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Kai Klaas
11/08/05 08:03
Modified:
  11/08/05 08:04

Read: 1101 times
Germany


 
#103418 - You need a solid ground plane
Responding to: Suresh R's previous message
Suresh said:
I have used the top layer copper pour to connect the ground node of all components.The top layer copper pour is stitched to the bottom layer copper pour through vias.

The idea of having a solid ground plane is to provide the least amount of impedance on the ground routing. But stitching together single local ground areas by some vias is a violation of this idea, because vias heavily increase the impedance again. A ground plane does only work if it is really solid! Even if you only make some interruptions and gaps then the effect is a huge suffer in performance.
Have a look at

http://www.8052.com/forum/read.phtml?id=103336

to see what a solid ground plane is for.
If you "must" use a double sided board, then the best way to get the circuit working, is to use a solid ground plane on the bottom side (especially when using SMDs), and running all the signals on the top side (component side). If signals must cross each other, then use bridges (wires) on the bottom side placed over the solid ground plane, without interrupting it! Keep the ground plane at the bottom side always as solid as ever possible!
Each ground pin of SMDs is connected to ground plane on bottom side by at least two vias placed directly at according ground pin.
This methode only works with simple boards, where the pinout of chips allows a bus wise routing of address and data buses and if only chips are used which aren't faster than 74HCMOS logic. Keep also in mind, that doing the artwork for such a construction can be more expensive than using a multilayerboard from the start. (This is only true if artworker's salary is higher than manufacturing costs of multilayer.)

Kai

List of 16 messages in thread
TopicAuthorDate
two layer PCB      Suresh R      11/04/05 23:56      
   +5VDC also drives PhotoMOS relays      Suresh R      11/05/05 00:13      
   Solid ground plane is needed!      Kai Klaas      11/06/05 05:18      
      what i have done is      Suresh R      11/07/05 10:19      
         what you have done ...      Andy Peters      11/07/05 11:36      
            Thermal relief's      Suresh R      11/08/05 03:09      
               You need a solid ground plane      Kai Klaas      11/08/05 08:03      
                  I want the best money can buy, but do no      Erik Malund      11/08/05 08:22      
                  Thermal relief in PCB's      Suresh R      11/08/05 11:24      
                     An illustration...      Kai Klaas      11/09/05 06:26      
                        went through the design but      Suresh R      11/10/05 04:46      
                           Thermal reliefs were demonstrated      Kai Klaas      11/10/05 05:30      
                           who are you posting to????      Erik Malund      11/10/05 06:14      
               thermal reliefs only ease soldering        Sasha Jevtic      11/08/05 12:37      
                  Resistance calculation for thrmal relief      Suresh R      11/08/05 22:35      
                     you better read .....        Abhishek Singh      11/10/05 05:56      

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