IC DIP

It seems a sensible way to do it for mechanical insertion. The robot can get a good grip by squeezing the pins to the proper width. As an added plus, the pins would likely spring back enough to hold the part in place until it's soldered. I don't really know this to be a fact, but it at least sounds plausable. ;-)

One also used to use IC insertion tools that had a plunger running in a fixed-width slot--it held the DIPs the same way.

This scheme has the very important advantage that it makes sure that the leads are in exactly the right place for insertion without bending. The leads are very stiff in the along-package direction, so that's less of a problem, but the lateral position depends on a not-very-precise lead frame bending operation.

This way, you make the tooling accurate, once, and the spring force in the leads makes sure that all the pin positions are accurate thereafter.

Cheers,

Phil Hobbs

I've seen these auto-insertion machines in operation (both DIP and surface mount). Very cool and fun to watch. The speed is AMAZING, but people who work with them everyday probably think they're slow.(?)

One of the machines I saw used what looked like a whole bunch of bright red LED's. And you could feel the heat. (This was on a surface mount line.) I don't know if that was a pre-heater, or the thing doing the actual soldering.

Anyway, when you see how fast these work, you understand there's no slop in the mechanicals. I wish I had a video to share.

-mpm

The big mistakes were making the parts symmetrical, numbering the pins circularly, and putting Vcc and ground in the corners.

John

It's easier to set up a machine if you know up front that it has to sqeeze

Tam

John Larkin wrote

I can see the problem with symmetry, but what's wrong with the numbering or the position of the power pins?

robert

Yes they are. People who are interested in machinery find them fascinating. A friend spent hours just watching the chip shooter work once! Other people don't have the time of day for them. They don't even look at them as they are hammering parts down.

The speed is AMAZING, but people who

One of our pick and place machines (turret based chip shooter) can place parts at a sustained 0.15 seconds per part. After using it for a while it does seem much slower. Going back and using one of our older machines (also turret based chip shooter) that places parts at 0.25 seconds per part makes the machine look so slow.

On an SMT line, the only major heat source should be the reflow oven. They can throw some heat off. The power consumption is usually between 10 and 20 kW after startup (can be much more during start up) depending on oven size, speed, loading and profile, along with some other things like insulation and ventilation rate.

When placing parts with a 3 sigma accuracy of 0.08 mm at a rate of 0.15 seconds a part after everything is said and done, the machines have to be very tight. One machine is capable of 0.025 mm accuracy at 3 sigma, but is significantly slower.

I have some that will be on our website when its updated in a few months, unfortunately, this thread will likely be forgotten about by then.

Since overall, very little quantity of DIPs were stuffed by had, people making DIPs optimized them to be machine placed by machines called "DIP Inserters". This meant the machine would squish the pins a bit so they would all be parallel and inline. Once the machine inserted the part, the leads would spring back some and hold it in place.

Now most through hole is slowly dying along with DIPs as SMT is taking over.

For the stuff that needs smaller productions of PCB's with DIP's that are not worth putting on an insertion machine, automatic lead formers are available that bend the leads vertical and parallel. We have such a machine and it works well and is very fast.

We would be better off if the power pins where like on a quad op-amp of a pair near the center on one side. The inductance of the ground and Vcc path is an issue when you get to high speeds.

As far as I can see it, all simple numbering systems are about equal.

Jeff,

Please post a pointer to your website when you get it updated with something descriptive in the subjet line.

I've seen more and more chips with symmetrical power pins in the center of the part. If you insert it backwards, at least the Vdd/Vss pins are connected right.

Probably still fry the chip though :-P

distaance to the die is too far.

cf lm339. power pins closer to die, easier to decouple. also the power trace forms a guard between siglals

Bye. Jasen

Wouldn't it be easiest (and best) to put the supply pins on an end or side (e.g. 3842, 555)?

Tim

-- "Librarians are hid> > John Larkin wrote

Engineers didn't used to be dummies ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

aarg! lm324

Bye. Jasen

Back when 2-layer boards were the norm and speeds were slower, having the pins consistently in the corners allowed for a nice Vcc/GND grid layout on top and bottom using traces too fat to go between DIP pins.

Best regards, Spehro Pefhany

IIRC, the reason most TTL power pins were put in the corners was to make wiring easier. One and two sided boards were all the rage then.