|
|
Hi Marv,
Yes, a number of "daring" hobbyists have been using SMD components - actually its getting so that all the new and exciting chips are coming out only in SMD format - very little through hole (for new stuff). I have long avoided using SMD because I can bearly see the components under a magnifying glass. Most of the ones I am using are a size know as 0805 (8 thousandths long, 5 thousandths wide) about the size of a number 2 pencil lead and there are at least two sizes smaller !!!! But, when they stop making a component you use in through -hole what is one to do?
Regarding the SMD dance - its a jitter bug tune I believe {:>). I understand that the surface tension of the liquid solder also pulls the components into perfect alignment on the pads if the board is jiggled lightly just before the solder solidifies.
There appear to be about 3 different paths hobbyist take to using SMD.
Many folks simply use a syringe filled with the solder paste and deposit the appropriate amount on each pin pad. And a number still attached the components using a fine tipped soldering iron.
Some go a bit further by using a syringe method but then popping the populated board into a toaster oven to solder it.
Then if you go a bit further, you use a stencil to deposit all the solder in one quick pass, place the components (which would now take the most time) and pop it in an oven.
I am told that the key is the laying down of the correct amount of solder through the stencil holes. Its especially critical for fine pitch components - because if you put too much paste down on the narrow closely spaced leads the solder can "slump" (technical term used by the SMD experts) and fall over onto the next lead.
So that is why I decided to see if I couldn't come up with a device that would lay down consistent amounts of solder through a stencil. Once I find the magic pressure required, then it should be easy to replicate the results from one run to the next - we will see {:>)
Ed
----- Original Message ----- From: "Marvin Kaye" <marv@lancaironline.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Friday, February 16, 2007 12:14 PM
Subject: [FlyRotary] Re: Rusty's Rv-8 For Sale!
Ed,
Your method has been proven and it certainly works. Jim Frantz, the guy who invented the PSS AOA instrument, used to do exactly what you're doing for repairs and modifications to boards as well as product development on a routine basis. While I've never witnessed it myself, I undersand the teeny SM chips do a little "dance" just as the flux/solder goes liquid and allows the components to settle down onto their pads. The effect can be witnessed through the glass of the oven door, provided it hasn't been previously clouded with the outgassing of a wayward calzone. And no, I don't know what tune the little buggers dance to, but suspect it's probably something very techno <g>.
<Marv>
"Tracy Crook" <lors01@msn.com> wrote:
Hi Ed,
I'll be very interested in that soldering experiment. Just the kind of 'real
world solution' I have come to expect of you ! :-) I farm that job out to PC
board contractors and it is one of the biggest expenses in building my stuff.
Tracy (Back from brother's divorce court hell)
----- Original Message -----
From: Ed Anderson<mailto:eanderson@carolina.rr.com>
To: Rotary motors in aircraft<mailto:flyrotary@lancaironline.net>
Sent: Thursday, February 15, 2007 8:16 PM
Subject: [FlyRotary] Re: Rusty's Rv-8 For Sale!
Actually, Rusty, given the rather limited engine knowledge of many (but not
all) of those on that list, they would have probably thought you meant a
radial engine {:>)
Well, the quick responses may mean you priced it realistically (or too low
{:>)).
I well understand your tendency to build. I just designed, machined and
assembled a gadget that will enable me to "print" solder paste to a PC board,
populate it with components and pop it in the oven. Went out and got an
inexpensive convection toaster oven that has an almost identical heat build up
profile to match that of the solder paste I'm using. No food in my "reflow"
oven!
I have the stencil placed over the PC board and the components all sorted
into individual small plastic boxes (used for holding beads that those engaged
with making beaded things use). Boy if I ever dropped that box, it would hard
to find those little critters not to mention sorting them out again {:>).
So going to get a good night sleep = steady hands and have a go at it
tomorrow. If it works it will considerably reduce the amount of time and
labor involved soldering up a board. If it doesn't - I'll chalk it up to
"lesson learned".
Well, next time have Richard fire off a flare!!
Ed
----- Original Message -----
From: Russell Duffy<mailto:rusty@radrotary.com>
To: Rotary motors in aircraft<mailto:flyrotary@lancaironline.net>
Sent: Thursday, February 15, 2007 7:23 PM
Subject: [FlyRotary] Re: Rusty's Rv-8 For Sale!
Well, you've finally done it,Rusty. Saw your e mail on the RV list
offering up your RV-8. Now you can come back to the "Light side of the Force"
and get to work on your single lung rotary.{:>).
Hi Ed,
Don't think I didn't see you talking about exhaust valves on the list. I
almost replied to that post, asking who wanted to take advice like that from
someone flying a rotary :-)
There was some agony involved in actually listing the plane, but it's for
the best. Amazingly, there are already two very serious prospects, and it's
only been for sale for a couple hours. Even more amazingly, one is in TX, and
knows Bill and Jason. Finding the right buyer rarely happens this quickly, so
I'll just expect these to fall through. Still, hopefully the selling thing
won't last too long.
BTW, if anyone cares, the sale info is here-
http://www.radrotary.com<http://www.radrotary.com/>
As for single rotors, I am still waiting for the redrive from Autoflight.
It's coming along, but running a couple weeks behind original estimates.
Since they haven't asked for any money yet, I guess I can forgive them :-)
Cheers,
Rusty
PS- I circled Richard's general vicinity for about 5 minutes Sunday, but
never did quite figure out which clearing was his strip. On the way over
there, I did manage to record 184 kts TAS at 800 ft :-)
--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
|
|