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  • Author Author: jw0752
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I Need an Extra Finger

jw0752

Since I retired a couple years ago I have returned to my life long interest in electronics. What I have discovered is that I had not kept up with the technology. The manageable, through the hole, components that I was familiar with in the past have been replaced by something that is very small and solders directly to the surface of the board. Not wanting to miss out on playing with some of these really neat goodies I decided to begin to acquaint myself with the components and the new techniques I would need to learn. While I have been soldering for 55+ years I have seldom had to deal with the soldering of leads so closely spaced. To assist in trying the surface mounted chips I bought some Capital Advanced adapter boards from Newark Electronics and proceeded to attempt to solder the chips to them. The most difficult part was keeping the chip in place while I soldered the first leg. I was explaining to my very supportive wife how difficult it was not to disturb the position of the chip while soldering and in her usual intuitive way she volunteered to hold the chip with her finger while I soldered it. ( At this point she had not seen the size of the chip in question ,1.5mm x 2.5mm) While it was not practical for her to hold it, as usual she was right, what I needed was an extra finger.

 

I got together the following materials:

 

30 cm of bare 12 gauge copper wire

4 screws

piece of spring

6 cm of 3 mm brass tubing

 

20 minutes later after bending and soldering the pieces together I had cobbled together THE FINGER

 

image

 

I got one of the Capital Advance boards out and an LM 3410 LED driver that I wanted to try out.

 

image

 

I placed the IC on the board under THE FINGER. Once it was held down by the finger I made the minor adjustments needed to position it properly.

 

image

 

Now all that was left was the still challenging job of soldering the legs of the LM 3410 to the board.

 

Final product:

 

image

 

Now all that was left was to plug the LM 3410 LED Driver into a breadboard and wire up the circuit to see if it really would drive 5 series LEDs off of a 3.3 volt supply as advertised.

 

Not much to look at but it works as advertised.

 

image

 

Good Night Guys 1:10 AM

 

 

  • in reply to michaelwylie

    I have a range of tips, all metal.

    I don't so much mind the cost of the actual stencil (often way less than the cost of boards because mostly my prototypes are 4 layers or more and needed in  a hurry) but I haven't been able to justify the cost of  a proper screening frame. I've tried using stencils with lash ups of tape and old bits of board etc but find that they bow unless held tight. If you buy stencils with a rigid metal frame of course they aren't cheap any more.

    I'll buy a proper screening frame in the end I expect.

     

    MK

  • in reply to jw0752

    Hi John,

     

    You will find a new way to view the universe.

    Did I mention that I also explain how permanent magnets work and still obey Maxwell's equations?

     

    I have cause a minor stir on Linked In.  Some of the dyed in the wool QM physicists just do not want to believe that they are flogging a dead horse.

     

    DAB

  • in reply to michaelkellett

    It can be difficult to apply. I find a fine tip device like a dentist pick works well for getting just a tiny amount on the pad but the syringe with a fine tip works down to the 402 level. Does your syringe have a plastic tip or a metal one?

     

    I love stencils, but since I'm doing prototyping the added cost isn't justified.

  • in reply to DAB

    Thanks DAB - By the way I have on my to do list getting a copy of your book. It sounds very interesting.

    John

  • in reply to michaelwylie

    I find paste is much more difficult to apply than wire solder - so for 0402 - 1206 parts I melt a little solder on to one pad, solder the part on by reflowing the solder while placing the part with tweezers and then solder the other pad.

    For those horrible QFNs (with no or almost no visible legs) and some other packages I use solder paste, put on either with a syringe/compressed air dispenser or very rarely with a solder paste stencil. Then I reflow the solder using either  a hotplate, the el-cheapo Farnell under board hot air blaster or even the temperature controlled IR BGA re-working machine.

    For TQFP and the like I hold it in place by tacking  a couple of corner pins and then apply a lot of very runny liquid flux and run a bead of solder along the pins with an iron. Can easily do 0.5mm pitch pins like this.

     

    MK