Electronic circuit design:
[1] Draw well-formatted schematics
[2] Define operating conditions, moisture condensation, and water ingress
Board geometry:
[1] Define PCB shape, dimensions, and weight.
[2] Make holes for PCB mounting
[3] Make cuts or slots for easy PCB pullout from its assembly
[4] If wires are going to be soldered directly on PCB, the make a setup for strain relief like clamps or zip ties
[5] Make sure that the PCB has only one possibility to mount in the device by making slots or non-symmetric guides.
[6] Use PCB cut for isolation between high and low voltage
[7] Make holes under IC sockets, to eject ICs easily from the back
[8] Design for penalization (multiple PCBs in one shot)
Layers:
[1] Start your design with single layer PCB first. If one layer is not enough, then move to two layers and so on.
[2] If you are going to control high power loads, then you may use PCB with thicker copper layer (2 oz/ft2 instead of 1 oz/ft2)
Components location:
[1] Design to use electronic components that are available in your local market
[2] You may use some THT components as SMD
[3] Divide your design into modules and locate inputs and outputs of each module
[4] Sort modules based on the connections
[5] Put power components on one layer and control components on the other layer
[6] Define the orientation at which the PCB will operate to place hot components at the top.
[7] Place service components always accessible as possible like: memory cards, SIM cards, batteries, fuses, varistors, potentiometers, ... etc
[8] Place components as near as possible to other related components
[9] ِAlign or array components of the same type and package
[10] Put spare components in the PCB (such as a spare fuse)
[11] Use sockets for components expected to be replaced or upgraded, or if you afraid of overheating IC chips during soldering
[12] Make your design smarter, so it can be used to produce different variants by just adding or removing few components
[13] Place micro-controller in the middle of the PCB.
[14] Make status LEDs that till you that the PCB is alive
[15] Consider ICSP pins to reprogram your micro-controller in the future
[16] If your PCB has no user-interface, then make an external debugging interface
[17] Consider using external removable jumpers to enable or disable a function
[18] Save areas for TO22 package layed flat
[19] Consider heat sinks orientation
[20] Use PCB copper area as heat sink for heat-dissipating components
[21] Use one large screw terminal block instead of multiple small blocks if they are going to be placed beside each other because it is difficult to align them
[22] Place components in locations where it is easy to de-solder. For example, don't place and SMD component trapped between high components from all directions.
Tracks:
[1] Check the manufacturing capabilities of the PCB manufacturer you are going to deal with first. If you plan to etch this PCB manually, then use large tracks and large track spacing.
[2] For power tracks, calculate track width so that the voltage drop is accepted and track temperature is maintained constant at given ambient conditions and cooling method
[3] Use through hole components to jump over tracks if you have limited number of layers
[4] If you have limited number of layers, use wire jumpers
[5] Keep enough area empty of tracks around holes so screw head or hexagonal spacer will not affect them
[6] Avoid putting pads in the way of a track
[7] Use decoupling capacitors just beside the IC
[8] Avoid using stubs
[9] Use low impedance tracks for high frequency lines by making shorter paths and wider tracks
[10] Reduce number of bends in the track as possible
[11] Use shorter paths
[12] Use very short paths for power lines used as relays to get compact PCB
[13] Use short spikes between components and large tracks
[14] Don't use right angle path
[15] Don't use acute angle paths
[16] Maintain the parallelism and equi-spacing of data lines
[17] Keep enough clearance between tracks
[18] Avoid using loopy tracks (antenna)
[19] Use ground plane to connect all ground pins and avoid the hassle of connecting them
[20] Use ground plane carefully. If you are going to control high power loads and use ground plane, make sure that there is enough area for current to flow
[21] Get rid of thin islands
[22] If ground plane is used, keep areas under high voltage components void (clear of copper) to avoid dielectric failure.
[23] Keep areas under transformers empty of tracks
[24] Avoid passing tracks under components or IC chips as possible for easy track tracing and repair in the future
[25] Use star connection for 5V instead of daisy chain
[26] Use parallel tracks for sensors to cancel noise
[27] Avoid passing tracks between pads
Labeling:
[1] Use unique labels for all components
[2] Label component code if there is enough space
[3] Use component code if it only has no alternatives or it is not allowed to be replaced with another component
[4] As possible, put labels beside components, not under them
[5] Try to avoid placing labels on tracks
[6] Create labels in ascending way from the top-left corner to the bottom-right corner so that they can be reached easily by eye sweeping
[7] Label soldering pads to test connectivity
[8] Create label for revision number and production date
[9] Create label for contact details: company name, website address, phone number, or email
[10] Create label for disposal method
Pads:
[1] Consider test pads. Test pads are flat blind pads where they are expected to be used for testing and troubleshooting purposes.
[2] Consider golden fingers
[3] Consider connector pads. Connector pads are this pads that can be cut to permanently enable or disable a function
[4] Keep enough distance between soldering pad and track
[5] Snap all pins to perforated weaver board, so you can prototype easily
[6] Make sure that no pins will touch component in the back.
[7] Avoid over-sizing of through holes
[8] Use thin pads as fuses
[9] via under SMD IC chip to save space
Prototyping:
[1] Print your PCB to paper and place components on it to check matching of the footprint
[2] Try your circuit on bread board
[3] Visualize your design in 3D
[4] Get rough figure for the price of the PCB
Additional references:
https://en.wikipedia.org/wiki/Printed_circuit_board
http://www.robotroom.com/PCB-Layout-Tips.html
[1] Draw well-formatted schematics
[2] Define operating conditions, moisture condensation, and water ingress
Board geometry:
[1] Define PCB shape, dimensions, and weight.
