Hi Bill,
Good friends mate. Share a beer with you anytime. Any other designer too,
for that matter. Let's meet for a beer half way - say around Hawaii <grin>
The 0.2mm solder mask opening comes from a pitch of 400um, leave 100um gap
between copper pads, then you have +/- 50um solder mask registration
tolerance. That only leaves 200um soldering surface.
You could pay heaps more for better solder mask registration and get the
pads to a more desireable 250um opening, but I'm not sure you (or your
customer/company) would want to do that.
Cheers........
AndyK
0424 432 235
On 25 March 2017 at 06:39, Brooks, William <
[log in to unmask]> wrote:
>
>
> So true Andy… the excitement never ends… lol J Thanks for your insights
> again… you have always been a good friend…
>
> We need to get together and have a beer again. J
>
>
>
> 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 <+1%20760-930-7212>
>
> CEL: +1.760.216.0170 <+1%20760-216-0170>
>
> [log in to unmask]
>
>
>
> *From:* Andy Kowalewski [mailto:[log in to unmask] <[log in to unmask]>]
> *Sent:* Thursday, March 23, 2017 1:17 PM
> *To:* (Designers Council Forum) <[log in to unmask]>; Brooks,
> William <[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 <william.brooks@
> nordsonasymtek.com> 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
> CEL: +1.760.216.0170
> [log in to unmask]
>
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