Author Topic: LGA solder pad size  (Read 3012 times)

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Offline danbr

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LGA solder pad size
« on: April 28, 2015, 02:01:12 pm »
Hey,

I'm trying to build up a part in eagle cad using the LPS25H pressure sensor.

The problem I'm having is that the datasheet for the part has a HORRIBLE diagram for trying to figure out the LGA solder pad size and placement. Its a HCLGA-10L package.

Page 43:
http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/DM00066332.pdf

Is there something I'm missing here? Or does the diagram really suck. This is pretty much the only thing keeping me from going to the pcb printer.
 
 

Offline chibiace

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Re: LGA solder pad size
« Reply #1 on: April 28, 2015, 02:16:43 pm »
its not too bad, annoying not to have the numbers right there on the measurements though.
He Who Controls The Spice Controls The Universe
 

Offline danbr

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Re: LGA solder pad size
« Reply #2 on: April 28, 2015, 02:23:37 pm »
The dimensions for placing the pads isn't so bad.

But I'm I missing something, no where do I see the length and width of the pad listed. I know my geometry, and assuming that image is to scale I could figure it out, but that seems like a pain for what should be a simple listed dimension.
 

Offline chibiace

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Re: LGA solder pad size
« Reply #3 on: April 28, 2015, 02:47:09 pm »
b: 0.25 0.35
He Who Controls The Spice Controls The Universe
 

Offline danbr

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Re: LGA solder pad size
« Reply #4 on: April 28, 2015, 02:59:15 pm »
What the hell?!

B = b?

Why couldnt they just use matching notataion  |O
 

Offline T3sl4co1l

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Re: LGA solder pad size
« Reply #5 on: April 28, 2015, 05:55:08 pm »
Yep... have fun with that...

You'd think it was drawn in China......maybe it was..

Seems like they're missing a full page: detail "B" is missing; notes 3, 4 and 6 are indicated but missing (no idea about the remaining notes); section A-A is missing; and dimensions b and L are missing from the drawing (likely belonging to detail "B").

b and L are IPC standard symbols for width and length of the pad, in any case, so that should be what you need.  Mind that pads 1, 2, 6 and 7 are rotated.

IPC rules are usually pad = pad (nominal zero side fillet), with NSMD (non soldermask defined) preferred.

The product page, http://www.st.com/web/en/catalog/sense_power/FM89/SC1316/PF255230?s_searchtype=keyword# suggests this (Design Resources / TN1198), but sadly doesn't provide the missing drawing sheet!

You can email them about it.  You might get a response, which is nice; but in my limited experience with ST, you won't get action.

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline danbr

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Re: LGA solder pad size
« Reply #6 on: April 30, 2015, 01:43:17 pm »
I contacted ST support and they did get back to me!

They suggested that I use the LPS25HB, as both the documentation is better (for dimensional drawings) as well as its a waterproof sensor! The electronics are the same I was told, so I will just go with this new part.
 

Offline michael.hill

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Re: LGA solder pad size
« Reply #7 on: April 30, 2015, 05:37:58 pm »
I'll never understand why component manufacturers don't utilize reference dimensions...The rest of the world has learned to use them.
 


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