PCB Jargon Burster.

[lord loh.]

I have recently been usign a PCB layout software and had a lot of confusion with several terms.

viz. route track pad pore via assy silkscreen etc.

These wew a few I came across. There might be more. Can anyone tell me what they are or point me to a PCB glossary or something. And tell me of things that I might have missed....

Thank you.

 

[EdwardM]

Hi Bharath

to try and explain at least some of it:

Track: is the copper foil left after the etching process and is literally the piece of copper wire that joins components together.

Pad: components are placed such that each of their leads is soldered to a pad which is a suitable shape and size to receive them.

Pore? Do you mean Pour?: Imagine you have a large region which you wish to fill with copper. One of the ways to do this is to mark or draw the outline of the region and use the POUR command to let the program fill that region rather than use individual 'lines' of copper.

Via: A means of connecting tracks on each side of the board such that one track is joined to another VIA a through board connection. This usually done with a small pad on each side and a continuous copper connection through the board. Another type of VIA is used sometimes on multilayer boards, it's called a buried via and this means that one or both of the via pads is not visible on a surface board layer.

Assy: This is usually a contraction of the word 'Assembly'

Silkscreen: When populating or stuffing components onto a PCB, life is generally much easier if an image of each component and/or its reference number is printed on the PCB a process known as silk screening.

Finally, Route can be used as a verb meaning join two pads together. It can also allude the to the twists and turns necessary to join a track between two pads.

Hope this helps

Ed

 

[lord loh.]

Thanks a lot....

In case of a multilayered PCB, how many layers can be fabricated?

Does the Via go only to adjecent layers ?

Can there be tracks on layers other than the surfaces ? The ones that are sandwitched ?

I have never seen a multilayered PCB nor do I have any idea of it's fabrication...SO please excuse me if I am asking something foolish.

And thanks for your time for all the explaination.

 

[EdwardM]

Hi Bharath

I've heard of 32 layer boards but personally I've never designed anything greater than 4 layers.

The VIA can span as many layers as required but there is a tendency to have vias go to top and bottom of the PCB in case there is a fault in manufacture.

Yes, there will be tracks on layers other than on the surface as this is this way in which very dense circuits are fabricated, for example if you want lots of copper for current carrying capacity this can be on one or several layers.

To be honest, multilayer fabrication is something of a mystery to me also but if you look at a PC motherboard these are often multilayered but it can be quite difficult to see the difference between them and a normal double sided board

Best of Luck

Ed

 

[EdwardM]

Hi Bharath

just thinking also of those processors which have several hundred pins, imagine trying to get access and connect to densely spaced pins without the ability to have a multilayer board.

Consider also the thickness of each individual copper trace necessary to route between pins, including all the other routes necessary *nightmare*

Ed

 

[Nigel Goodwin]

I have never seen a multilayered PCB nor do I have any idea of it's fabrication...SO please excuse me if I am asking something foolish.

As already suggested, PC motherboards are multi-layer - their manufacture is quite simple?, it's just single or double layer boards stuck together.

The very first Pace digital satellite receivers made (actually for the South African market) suddenly started having huge numbers of failures - which was a total disaster!. It turned out that the manufacturer of the multilayer PCB's used hadn't cleaned the etchant off sufficiently before bonding the boards together. After a few months of use the remaining etchant between the layers started destroying tracks between the different layers :lol:

After LOT'S of very drastic fault finding, the Pace factory managed to find which tracks were the most common failures - and bridged them with external wires - if this didn't cure the receiver, they were scrapped!.