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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