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I am trying to confirm the right orientation for all the packages I am using in Eagle before sending for pick and place assembly. After reading a bit, I understand that there is no standard from one chip company to another.

My question is simple: can I know for sure the proper orientation based on the way the chip is positioned in the reel ?

SOT25 package I want to know rotation 0 orientation

Looking at the way leds are packaged, and knowing that rotation 0 for leds is cathode on the left and anode on the right, I would tend to think that I can get the rotation 0 orientation by looking at chip with the holes on the left: is that correct ?enter image description here

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  • \$\begingroup\$ By and large, don't worry about it. As long as all your rotation values are consistent for each component (e.g. all 0603 resistors use same rotation origin), the assembly house will deal with ensuring correct rotation. \$\endgroup\$ Mar 16, 2018 at 19:57
  • \$\begingroup\$ I know that there is a check by manufacturers and that they will manually correct rotation or position issues. I would feel more comfortable to know there is minimum manual intervention the day I go in production for a large batch. \$\endgroup\$
    – AlexP
    Mar 16, 2018 at 20:37
  • \$\begingroup\$ They are used to fixing all this stuff and it will be built into your setup fees or lot price. Put your effort into minimizing the number of distinct footprints (affects setup) and distinct components (affects the number of feeders). If you can use two 10K resistors rather than one 4.7K and one 10K (without significant compromise) it is better. \$\endgroup\$ Mar 16, 2018 at 23:42

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It's also worth considering the direction the board passes through the pick-and-place/wave solder line. In my experience, the pick-and-place programmers can handle the part rotation issue when they set up their programs.

However, ICs, especially those with fine pin-pitch, should generally be sent through the wave solder process with pins perpendicular to the wave. Otherwise, solder bridges between pins are much more likely to form, ruining your PCB assembly or setting you up for lots of rework.

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  • \$\begingroup\$ About ICs and wave, to confirm: you mean that orientation should be such as pins on the same side are soldiered one after the other and not all a time. Is that correct? \$\endgroup\$
    – Julien
    Apr 20, 2021 at 7:46
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    \$\begingroup\$ No, the opposite. If the wave is oriented like | and the pins are oriented like =, the pins will approach the wave like so: = | ... after passing the wave: | = ... Solder surface tension will pull solder across the pins in the direction of the board movement, so you're less likely to see solder bridges. If you were to run the pins through with pins parallel to the wave like so: ii | ....... | ii , surface tension will drag solder from the first pin to hit the wave to the next pin. The finer the pitch, the more likely the solder bridge. \$\endgroup\$
    – Bort
    Apr 21, 2021 at 13:19
  • \$\begingroup\$ In other words, all the pins on one side of, say, a DIP or SOIC part will be soldered at once. A decently designed part shouldn't experience any catastrophic thermal shock when doing it this way, and the datasheet will show you the proper solder temperature profile for successfully soldering the part. \$\endgroup\$
    – Bort
    Apr 21, 2021 at 13:21
  • \$\begingroup\$ That makes sense but obviously, some components have pins on the four sides... \$\endgroup\$
    – Julien
    Apr 21, 2021 at 13:26
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    \$\begingroup\$ True. In that case, where I work, we typically try to have all the Pin 1 markers pointing in the same direction and experiment a bit with the soldering process. We typically try to do as few pin-dense parts on the wave side of the PCB as possible for this very reason. \$\endgroup\$
    – Bort
    Apr 21, 2021 at 13:28

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