[2] Make holes for PCB mounting
[3] Make cuts or slots for easy PCB pullout from its assembly
[4] If wires are going to be soldered directly on PCB, the make a setup for strain relief like clamps or zip ties
[5] Make sure that the PCB has only one possibility to mount in the device by making slots or non-symmetric guides.
[6] Use PCB cut for isolation between high and low voltage
[7] Make holes under IC sockets, to eject ICs easily from the back
[8] Design for penalization (multiple PCBs in one shot)
Layers:
[1] Start your design with single layer PCB first. If one layer is not enough, then move to two layers and so on.
[2] If you are going to control high power loads, then you may use PCB with thicker copper layer (2 oz/ft2 instead of 1 oz/ft2)
Components location:
[1] Design to use electronic components that are available in your local market
[2] You may use some THT components as SMD
[3] Divide your design into modules and locate inputs and outputs of each module
[4] Sort modules based on the connections
[5] Put power components on one layer and control components on the other layer
[6] Define the orientation at which the PCB will operate to place hot components at the top.
[7] Place service components always accessible as possible like: memory cards, SIM cards, batteries, fuses, varistors, potentiometers, ... etc
[8] Place components as near as possible to other related components
[9] ِAlign or array components of the same type and package
[10] Put spare components in the PCB (such as a spare fuse)
[11] Use sockets for components expected to be replaced or upgraded, or if you afraid of overheating IC chips during soldering
[12] Make your design smarter, so it can be used to produce different variants by just adding or removing few components
[13] Place micro-controller in the middle of the PCB.
[14] Make status LEDs that till you that the PCB is alive
[15] Consider ICSP pins to reprogram your micro-controller in the future
[16] If your PCB has no user-interface, then make an external debugging interface
[17] Consider using external removable jumpers to enable or disable a function
[18] Save areas for TO22 package layed flat
[19] Consider heat sinks orientation
[20] Use PCB copper area as heat sink for heat-dissipating components
[21] Use one large screw terminal block instead of multiple small blocks if they are going to be placed beside each other because it is difficult to align them
[22] Place components in locations where it is easy to de-solder. For example, don't place and SMD component trapped between high components from all directions.
Tracks:
[1] Check the manufacturing capabilities of the PCB manufacturer you are going to deal with first. If you plan to etch this PCB manually, then use large tracks and large track spacing.
[2] For power tracks, calculate track width so that the voltage drop is accepted and track temperature is maintained constant at given ambient conditions and cooling method
[3] Use through hole components to jump over tracks if you have limited number of layers
[4] If you have limited number of layers, use wire jumpers
[5] Keep enough area empty of tracks around holes so screw head or hexagonal spacer will not affect them
[6] Avoid putting pads in the way of a track
[7] Use decoupling capacitors just beside the IC
[8] Avoid using stubs
[9] Use low impedance tracks for high frequency lines by making shorter paths and wider tracks
[10] Reduce number of bends in the track as possible
[11] Use shorter paths
[12] Use very short paths for power lines used as relays to get compact PCB
[13] Use short spikes between components and large tracks
[14] Don't use right angle path
[15] Don't use acute angle paths
[16] Maintain the parallelism and equi-spacing of data lines
[17] Keep enough clearance between tracks
[18] Avoid using loopy tracks (antenna)
[19] Use ground plane to connect all ground pins and avoid the hassle of connecting them
[20] Use ground plane carefully. If you are going to control high power loads and use ground plane, make sure that there is enough area for current to flow
[21] Get rid of thin islands
[22] If ground plane is used, keep areas under high voltage components void (clear of copper) to avoid dielectric failure.
[23] Keep areas under transformers empty of tracks
[24] Avoid passing tracks under components or IC chips as possible for easy track tracing and repair in the future
[25] Use star connection for 5V instead of daisy chain
[26] Use parallel tracks for sensors to cancel noise
[27] Avoid passing tracks between pads
Labeling:
[1] Use unique labels for all components
[2] Label component code if there is enough space
[3] Use component code if it only has no alternatives or it is not allowed to be replaced with another component
[4] As possible, put labels beside components, not under them
[5] Try to avoid placing labels on tracks
[6] Create labels in ascending way from the top-left corner to the bottom-right corner so that they can be reached easily by eye sweeping
[7] Label soldering pads to test connectivity
[8] Create label for revision number and production date
[9] Create label for contact details: company name, website address, phone number, or email
[10] Create label for disposal method
Pads:
[1] Consider test pads. Test pads are flat blind pads where they are expected to be used for testing and troubleshooting purposes.
[2] Consider golden fingers
[3] Consider connector pads. Connector pads are this pads that can be cut to permanently enable or disable a function
[4] Keep enough distance between soldering pad and track
[5] Snap all pins to perforated weaver board, so you can prototype easily
[6] Make sure that no pins will touch component in the back.
[7] Avoid over-sizing of through holes
[8] Use thin pads as fuses
[9] via under SMD IC chip to save space
Prototyping:
[1] Print your PCB to paper and place components on it to check matching of the footprint
[2] Try your circuit on bread board
[3] Visualize your design in 3D
[4] Get rough figure for the price of the PCB
Additional references:
https://en.wikipedia.org/wiki/Printed_circuit_board
http://www.robotroom.com/PCB-Layout-Tips.html
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