Diferencia entre revisiones de «Diseño PCB»

De Proyectos
Ir a la navegación Ir a la búsqueda
← Edición anteriorEdición siguiente →
Línea 66: Línea 66:
*Component Placement & Design
*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
**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
***Set your snap grid, visible grid, and default track/pad sizes.
***Throw down all the components onto the board.
***Divide and place your components into functional “building blocks” where possible.
***Divide and place your components into functional “building blocks” where possible.
***Identify layout critical tracks on your circuit and route them first.
***Identify layout critical tracks on your circuit and route them first.
Línea 74: Línea 76:
***Do a Design Rule Check.
***Do a Design Rule Check.
***Get someone to check it
***Get someone to check it
<pre>
Lo primero que hay que hacer es establecer el grid y los tamaños de las pistas y los pads
Un error común es colocar todos los componentes de golpe en el PCB. Esto puede ocasionarte problemas, como por ejemplo quedar sin espacio para las pistas o dejar espacio "muerto" quedandote una PCB grande y desaprovechada.
Una tipica PCB de novato está con los componentes muy espaciados y hay cientos de pistas y vias atravesando la placa.
La mejor manera de empezar es haciendo un volcado de todo el esquema.
Con todos los componentes en la pantalla y teniendo el tamaño de la PCB puedes ver si tienes que "currarte" una disposición estrecha y eficiente de los componentes o si puedes ser un poco mas liberar en la disposición de los componentes.
Now analyse your schematic and determine which parts of the design can be broken up into “building blocks”.
Often this is fairly obvious. Say for example you have a complex looking active filter in your circuit. This
would typically have a single input line and a single output line, but it will have lots of components and
connections as part of the filter. This is a classic “building block” circuit, and one that lends itself well to
combining all of these parts together in the same location. So you would grab all of these parts and start to
rearrange them into their own little layout off to one side of your board. Don’t worry too much about where the
actual block goes on your board yet.


You will also need to partition off electrically sensitive parts of your design into bigger blocks. One major
example is with mixed digital and analog circuits. Digital and analog just do not mix, and will need to be
physically and electrically separated. Another example is with high frequency and high current circuits, they
do not mix with low frequency and low current sensitive circuits. More about this later.


<pre>
As a general rule, your components should be neatly lined up. Having ICs in the same direction, resistors in
Lets look in more detail at the procedure described above.
neat columns, polarised capacitors all around the same way, and connectors on the edge of the board. Don’t
We have already looked at the grids and track/pad sizes, these should be the first things that you set up
do this at the expense of having an electrically poor layout, or an overly big board though. Electrical
before you start doing anything. No exceptions!
parameters should always take precedence over nicely lined up components.


Many people like to jump straight into placing all the components into what they think is the most optimum
Symmetry is really nice in PCB design, it’s aesthetically pleasing and just “looks right”. If you have something
position on the board, all in one hit. Whilst this can work for small circuits, you don’t have much of a hope
like two identical building block circuits side by side, and one is laid out slightly differently, it sticks out like a
when you have more complex circuits with hundreds of components spread across many functional circuit
sore thumb.
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
If you have placed your components wisely, 90% of your work will be done. The last 10% should just be
has thousands of tracks and vias crisscrossing the board. It might work, but it can be ugly and inefficient, not
joining the dots so to speak. Well, not quite, but good placement is a good majority of your work done.
to mention bigger and more expensive to manufacture.
Once you are happy with the component placements, you can start to route all the different building blocks
separately. When finished, it is then often a simple matter to move and arrange the building blocks into the
rest of your design.


