I have been designing and populating boards completely by hand with tons of surface mount packages for the past 20 years. In my opinion, installing surface mount devices (SMD) is actually a lot faster and simpler than pin-through-hole (PTH). All it takes is the right tools such as a small iron with small tip such as a Weller EC1302A and the proper size solder such as diameter 0.015" to 0.020" and a nice quality set of tweezers with curved tips (about 70 degrees bend). All you do is lay the PCB flat on the bench, place a bit of solder on one pad for each part, put the solder down and pick up the tweezers, then pick and place each part and tack it into place by that one pad, then put the tweezers down and pick up the solder and go solder all the other pins. There's no leads to bend or feed through, you don't need a PCB holder, you never have to flip the board over to solder, and there's no leads to clip. If I had a small video camera so you could watch me perform this process, it would truly blow your mind just how fast and easy it is to do. Rework is pretty simple also. When I say "I can", I also mean "you can". I can very easily solder SOIC package chips that are 0.05" pitch leads. The passives at 1206 (that's 0.12" x 0.06") are super easy to place and solder by hand. I routinely place 0805 with ease. Since I've been at this sort of thing for a long time, I can reliably solder VQFP packages that have 80 pins around a 10mm square. The lead pitch here is 0.020" or 0.5mm. That's pretty fine so I don't recommend that a beginner attempt it. My point is that you do not have to use solder paste and a mask and a hot plate or oven and all that to install SMT parts at home when you are building only one or a few of some board.
It has been my experience that the general fear of SMT is all in people's heads and it's over hyped. It's really not hard at all and once you attempt it and succeed, you'll be wondering what all of the fuss was about. There's nothing magical about SMT components. They are just chips and resistors and caps like you are used to. They are just a bit smaller and they just don't have wires attached to them and they simply sit directly on the pads. It's no big deal at all.
William Boucher
http://www.biltronix.com
----- Original Message -----
From: Zitt Zitterkopf
To: vectorlist@vectorlist.org
Sent: Saturday, March 03, 2012 12:44 AM
Subject: Re: VECTOR: Wico XY Pattern Generator - It's alive!
I use to feel the same way about SMT designs; however, I’ve recently (last couple of years) begun to appreciate them more than thru hole devices. That are just so easy to assemble when you have some inexpensive equipment. better than hours slaving over a hot iron. a pair of tweezers and some solder paste and your ready for prime time.
Surface mount is not bad at all. In general; for these chips; I have a laser cutter and cut a stencil out of mylar. There are sites on the interwebs that will cut stencils for a low cost. That stencil is then is used to wipe the solder paste into the pads on the board.
Then it’s a matter of heating the board to melt the solder paste. I use a hot plate (target) and a controller (sparkfun). yes; I’ve invested in surface mount; but the barrier to do surface mount is not that steep.
HOWEVER; with the exception of the one –12VDC buck converter; all the other ICs are basically low pitch SO16/8s which are very easy to solder with any somewhat decent soldering iron. With the passives at 603 packages; a little practice should yield good results.
In this case; the thruhole parts are a problem.
1) Most hobby versions of Eagle (the PCB software) limit designs to 3.5x4.5 inches or so. Thru hole may put that over the limit. I seem to recall I was at or near that limit with this design.
2) At least one (the -12V buck converter) IC only comes in surface mount versions. IIRC
Having said that; I see the value for the hobbyist to want thru hole devices... I’ve posted the schematics; as well as the corrections to said schematics (this thread) – so someone could somewhat easily create a thruhole PCB assuming they had the experience.
John
Sent: Friday, March 02, 2012 10:02 PM
To: zittware@hotmail.com
Subject: Re: VECTOR: Wico XY Pattern Generator - It's alive!
I don't know how PCB design software works (would love to have an excuse to learn though), but is converting from a surface mount design to a through hole design as simple as changing a property and having the software figure out the new physical layout? The reason I ask is that surface mount is a real show stopper for me if this is a build it yourself kit. I would gladly pay the additional cost in PCB size if it meant I could get through hole parts so that I could actually build it myself. [deleted]
Thanks,
-Chris
--- On Thu, 3/1/12, Zitt Zitterkopf <zittware@hotmail.com> wrote:
From: Zitt Zitterkopf <zittware@hotmail.com>
Subject: VECTOR: Wico XY Pattern Generator - It's alive!
To: vectorlist@vectorlist.org
Date: Thursday, March 1, 2012, 1:48 AM
Bet most of you forgot about the XY Pattern Generator project... I’m sure some of you thought it was vaporware...
Welp; It took longer than expected; but after several off/on months of debug – I finally got it working.
During debug board#1; I managed to short +12 to +5 frying all the logic.
So I restarted with my second board and built/debugged a section at a time.
Here’s what I posted to KLOV’s forums where I started a picture Worklog:
Several months ago I posted in my Star Trek Captains' Chair worklog that I intended to modernize a old XY Pattern Generator design on the interwebs. Many of the guys on VectorList provided valuable insight into the interworkings of the circuit... and provided many layers of helpful advice.
The result was the following schematics and a set of FabA prototype boards from BatchPCB.com as a dual sided board.
Surface Mount ( yes; I can hear the screams of horror ) as I wanted to minimize PCB size – thereby cost.
If your interested in the prototype schematics; they are here:
http://pinball-mods.com/blogs/wp-content/uploads/2011/11/XYPattern.pdf
I'm pleased to report that tonight I finally debugged the last problem (that I know about).
There is a small list of issues I had to work thru; but for the most part the design worked almost out of the box.
1) The clock generator circuit (3.578MHz xtal) and U1ABC was not "locking". This was due to the buffered logic of the newer 74HC* logic. Some research on the internet indicated I needed a 150pf cap from pin1 U1A to ground to allow the clock generator to excite enough to lock. Another recommendation was to use a Unbuffered HC inverter... which I'll incorporate into the next revision of the schematics.
2) The -12V buck converting power supply wasn't outputting the correct voltage. It'd start out at ~11V.... the drop to ~5V over several minutes. On my debugged board; shorting R26 (10meg ohm) allows the -12V to become rock steady at -11.8V. Unsure here; the Maxim EE sim was very specific on the 10meg ohm value... but the maxim datasheet indicated two modes for VL to operate in. So for now will error on the practical side.
3) The 5V regulator did not have enough copper to heatsink to. Next revision of the FAB will have a large 5V copper heatsink built into the board. For my prototype; I thermal epoxied a small heatsink from a old motherboard onto the top of the regulator to give it some thermal sink.
4) The Linear POT datasheet was missing details regarding the LED side of the POT. One hole was off and will need to be moved.
Things I still need to do:
1) Hook it up to my G08 and align me some guns.
2) check the +12V portion of the buck converter. Right now I'm using the backup +12V linear regulator (U9).
3) Modify schematics and board for FabB (learnings above).
4) Create an enclosure to house the unit.
Nice to haves:
A) Retrofit EPROM sockets to toggle A11 for a 27C32 eprom(s)... allowing for more user designed test patterns.
B) Rename topside adj pots to indicate X and Y.
C) make 3pin jumpers so the jumpers can be mecahnically sound output swing is not shorted
PCB pictures and Oscope captures are posted at the KLOV worklog for your reading enjoyment:
http://forums.arcade-museum.com/showthread.php?t=225710
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Received on Sat Mar 3 15:42:23 2012
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