www.megadrum.info

Hi Guys,
I'm a bit of a newbie to this, and struggling a bit with the SOIC adapter idea!...I've got hold of some extremely small SN74HC4851D MUX/DEMUX chips to go onto a V2.5 board. What I can't work out is how to fit them, do I make up a seperate adapter board, and if so do I fit this to the copper or base side of the mainboard. I've downloaded the pcb design for the adapter and it doesl look like the pins on my chips don't line up with the pcb ones. I know these may seem like stupid questions, but please bear with me.
Pilot40

pilot40 wrote:What I can't work out is how to fit them, do I make up a seperate adapter board, and if so do I fit this to the copper or base side of the mainboard.

The adapter must emulate a DIP packaging and so should be soldered on the same side as a DIP IC.

I've downloaded the pcb design for the adapter and it doesl look like the pins on my chips don't line up with the pcb ones.

Then it is a wrong adapter.

Get the pin pitch from the datasheet and use something like
http://parts.digikey.com/1/parts/298569-socket-adptr-soic-16pin-300dip-16-350000-10.html
or
http://www.sparkfun.com/commerce/product_info.php?products_id=498

Or if you are going to spend six dollars on an adapter, just order the correct IC.

He's got the correct ICs, maybe he wants a different board?!

I guess I'm not following the problem. I thought he had a different component package and was trying to adapt it to fit the v2.5 board?

pilot40, where are you downloading the adapter board from?

It's the Synthex CMS to DIP adapter in one of the forum posts, the IC's are also described as being suitable, I got them from Farnell, using the link from MegaDrum. I might just be stupid or something, but I can't see how the pins on the chips (they are extremely small) are going to line up with the 'pads' on the adapter. This might seem like a bizzare idea, but isn't it possible to 'edit' the existing V2.5 PCB design and 'overlay' the design from the Adapter PCB making the 'pad' sizes slightly larger. Also if I do use the adapter, would it be best to 'stand' it off the face of the main PCB with strip headers?
Thanks for any help.....I'm getting frustrated with this now!

OK, just re-scaled my printer slightly, and managed to get everything to fit, it's going to be a bit tight with old soldering though !!

Glad you got it. There are some programs out there that will turn a pdf into a jpeg and then you can edit it to your hearts content. You just have to be sure to retain its original size. I have done it several times.