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Thanks, Bob.
It turns out a fairly light pressure is apparently required. Too much and the squeegee scopes paste out of the pad area and too little pressure and it leaves too much for the finer pitch components. I don't think board thickness is going to matter. What I intend to do if that happens is simply use a different thickness acrylic sheet to hold the board and stand-off the stencil.
I'll gain some experience with the other two PC boards. I find that my scheme for placing the components - all capacitors, all resistors, all diodes, etc. does not work well. Need a scheme that starts from the bottom and works up, top and works down or center and works out regardless of component type - otherwise your tweezers knocks previously place components out of place. Also you do need those tweezers that have a dip in the end so you can clear closely place components.
Old shaky hands can really shove a tiny component all over the place, wiping the paste off the pad, etc. So a good arm brace would help.
I decided its doable, but I think I will design the board to use only 1206 size and not the smaller 0805 I was trying to use. Will make life easier. In fact, I sat down in a hour or less and redid the board design- now I have to find all new components in the catalogs.
Ed
----- Original Message ----- From: "Bob White" <rlwhite@comcast.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, February 22, 2007 3:56 PM
Subject: [FlyRotary] Re: Cooked Board - Really!IV
That's really looking good Ed. I hope that pressure adjustment isn't
so critical that you have a hard time getting good repeatability. Will
slight variations in board thickness be a problem?
Bob W.
On Thu, 22 Feb 2007 15:40:18 -0500
"Ed Anderson" <eanderson@carolina.rr.com> wrote:
On the first solder run, I had too much pressure and while the area of the solder paste deposit was excellent (even on the 0.25mm socket lands), there was too little quantity of solder to hold the hold the components in position.
The second solder run I used less squeegee pressure and it left (did not scope it out) a large volume of solder (too much in the case of the 0.25mm socket lands and they bridged). Solder wick may be able to get the excess solder out.
I have two more boards to experiment with - hopefully by the end I will have it down.
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda/index.html
-- N93BD - Rotary Powered BD-4 - http://www.bob-white.com
First Flight: 11/23/2006 7:50AM - 3.3 Hours Total Time
Cables for your rotary installation - http://www.roblinphoto.com/shop/
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