Another example of cost savings on the assembly side is to have a "mirrored"
array.
What this is , is an array of say 6 boards, 3 are in the normal or
"component side" up position
and 3 in the mirrored or solder side up orientation. This works best for a 2
sided reflow
with a selective wave if needed type of layout. Since both sides of the
board can be screen printed then components
placed then reflowed during a single pass down the assembly line, only 1
solder screen is needed and
1 set of pick & place machines and one program for the machine's is needed.
After the 1st pass through
the line, the array is brought back to the start, flipped and then run
through the line again.
After SMD placement, I believe the arrays were then split in half to go thru
the through hole and selective wave process.
This is the preferred method at one of my former employers and it worked
very well for them.
Of course this method doesn't work for all applications, but when it is
used, it can save
a considerable amount of equipment cost, programming cost, floor space
etc...
Just thought I'd toss this out as a possible cost saving method.
Cheers,
Dan
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Chris
Ball
Sent: Friday, July 29, 2005 2:03 PM
To: [log in to unmask]
Subject: Re: [DC] Standard panel size?...
Or 5MM or so inside if it's on a handling edge (breakaway rail or whatever).
An interesting point was brought up earlier about rotation of components
costing money. I don't dispute this, but... can a CEM give a finite cost
difference accounting for this? I lose that argument with purchasing every
time when being driven to squeeze more money out of a product. We can
quantify boards in an array / arrays in a panel.
So for example, we can say that for sure we save 5 cents per board if we
rotate and nest PCB's in an array. We hear about it being a more complicated
set-up, but... If we offer to take a 5 cent hit on the PCB we don't seem to
get back 5 cents in the assembly cost, so we focus on what we can quantify.
-Chris
Terry Kozlyk
<[log in to unmask]> To:
[log in to unmask]
Sent by: DesignerCouncil cc:
<[log in to unmask]> Subject: Re:
[DC] Standard panel
size?...
07/29/2005 01:47 PM
Please respond to
"(Designers Council
Forum)"; Please respond to
Terry Kozlyk
Very good thread !!!
Also, don't forget that when placing your PCB onto a panel to ensure you
don't have connectors which overhand the edge of the panel. Ensure that the
PCB's are rotated such that the connector overhang is toward the inside of
the panel OR ensure that the connectors ( right angle of course ) don't sit
over the edge of the panel. Ensure that the edge of the physical connector
becomes the absolute edge of the PCB within the panel.
Regards
TDK
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Brooks,Bill
Sent: Friday, July 29, 2005 10:00 AM
To: [log in to unmask]
Subject: Re: [DC] Standard panel size?...
Great discussion...
I was talking with one of our board manufacturing vendors and he told me
that they use 18 x 24 and 21 x 24 for quick turns and 20 x 26; 24 x 24 and
24 x 28 in higher volume production for standard lead times.
I still don't exactly understand why but I can speculate that it may be
related to their having a dual approach to supporting their customers
needs... The normal production higher volume work may travel through the
plant in a different way using separate equipment that can handle the larger
panels and the quick turn work may take a path through their equipment that
is optimized for those sizes and processes not commingling with the higher
volume work... hard to say for sure...
For some unknown reason long before I came here we settled on a standard
assembly panel size of 10 X 12 inches and we have been designing our boards
into them like that for the past 5 years that I have been here... It's not
the most efficient use of a 18 X 24 manufacturing panel to be sure... That's
why I am looking at redesigning the panel configuration to be more cost
effective and still compatible with our assembly floor's capabilities...
Higher yields... lower cost per board.
Our solder paste screening machine has a limited depth of about 9.5 inches
of travel and that limits the number of individual boards I can put on the
assembly panel in either axis. Most of the other equipment, pick and place,
washing, wave solder, axial and radial inserters, test equipment, hand
stuffing second op workstations, etc...can handle larger dimensions. The
screening station in our case is the limiting factor. Having a longer panel
than 12 inches here does me no good.
Some folks are making their panels 8.2 X 11.2 inches and fitting them 'four
up' in an 18 x 24 panel with a .75 inch border around the perimeter and a
.100 inch routed separation between them.
Using V-scoring would gain an extra .050 on each edge of the panels if they
weren't routed. This is quite doable since our assembly panels are always
rectangular and with straight edges. We always orient the boards in our
panels in the same direction so the programming for pick and place is easier
and screening and reflow or wave soldering are consistent from board to
board...
Some vendors want more space between the individual assembly panels on their
manufacturing panel and prefer an inch border and .4 between assembly panels
for their tooling, fixtures, holders and test coupons.
Making sure the panel size we end up with is efficient for ANY vendor we use
is really my goal... and that does take a little research to find out what
limiting factors are common among the vendors.
So far it looks like the 8 X 11 size is pretty close to workable for most
any shop and is fairly efficient use of the manufacturing panels they
have... especially the 18 x 24 size...
Then when we do our assembly panel designs we will have to package them into
the 8 X 11 size (or whatever size we finally settle on) with all the needed
fiducials, tooling holes etc...with clearances for machine holders, rails
and such for our assembly equipment designed into them. Then my challenge
will be to get the most efficient use of the space on our assembly panels...
Thanks for the great comments
Bill Brooks - KG6VVP
PCB Design Engineer, C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
Datron World Communications, Inc. _______________________________________
San Diego Chapter of the IPC Designers Council
Communications Officer, Web Manager http://dcchapters.ipc.org/SanDiego/
http://pcbwizards.com
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