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Is there any written specification for the orientation of components on a manually assembled PCB, including both THT and SMT passive components?

'Manually' because machines can be easily setup to place components consistently however people need to be instructed to do so.

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  • \$\begingroup\$ I think you might do better being more specific. \$\endgroup\$
    – Andy aka
    Sep 9, 2021 at 9:11
  • \$\begingroup\$ Why not use a tweezer instead of hand placing? Are you using SMD components, if yes whats the package size. \$\endgroup\$ Sep 9, 2021 at 9:25
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    \$\begingroup\$ @abunkickabhi I am sure tweezers are used, it's just usual to refer to such a method as "hand placed" or "hand picked" \$\endgroup\$
    – user16222
    Sep 9, 2021 at 9:35
  • \$\begingroup\$ Don't know any written rules. If developing your own, consider ability to get soldering iron into tight spaces... \$\endgroup\$
    – user16324
    Sep 9, 2021 at 14:17

2 Answers 2

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A relevant specification is IPC-A-610: Acceptability of Electronic Assemblies, specifically section 7.1.1. Essentially, it states that non-polarized components on the board should all read the same way, e.g. left-right and top-bottom, but the board is not considered defective unless the orientation of the component makes the circuit non-functional. The standard also has an overarching clause that specific written requirements for an assembly supersede anything that may be printed in the standard, which really means that you can specify whatever you want to. I personally try to have the markings on my components read in the same direction as the component designators on the board, so left-to-right and bottom-to-top.

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Depends on component. Resistors are symmetric. So direction doesn't matter. So are inductors (coils). Ceramic capacitors are symmetric too (SMD or disk through-hole). Tantalum and electrolytic capacitors are polarized, they have a + and a -. Diodes, obviously, have a direction. Ferrite beads are symmetric.

Basically, if some component is not symmetric, there should be some marking that will allow you to distinguish its sides, such as on electrolytic caps (longer/shorter lead and markings on the case itself).

But how does this have anything to do with hand placing? I mean, why would it matter if it's a machine or a human placing them. You care about electrical performance of the device you place. It doesn't matter if it's amazon alexa, robot, machine, human or your cat placing the components.

Or maybe I misunderstood your question?

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    \$\begingroup\$ It is easier to read the PCB if component legends are readable and all the resistor bands are read left to right or top to bottom. It is a convention to follow this tidiness but is there any document about this from IEC, DIN, BS, ISO, NASA, etc? \$\endgroup\$
    – Rob Kam
    Sep 9, 2021 at 10:04
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    \$\begingroup\$ The general convention is "make it easy to understand and service" \$\endgroup\$
    – Ilya
    Sep 9, 2021 at 10:15

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