All IC's the same direction

Is it still a big no no to turn an IC 180 Deg around to allow for direct routing as it was years ago. Back then all chips had to face the same way or the world would come to an end.

I think this had more to do with the old pick and place machines that couldn't rotate a part and had to have them loaded backwards. The end of the world problem was a result of the operators (that barely spoke English) had to have step by step instructions, and would still install the IC tubes in the wrong direction (namely because they were told to always insert the tubes with the "dot" towards the machine).

With the machines now days, they have vision systems, can rotate parts, and place them way faster and more accurately. I can't believe the number of times I saw DIP packages with pins folded under the device instead of going through the holes.

FlapJack said:

Is it still a big no no to turn an IC 180 Deg around to allow for direct routing as it was years ago. Back then all chips had to face the same way or the world would come to an end.

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I don't know, but I did that once about 20 years ago and four earthquakes occured and two airplanes crashed. I quickly re-aligned the ICs correctly, and the earth settled down. Proceed at your own peril.

Oh, and don't get me started on the shipping and receiving that would take all the parts out of their tubes and trays (PGA pin-grid-arrays for you youngsters) and COUNT them on non-ESD approved tables! We had problems with both dead parts and bent pins. Besides the problem of having them placed back inside the tubes and trays every which way, but the SAME way!

Some decades ago it was very usual to have dozens of PTH IC's at a single PCB, most of them having the same package type ( e.g DIL 300mils ), and an alignment would make much more sense in terms of maintenance, become easiest to find some specific device at a giant board. Nowardays, there are not so much IC's, and most of them encapsulated with different footprints. In addition, the maintenance activity is not part of the current trend of anymore, so that the aesthetic arrangement of components, althouh recommended, is not any issue at all for the pratical point of view.

More importantly than maintenance was the manufacturing issue I've already addressed. Even manual insertion of the ICs was a problem if there were parts that were rotated 180 degrees. ICs in DIP packaging always had power in the highest numbered pin and ground in the middle pin number, so if you rotated them 180 they would BLOW UP (end of the world, or at least the end of your career at that company!).

I actually know this because back then our building had a manufacturing line custom built into our facility to build our boards, we had a pick and place machine along with a wave soldering machine that was something like 1.5 ft wide and 10 ft long filled with molten solder. A board cleaning line, conformal coating line. I regularly had to help the technicians to debug any issue that came up with a new batch of boards. In some cases that was due to rotate parts that were now dead, botched rework, bent pins, missing solder, broken parts, you name it I'd probably seen it.

Like I said earlier, vision systems, registration markings, rotation capabilities, and very few if any parts handled manually, means less need for any orientation requirements, besides those for layout.

I have always laid out SMD based PCBs based firstly on the electrical connectivity, I always layout for reduced loop areas especially for feedback loops etc. I will rotate a component to 45 degrees if it makes the layout better and don't concern myself with the orientation of any component, with pick and place and automatic optical inspection it is not an issue...
In't old days when board assembly involved a lot of human labour and human inspection things were different, now any angle any orientation...

You had just observed an extremely important point, that's exactly what I do too often. The more we know electronics in deep, and the more critical are the specifications of the project, we are concerned for signal integrity rather than style aspects of the layout.

My layouts always look pretty, even if the ICs and other packages are in random directions, a good layout will look neat and uncluttered and flow smoothly, a bad layout will not...

marce said:

I have always laid out SMD based PCBs based firstly on the electrical connectivity, I always layout for reduced loop areas especially for feedback loops etc. I will rotate a component to 45 degrees if it makes the layout better and don't concern myself with the orientation of any component, with pick and place and automatic optical inspection it is not an issue...
In't old days when board assembly involved a lot of human labour and human inspection things were different, now any angle any orientation...

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DIP is not dead and there is something to be said for sockets. Would you worry about orientation for this type of board today.

I always orient my ICs the same way, and with multilayer boards there is really no excuse for random orientation.
It makes servicing a LOT more straightforward as well.

I have very strong feelings that every circuit board designer should be forced to serve at least one year of hard labour on the chain gang, doing component level board repairs.
And another year as a slave on the production line loading boards.
A whole bunch of small details you probably never thought of start to become of vital significance.

FlapJack said:

DIP is not dead and there is something to be said for sockets. Would you worry about orientation for this type of board today.

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In the commercial world DIP is all but dead.... I may do two layouts a year that use DIP devices. Today with AOI I don't care about component orientation I care about the electrical operation of the circuit that is my primary concern.

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Warpspeed said:

I always orient my ICs the same way, and with multilayer boards there is really no excuse for random orientation.
It makes servicing a LOT more straightforward as well.

I have very strong feelings that every circuit board designer should be forced to serve at least one year of hard labour on the chain gang, doing component level board repairs.
And another year as a slave on the production line loading boards.
A whole bunch of small details you probably never thought of start to become of vital significance.

Click to expand...

Out of date these days, EMC and signal integrity concerns are paramount and with AOI pick and place this is not necessary and often when I see designs done this archaic way they are a compromise electronically, and have never had any production issues with doing it like this... In fact your the only person I have heard for many years have this view. Having multi layer PCBs should not be an excuse for bad placement....

Modern pick & place machines rotate parts easily, so you can choose any angle you like, although it's common to restrict it to multiples of 45°. My TM220A rotates parts between -180° and 180° with an accuracy of 1°.

For through hole parts, make sure to use a socket that indicates the location of pin 1, or mark it on the text overlay to avoid erroneous orientation of the part.