Author Topic: PCB design for multiply packaged versions of same component.  (Read 2484 times)

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Offline abaxas

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Lets say you wanted to do a layout that accommodated both SMT and through hole versions of the same component, how would you do this?

Eg. 741 opamp  is available in



and...



Hence I would want to design a board so you could use both the SOIC and DIP versions. How would people approach this?

I'm using eagle so I guess I could just double up everything in the schematic. But there must be a more elegant or standard way as it's not exactly uncommon to find this out in the wilds.

 

Offline sacherjj

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Re: PCB design for multiply packaged versions of same component.
« Reply #1 on: May 05, 2014, 11:01:37 am »
If the SMT footprint will fit inside the TH footprint by enough to offer solder mask, then you can just put it in the middle.  This may be a situation where a much smaller SMT footprint is helpful.

The problem you will run into is if the copper for TH and SMT touch.  That is inviting solder to get sucked down the rabbit hole and leave your SMT component with no solder.

I would probably make a footprint that is two in one, with it shifted to the side.

Something like this with 'O' being a TH pad and [] being an SMT pad.
Code: [Select]
O--[]   O--[]
O--[]   O--[]
O--[]   O--[]
O--[]   O--[]

You could look at the TH pads as free big vias for routing the SMT part, I guess.
 

Offline Mechatrommer

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Re: PCB design for multiply packaged versions of same component.
« Reply #2 on: May 05, 2014, 11:26:14 am »
or like this if it fits
Code: [Select]
O--[]   []--O
O--[]   []--O
O--[]   []--O
O--[]   []--O
i've seen its commonly done for TQFP of various chip sizes in breakout or test board sold in ebay or something. but it will limit your capability to route under and between pins of the TH. btw i wonder if its common for other "mainstream" softwares like altium or cadence to make a single component with multiple footprints combination (with the schematic component) capability. decision to change ic package later (after circuit design or pcb layout) is as simple as selecting another fp in the component setting without the need to this overlapping TH/SMD hack. need to check this one out.
It's extremely difficult to start life.. one features of nature.. physical laws are mathematical theory of great beauty... You may wonder Why? our knowledge shows that nature is so constructed. We simply have to accept it. One could describe the situation by saying that... (Paul Dirac)
 

Offline sacherjj

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Re: PCB design for multiply packaged versions of same component.
« Reply #3 on: May 06, 2014, 01:06:37 am »
or like this if it fits
Code: [Select]
O--[]   []--O
O--[]   []--O
O--[]   []--O
O--[]   []--O

Yep, that is exactly what I would think for SMT fitting inside.

Quote
btw i wonder if its common for other "mainstream" softwares like altium or cadence to make a single component with multiple footprints combination (with the schematic component) capability.

Can't speak for Cadence, but in Altium you define a schematic.  Then you associate 1 or more footprints.  You can pick the footprint at any time and change it after you routed the PCB (just have to fix up the differences).
 

Offline scientist

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Re: PCB design for multiply packaged versions of same component.
« Reply #4 on: May 08, 2014, 03:36:47 pm »
KiCad can do this. Just select different footprints in Cvpcb.
 


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