Vitaliy wrote:
> We used to hand-assemble and hand-solder our PTH boards. Recently we started 
> hand-assembling SMT boards, and IMHO the latter is considerably easier, 
> especially if you're not dealing with the really tiny stuff. Although steady 
> hands and sharp eyes are a must. :)
>   
Hand-soldering PTH is painful...  We started out that way.   Then I went 
to the "dip the whole board in flux, preheat it on a old electric grill, 
and then dip it in a pot of molten solder" method.   That makes PTH much 
easier, except doing 100 boards/month that way also becomes so tedious 
after a few months that it's really hard to feel the desire to run a 
batch of boards.   This is primariliy because of how agressive the 
environment is - you know, flux fumes, hot solder, etc..  It is not 
pleasant at all.

The Wave Solder machine made this a whole heck of a lot easier.

What I like about the PTH process the way we do it today is that my 
hand-inserter is able to do the insertion at their leisure onto some 
foam-sided 1/4" boards.  Or more specifically, we have cut/trim machines 
which precut all of the components to the appropriate length.  Then at 
insertion time, we just lay the panels on a piece of insertion-grade 
conductive foam which we have glued to a piece of paneling as a backer, 
and the person doing the insertion is able to insert how ever many 
boards we expect to solder with no rush to get them actually in the wave 
solder machine.   Once every couple weeks we fire up the wave solder 
machine, and run a fair number of boards through it, and basically stack 
them for use over the next couple of weeks.  Those boards could have 
been inserted days or weeks previously.

In the SMD world, I dislike the "criticality" about the whole placement 
process.   That is, from the point you put the paste on the board, you 
only have a certain period of time to place all the components and get 
it into the oven.   Or put differently, if you hand-place your placer 
can't work on a different schedule than the person who is the oven 
person - who unfortunately is often not the same person just because 
good eyesight and fine motor control skills are not necessarily in the 
same person as someone who can tweak an oven and figure out what they 
need to change in the process to get good results. 

I am curious though...  How are you "pasting and placing" the SMD 
today?    I do have some low-volume products I am really thinking about 
doing this way just because SMD is the easiest way to do them.
> We never considered a paste dispenser. It seems to me that if the volume is 
> too low for a stencil, manual dispensing (syringe) works just fine, until 
> the volume ramps up to the point where a stencil becomes a viable option. I 
> guess it really depends on how complex the board is? What is the additional 
> cost of a paste dispenser (for break-even calculations)?
>   
The cost of a paste dispenser really depends on the unit.   Some are 
really cheap - a couple hundred dollars.  Others more so..   Really most 
dispensers are just that syringe you already use mounted to the head in 
such a way that the P&P can put the syringe in the right spot and 
dispense.  I'm assuming you're using a semi-automatic dispenser on the 
syringe....  if not, then modify the above statement accordingly.

What I really don't like about the whole stencil thing is the setup and 
cleanup costs.   Compare the two options, in my context.  That is, I 
usually run a 4-5 different panels, perhaps 3-4 "copies" of each panel.

Stencils: You have a set of stencils for each panel.  For each panel you 
have to mount the stencil including board alignment, "screen" 3-4 
boards, clean up that stencil, put the next one on, and so on.   You're 
putting down 4-5 stencils and cleaning 4-5 stencils and it's a real 
pain.  Plus you're placing, which is included in the other option.

P&P w/dispenser:  You have a P&P machine with a dispenser.  The P&P 
machine has all of your common parts on it already.  The dispenser needs 
to be set up once at the start of the entire run (and perhaps be 
refilled occasionally), but to run 4-5 different panels, it's just put 
the board in the P&P, select the right board file and hit go.

I would expect that one person could keep the P&P loaded, and run the 
boards through the oven while the P&P is placing the next board, with 
little mid-run downtime.
> Have you considered used equipment? I think that a used machine in good 
> working order would be more affordable.
>   
I have a used Zevatech/Juki P&P I got off of ebay.   I've been playing 
with getting it working right.  It would be good to place larger parts, 
but not smaller ones.   The problem I see is that the used equipment 
seems to be not much less than the new one, and the new ones come with 
some setup help.

Plus there is the whole feeder thing.   I'm still looking for the right 
used P&P, but I sure haven't found it.
> When I made the original post, I was hoping people would suggest auction 
> sites or used equipment dealers, along with recommendations for what could 
> be considered "starter" pick-and-place machines. :)
I would suggest of course ebay, and perhaps smtnet or caeonline or one 
of the similar used brokers.   The wave solder machine I got through one 
of the brokers and I've been pretty happy with it.  But a P&P machine is 
a whole lot more complicated.

-forrest
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