The best way to start your layout is to get ALL of your components onto the screen first.
The Design Rule Check (DRC) will be covered later, but it is an essential step to ensuring that your board is
If you have a companion schematic package, then the simplest way to do this is to get your PCB program to
correct before manufacture. A DRC basically checks for correct connectivity of your tracks, and for correct
import your schematic design and select all the components automatically. This will also be discussed later. If
widths and clearances.
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
Getting someone to check your board may sound like an overly bureaucratic process, but it really is a vital
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
step. No matter how experienced you are at PCB design, there will always be something you overlooked. A
you will have to work hard to try and keep the component spacing “tight”, and the tracking as efficient as
fresh pair of eyes and a different mindset will pick up problems you would never see.
possible. If it looks like you have plenty of room then you can be a bit more liberal in your layout. Of course,
If you don’t have anyone to check your board over and don’t have DRC capability, then you’ll have to do it
if it looks like you have buckleys chance of getting your components on the board, you’ll have to go back to
yourself. Get a printout of your schematic and a highlighter pen. Now, compare every single electrical “net”
the drawing board.
connection on your board with the schematic, net by net. Highlight each net on the schematic as you
complete it. When you are finished, there should be no electrical connections left that aren’t highlighted. You
can now be fairly confident that your board is electrically correct.


Now analyse your schematic and determine which parts of the design can b
</pre>
</pre>

Revisión del 19:00 9 dic 2014

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
      • Set your snap grid, visible grid, and default track/pad sizes.
      • Throw down all the components onto the board.
      • 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
Lo primero que hay que hacer es establecer el grid y los tamaños de las pistas y los pads
Un error común es colocar todos los componentes de golpe en el PCB. Esto puede ocasionarte problemas, como por ejemplo quedar sin espacio para las pistas o dejar espacio "muerto" quedandote una PCB grande y desaprovechada.
Una tipica PCB de novato está con los componentes muy espaciados y hay cientos de pistas y vias atravesando la placa.
La mejor manera de empezar es haciendo un volcado de todo el esquema.
Con todos los componentes en la pantalla y teniendo el tamaño de la PCB puedes ver si tienes que "currarte" una disposición estrecha y eficiente de los componentes o si puedes ser un poco mas liberar en la disposición de los componentes.


Now analyse your schematic and determine which parts of the design can be broken up into “building blocks”.
Often this is fairly obvious. Say for example you have a complex looking active filter in your circuit. This
would typically have a single input line and a single output line, but it will have lots of components and
connections as part of the filter. This is a classic “building block” circuit, and one that lends itself well to
combining all of these parts together in the same location. So you would grab all of these parts and start to
rearrange them into their own little layout off to one side of your board. Don’t worry too much about where the
actual block goes on your board yet.

You will also need to partition off electrically sensitive parts of your design into bigger blocks. One major
example is with mixed digital and analog circuits. Digital and analog just do not mix, and will need to be
physically and electrically separated. Another example is with high frequency and high current circuits, they
do not mix with low frequency and low current sensitive circuits. More about this later.

As a general rule, your components should be neatly lined up. Having ICs in the same direction, resistors in
neat columns, polarised capacitors all around the same way, and connectors on the edge of the board. Don’t
do this at the expense of having an electrically poor layout, or an overly big board though. Electrical
parameters should always take precedence over nicely lined up components.

Symmetry is really nice in PCB design, it’s aesthetically pleasing and just “looks right”. If you have something
like two identical building block circuits side by side, and one is laid out slightly differently, it sticks out like a
sore thumb.

If you have placed your components wisely, 90% of your work will be done. The last 10% should just be
joining the dots so to speak. Well, not quite, but good placement is a good majority of your work done.
Once you are happy with the component placements, you can start to route all the different building blocks
separately. When finished, it is then often a simple matter to move and arrange the building blocks into the
rest of your design.

The Design Rule Check (DRC) will be covered later, but it is an essential step to ensuring that your board is
correct before manufacture. A DRC basically checks for correct connectivity of your tracks, and for correct
widths and clearances.

Getting someone to check your board may sound like an overly bureaucratic process, but it really is a vital
step. No matter how experienced you are at PCB design, there will always be something you overlooked. A
fresh pair of eyes and a different mindset will pick up problems you would never see.
If you don’t have anyone to check your board over and don’t have DRC capability, then you’ll have to do it
yourself. Get a printout of your schematic and a highlighter pen. Now, compare every single electrical “net”
connection on your board with the schematic, net by net. Highlight each net on the schematic as you
complete it. When you are finished, there should be no electrical connections left that aren’t highlighted. You
can now be fairly confident that your board is electrically correct.
Obtenido de «https://wiki.erikcrane.com/index.php?title=Diseño_PCB&oldid=4654»