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Date: | Sun, 15 Mar 2009 17:20:48 -0500 |
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John,
We don't have a selective solder machine where I work. But your email is
going into a folder where I save the ones that I think will be something
that will be very useful sometime in the future.
I read all of your emails with great interest because of the detail in all
of your responses.
Thank-you very much!
Steve
----- Original Message -----
From: "John Goulet" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, March 15, 2009 11:39 AM
Subject: Re: [TN] Selective Soldering design rules
Tell me which type system you got because the design requirement changes. I
know the requirements for Selective solder pallets for wave, selective
solder carriers for the Vitronic Soltec MySelective 6748 & 6749 which are
gantry based systems with a unique gripper assembly that picks up the edge
of the PCA or carrier from the conveyor. They have PCB gripper which if
designed properly will pick up carriers, otherwise if you buy the pallet
only gripper then you will always have to use pallets/carriers but you save
all the setup time since each carrier will have the same outline. I designed
some gripper holdowns but it may be easier but more expensive to have clamps
to keep SIP components and switches from tifting or tilting during solder if
you use the tilt features to clear the adjacent SMT parts. The carrier edge
would have a lip even with the top surface 5mm deep, 2 mm thick to simulate
a board.
The RPS, ACE and Seho Seletives moves the solder pot under the board so
parts tilting is less of an issue. Of course the speed at which the board
goes in and then stops could tilt some parts. The ACE Kiss 104 doesn't have
the issue since you load the boards directly into the rails at the edge
stop.
- The common considerations are:
1. Use a window frame type carrier to provide enough support that the board
stays flat.
2. Based on the thickness and tab versus scoured panels you need to access
if there should be some threaded inserts in a few places where 4-40 or 6-32
hex standoffs can be used to secure the board through the mounting holes or
inbetween the tabs of the panel to prevent bowed boards from lifting off the
carrier.
3. The open design provides the preheat or nitrogen blanket to preheat the
board. The other reason is to provide provide a 1/2" drag out clearance for
the nozzle. To reduce shorts you have to come off the last row of pins at a
45 degree angle. You don't want to hit the center support rail nor the edge
of the carrier with the nozzle. Unlike a wave pallet where all you need is
1-2 mm ( .055"0.100" clearance now you need to assure that 6mm - 12mm nozzle
can drag past the component without hitting the pallet.
4. When you make a two-up carrier look at the drag-off clearance and
determine if you need to rotatae one of the boards so you can drag in
towards the edge of the carrier. It way not be possible to drag toward the
narrow center strip since you can't cut away any of the center support. Also
thermally you may want to put the thermally massive parts closer together so
they are heating up rather than cooling off.
5. Soldering tips:
- The smaller the nozzle the hotter the solder pot temp since the solder
temp at the exit of the nozzle will be less.
- Tin/Lead drag off speed is speed is fast 2mm sec. Lead Free the drag off
speed is very slow to get the solder to snap off and not bridge, .5mm sec.
One more thing - The vendor must assure each carrier is exactly the same
from the board edge. I had programmed the first proto carrier then ordered
five more and although they looked the same I had to modify the other 5.
This was because initially I thought it was the repeatability of the machine
as I cycled through the carriers. Then I numbered them and found what the
issue was.
I hope this helps.
John Goulet Process Engineer
----- Original Message -----
From: "Jim Mosher" <[log in to unmask]>
To: [log in to unmask]
Sent: Monday, February 23, 2009 1:36:59 PM GMT -05:00 US/Canada Eastern
Subject: [TN] Selective Soldering design rules
We are in the process of installing "Selective Soldering" equipment for the
first
time. Does anyone have a generic "Design Rules Guideline" for this type of
equipment that they would be willing to share.
Jim Mosher
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