So true Andy… the excitement never ends… lol ☺ Thanks for your insights again… you have always been a good friend…
We need to get together and have a beer again. ☺
So it sounds like the solder mask defined pad approach is the way to go…
1) If the column or pillar is .2mm dia. then the pad should also be defined at the same size?
2) Is there any reference info on the soldering of these that you are aware of??
In this case we are going to under fill the chips after assembly… with epoxy.
Should be interesting…
William Brooks, CID+
Printed Circuit Designer
Nordson Asymtek
2747 Loker Avenue West
Carlsbad, California 92010-6603 USA
TEL: +1.760.930.7212
CEL: +1.760.216.0170
[log in to unmask]<mailto:[log in to unmask]>
From: Andy Kowalewski [mailto:[log in to unmask]]
Sent: Thursday, March 23, 2017 1:17 PM
To: (Designers Council Forum) <[log in to unmask]<mailto:[log in to unmask]>>; Brooks, William <[log in to unmask]<mailto:[log in to unmask]>>
Subject: Re: [DC] soldermask clearance around BGA balls
Hi Bill,
You're in a swamp at that pitch.Couple of things:
1) Your assembly people need to talk to you. Paste deposition will be a big issue.
2) You won't be able to use a mask because of the 0.1mm (4mil) web thickness needed, unless you
3) Use Mask Defined Pads. These can be copper 0.3mm diameter with a 0.2mm dia opening. That will give you consistent copper area for soldering too.
4) Mask defined pads on a BGA were considered a no-definitely-not strategy, but some studies we did years ago proved that the tendency for balls to crack at the mask edge and spread from there went away if the mask was very thin. We used LPI no greater than 10um thick on the copper and never had a problem. That was on small modules with even finer pitch that 0.4mm
Go for it - the excitement to design where you've not gone before doesn't get any less as we get older. Right?
Cheers........
AndyK
0424 432 235
On 24 March 2017 at 06:58, Brooks, William <[log in to unmask]<mailto:[log in to unmask]>> wrote:
I'm playing with some small featured chips and want to create a footprint for a .4mm pitch chip with 64 copper pillars rather than solder balls.
I can't find a recommendation for the land pattern... not one that makes sense anyway... :)
How would you approach creating a producible, useful, land pattern for this type of chip?
What clearance would you use for the soldermask around the copper pillars and their lands...
I'm using lead free solder... SAC305.
Thanks in advance for any advice you may have... :)
http://www.topline.tv/drawings/pdf/eWLP/eWLP64T.4-DC088D.pdf
William Brooks, CID+
Printed Circuit Designer
Nordson Asymtek
2747 Loker Avenue West
Carlsbad, California 92010-6603 USA
TEL: +1.760.930.7212<tel:%2B1.760.930.7212>
CEL: +1.760.216.0170<tel:%2B1.760.216.0170>
[log in to unmask]<mailto:[log in to unmask]>
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