soak, reflow, cooldown). What's neat is that you can graphically watch the controller in action, thanks to its closed loop operation using a thermocouple detector inside the oven.
      While this set-up is FB for production runs, I would not recommend reflow for any one-off ham project such as a Softrock PCB. The reason? Well, if there should be an error, such as tombstoning (where a small SMT part stands up on edge), or movement of a fine-pitch SMD device, then the board must be reworked. Yes, you can rework just that part that needs attention, but sometimes a board can have multiple faults. Rework can be tough.
      I would recommend going at it the old fashioned way, namely one part at a time, testing as you go as per Robby's notes. Use ordinary solder and ChipQuik flux from a syringe.
      By the way, my daily transceiver is a G3XJP design PIC-a-STAR, using hundreds of SMT devices on many PCBs. It was all assembled by hand. ChipQuik is key to both successful soldering and rework. Fabulous stuff.
      Vy 73, AI2Q, Alex
      Member: ARRL, FOC, RSGB, CWops, QRP-L, Antique Wireless Association, Wide Area Amateur Radio Network, New England Radio Discussion Society (NERDS)
      ----- Original Message -----
      Sent: Thursday, July 28, 2011 1:21 PM
      Subject: Re: [softrock40] Do all SMT first on RXTX?

      I too have used the cup warmer/hot air approach on two Lite's and I working on another lite and a couple Ensemble RXs. I do the hot air by hand.

      One thing I ran into on the Ensemble RX is that the board was too big for my cup warmer. Luckily our stove is one of the glass tops, so I used an IR thermometer to set the temp of one of the 'burners' to the same as the cup warmer (about 230 degF). Worked just great.

      I use a syringe to apply the solder paste and the only problem I've had is that I am too stingy with the paste for the multi-pin devices, so I often have to go touch up a pin or two. I use a high power eye loupe to inspect all the connections before proceeding.


      On Thu, Jul 28, 2011 at 8:24 AM, MIKE DURKIN <Patriot121@...> wrote:
      when you do the hot air part ... do you do it by hand or do you use a stand ?

      Mike KC7NOA

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