Diseño PCB

FP

• Anchura pista
  • MIN 12mils
  • PREF 40mils (VCC i GND 40mils)
• Distancia
  • Entre pistas 100mils
  • Pistas y PCB 200mils
  • Componentes 150mils
  • Pad y pista 100mils
• Agujeros
  • 0.8mm para Resistencias de 1/4W

Fabricación casera que consigo

• Anchura pista
  • MIN 20mils
• Distancia
  • Entre pistas 14mils

Manual Kicad - Miguel Pareja

• Módulo
• Pad, vias o isletas
  • Taladros de fijacion
  • Vias
• Pistas
  • Ancho de pista
    • Depende de los amperios que pasan
    • Para corrientes menores a 300 miliamperios, un valor mínimo de ancho de pista de 0,5 milímetros (20mil)
    • Para mayores corrientes, se puede escoger la norma de 0,5 milímetros (20mil) de ancho de pista por cada amperio, como valor límite o mínimo. Algunos autores recomiendan la norma de 1 milímetro (39mil) de ancho de pista por cada amperio para un valor estándar de recubrimiento de cobre de la placa de circuito impreso de 35 micras.
    • La anchura mínima de las pistas de alimentación será de 2 milímetros (78 mil).
  • Separación entre pistas
    • Depende del voltaje que cae en el componente

PCB Layout Tutorial by David L. Jones

http://server.ibfriedrich.com/wiki/ibfwikien/images/d/da/PCB_Layout_Tutorial_e.pdf

• Grid
  • Submultiplos de 100mils (50,25,20,10, 5)
  • Comenzar con 50mils he ir bajando si los componentes tienen que caber en un espacio reducido
• Ancho pistas
• Pads
  • Parametro importante, pad/hole ratio
    • Cada fabricante tiene su ratio
    • Una regla es que el pad tiene que ser 1.8 veces el diametro del hole o al menos 0.5mm mas largo
  • Los pads de las resistencias, diodos, condensadores deben ser redondos de al menos 70mils de diametro
  • Los pads de los DIL (Dual In Line) se hacen ovales
    • 60mils de alto por 90-100mils de ancho
    • El Pin 1 suele ser rectangular para diferenciarlo
  • Los pads de SMD suelen ser rectangulares aunque los empaquetados SOIC suelen usar pads ovales con el pin 1 rectangular
• Vias
  • Profesionalmente se hacen plateando las vias para interconectar las pistas (PTH - Plated Trough Hole)
  • Suelen ser de 0.5-0.7mm
• Clearances
  • 15 mils es un buen espaciado para diseños through hole
  • 10 mils a 8 mils se usa para montajes smd muy densos

For 240V mains on PCB’s there are various legal requirements, and you’ll need to consult the relevant
standards if you are doing this sort of work. As a rule of thumb, an absolute minimum of 8mm (315 thou)
spacing should be allowed between 240V tracks and isolated signal tracks. Good design practice would
dictate that you would have much larger clearances than this anyway.

• Component Placement & Design
  • Lo mas importante de hacer PCBs es colocar bien los componentes. Tanto la facilidad del ruteo de pistas como la calidad electrica de la PCB dependen de la colocación de los componentes. Colocar los componentes es un arte, y cada diseñador hará la misma placa de diferente manera. Igualmente hay unas normas básicas que se deben seguir
    • Divide and place your components into functional “building blocks” where possible.
    • Identify layout critical tracks on your circuit and route them first.
    • Place and route each building block separately, off the board.
    • Move completed building blocks into position on your main board.
    • Route the remaining signal and power connections between blocks.
    • Do a general “tidy up” of the board.
    • Do a Design Rule Check.
    • Get someone to check it

Lets look in more detail at the procedure described above.
We have already looked at the grids and track/pad sizes, these should be the first things that you set up
before you start doing anything. No exceptions!

Many people like to jump straight into placing all the components into what they think is the most optimum
position on the board, all in one hit. Whilst this can work for small circuits, you don’t have much of a hope
when you have more complex circuits with hundreds of components spread across many functional circuit
blocks. Why?, because it’s very easy to run out of “routing space”, which is the room to lay down all your
tracks. If you fix all your component positions and then try to route everything, you can easily paint yourself
into a corner so to speak. Alternatively, if you space the components out too much, you can end up with a
large board that does not make efficient use of space.

The hallmark of an inexperienced designer is a board that has every component evenly spaced out, and then
has thousands of tracks and vias crisscrossing the board. It might work, but it can be ugly and inefficient, not
to mention bigger and more expensive to manufacture.

The best way to start your layout is to get ALL of your components onto the screen first.
If you have a companion schematic package, then the simplest way to do this is to get your PCB program to
import your schematic design and select all the components automatically. This will also be discussed later. If
all you have is a PCB program, then you’ll have to select each component from the library and place them
down manually.

With all the components on screen, you should get a good indication of whether or not your parts will easily fit
onto the size (and shape) of board that you require. If it looks like it’s going to be a tight fit then you know that
you will have to work hard to try and keep the component spacing “tight”, and the tracking as efficient as
possible. If it looks like you have plenty of room then you can be a bit more liberal in your layout. Of course,
if it looks like you have buckleys chance of getting your components on the board, you’ll have to go back to
the drawing board.

Now analyse your schematic and determine which parts of the design can b