[time-nuts] low noise multiplication to 100 MHz

Herbert Poetzl herbert at 13thfloor.at
Wed Jan 27 04:52:57 EST 2016


On Tue, Jan 26, 2016 at 06:57:54AM +0000, Mark Sims wrote:
> Actually not hard to do... lay out circuit board (free version
> of Eagle), have boards fab'd at Oshpark.com or your favorite
> Chinese proto shop (I like gojgo.com). Have solder paste
> stencil made at oshstencils.com. Squeege solder paste down with
> a credit card. Place components by hand. Reflow board with a
> modified toaster oven, electric skillet, hot air tool, etc.

Because I build and solder SMD boards on a regular basis,
I would like to add a few hints and tricks here which can 
simplify the task significantly:

For one-sided designs, the skillet method is really simple
and if the temperature is right, gives excellent results.

There are a bunch of ceramic heater elements (PTC) on eBay
and they often provide the perfect temperature stability
without the need for actual regulation (i.e. connect them
to a current limited power supply and it will reach a 
specific temperature at a given current).

As they are small, they work perfectly under a microscope
and you can not only watch the solder reflow, you can also
move the parts around in the liquid solder.

Most SMD components can also be soldered by hand with a
soldering iron, which doesn't even have to have a delicate
tip because there is an easy way with the help of (usually
red) thixotropic glue.

You first place a little dot or line of glue where the SMD
component will go (obviously not on the pads but between :) 
and then you place the component (down to 0201 imperial) 
with tweezers or a vacuum pick-up tool (doesn't need to be
extremely precise at this point) and now you can move the 
part into its final position with the help of an acupuncture 
needle.

Once all the components have been placed (the glue stays
liquid for several hours, probably days) and oriented/aligned
perfectly, you heat up the entire board to 120-160°C for
about 10 minutes which polymerizes the glue and thus fixes 
the parts in place.

You can then apply a good amount of solder on all the tiny 
pads to make sure that they are well connected. Heating the
entire PCB to around 150-180°C will help a lot and usually
doesn't harm the board or components (iron temperature can
be as low as 280°C which reduces the danger of overheating
dramatically). Do not worry about accidential bridges and
excessive solder, this will be fixed in the next step.

Once the parts have been soldered in place, you get a solder
wick (I prefer to use one of those highly flexible silicone
wires with hundreds of tiny conductors - you need to strip
it down to the copper wires first) and some flux to remove 
excessive solder from the joints.

After that, clean up the board (i.e. remove flux and other
stuff) with a flux remover or alcohol (isopropanol).

Here a few examples what can be done without hot air gun or 
reflow oven:

http://vserver.13thfloor.at/Stuff/AXIOM/pmod_assembled_top_600dpi.png
http://vserver.13thfloor.at/Stuff/AXIOM/pmod_assembled_bottom_600dpi.png
http://vserver.13thfloor.at/Stuff/AXIOM/BETA/pmod_clock_nosma.png
https://wiki.apertus.org/images/4/42/Axiom_Beta_Plugin_Module_1x_HDMI_v0.4_BOT.jpg
https://wiki.apertus.org/images/c/c0/BetaSensorBoardZIF_0.18_2.jpg
https://wiki.apertus.org/images/d/da/BetaMainboard_0.32_BOTTOM.jpg
http://vserver.13thfloor.at/Stuff/AXIOM/BETA/axiom_beta_power_board_v0.18_r1.0_fix01.jpg
http://vserver.13thfloor.at/Stuff/AXIOM/BETA/axiom_beta_power_board_v0.18_r1.0_fix02.jpg

And some links to the mentioned helpers:

http://www.ebay.com/itm/PTC-heating-element-100W-AC-DC-12V-constant-temperature-60-21mm-/151727264825
www.ebay.com/itm/AC-DC-12V-40W-PTC-Heater-Element-Thermostat-Heating-Plate-for-Warmer-Hot-Melter-/252212420224
www.ebay.com/itm/1Pc-40g-30mL-SMD-SMT-PCB-BGA-IC-Stencil-Paste-Dispenser-Red-Glue-Effective-Work-/321845571034
http://uk.farnell.com/multi-contact/60-7180-21/litze-blank-hochflex-0-5qmm-tpe/dp/135276
http://www.ebay.com/itm/5pcs-BGA-SMD-Soldering-Paste-Flux-Grease-Volume-10cc-RMA-223-/281358896876
http://uk.farnell.com/pro-power/ppc120/propower-flussmittelentfernerspray/dp/1736213

If you have any problems or general questions, do not
hesitate to email me.

Best,
Herbert

> If you want to get anywhere in electronics these days, you
> really need to get set up to do simple SMD work. It's not hard
> or expensive. The days of point to point wiring of vacuum
> tubes to terminal strips be looong gone. Through-hole and DIP
> packages are not far behind.
> 
> -------
> > There are other neat parts out there but again who is able to 
> solder  them. 		 	   		  
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