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PCB Modules - Help in identifying

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chimerahitman:
Hello,

I was looking at Altium's page, http://live.altium.com/#index, and looked at the picture to the upper right which had a board with mini modules on it. I was wondering if it had a proper name I could use to google more info on them.

If no proper name is available, how could I go about creating my own? I am fluent enough in altium, but still can't get my head around the whole pad out of the board. I would like to make the pcb with www.batchpcb.com and see if I can roll out a proof of concept sample.

Thank you,
SRR

Rufus:

--- Quote from: chimerahitman on June 15, 2012, 09:10:40 pm ---I was looking at Altium's page, http://live.altium.com/#index, and looked at the picture to the upper right which had a board with mini modules on it. I was wondering if it had a proper name I could use to google more info on them.

--- End quote ---

They are PCB modules with what is called castellated surface mount pads (or possibly holes).

As far as Altium is concerned they are called 'our next fail'.

Zad:
That has the smell of Marketing Department all over it :(

free_electron:
Indeed boards with castellated contacts.
i have design rules to make this. Batchpcb or iteadstudio cannot handle this. it requires additional steps in the pcb process that they don't have.

Essentially the castellation contact area is milled first together with the drill holes in the board.
Then the board is subjected to a selective plating using electroless copper to create the edge contacts. Then the board is milled again to remove the copper deposits where no copper should be. After that pcb follows classic electroplating so copper grows only on the contact area that was left after milling. At the end of the production run the isolation fingers are milled off. This requires tight tolerances on the countour milling.

The sloppy way is to simply specify a large via or pad and mill it in half. The problem is this creates burrs and may rip the metallisation off the hole wall. And the edge of the board will not have vertical plating either.

a cleaner way is to simply draw a square pad top and bottom and connect it vertically. You then treat the board as a QFN of MLF style package but you have no true edge plating.

Real castellated boards require process technology and steps that are not in amateur domain. i have done castellation board to convert a BGA to TQFP package. The castellated board had fingers that look like TQFP pins. You would solder this little board on a TQFP64 footprint and it would carry the BGA on its back.
Board thickness was 8 mils ( not the usual 62 ) 4 layer and used plugged and blind via's ( via in pad. the via is squirted shut after first plating using a conductive epoxy and then another plating step grow copper over the plugged hole as well so you see no holes in this board... )

you will need to talk to the boardfab you will use to ask them the milling width and edge pullback numbers. Sierra can mill with a 20 mils router bit and the pullback can be 8 mils.

hang on i'm taking a picture

( and don't listen to the doomsayers bashing altium. they are just jaleaous they have to muck about with counterintuitive, counterproductive, stone-age tools and can't afford something like Altium)

here you go : This is the TQFP to BGA ( actually a bga with a thermal slug in the middle and long outside fingers for high current. the real name is a VQFN-MR package ) board.

Made by Sierra Proto Express.

chimerahitman:
free_electron:

WOW! Thanks for such an informative explanation.

It is a bummer that it cannot be achieved with cheap PCB manufacturers. Oh well, I will consider your simple solution with pads used as a QFN style package, if not, I will go with boards with headers near the edges. Last option will give me the possibility of placing components on the bottom layer.

Would have been a great way of build up systems with already tested modules to speed up designs.

Thank you, free_electron!!!

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