X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com Date: Fri, 22 Mar 2019 10:05:59 +0100 From: "Gabriel Paubert (paubert AT iram DOT es) [via geda-user AT delorie DOT com]" To: "Richard Rasker (rasker AT linetec DOT nl) [via geda-user AT delorie DOT com]" Subject: Re: [geda-user] Modify SMD stencil aperture size to prevent short circuits? Message-ID: <20190322090559.op775lcm6jc5ksnd@lt-gp.iram.es> References: <999a6a2b-c727-4f22-3aaf-b6c20cf15807 AT linetec DOT nl> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <999a6a2b-c727-4f22-3aaf-b6c20cf15807@linetec.nl> User-Agent: NeoMutt/20170113 (1.7.2) X-MIME-Autoconverted: from 8bit to quoted-printable by mx01.puc.rediris.es id x2M969xN031855-x2M969xP031855 Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id x2M96Chh022405 Reply-To: geda-user AT delorie DOT com Errors-To: nobody AT delorie DOT com X-Mailing-List: geda-user AT delorie DOT com X-Unsubscribes-To: listserv AT delorie DOT com Precedence: bulk On Thu, Mar 21, 2019 at 12:01:44PM +0100, Richard Rasker (rasker AT linetec DOT nl) [via geda-user AT delorie DOT com] wrote: > After some searching, I found that decreasing the size of the openings in > the stencil and thus the amount of solder paste ending up on the PCB appears > to be a common way to prevent shorts of this nature. Indeed, that's one of the reason which pushed me to switch to pcb-rnd. When I still used pcb, I wrote awk scripts that edited the pcb file and produced a temporary one which was exclusively used to generate the solder paste stencils. However, the pads were still centered, for 0402 and especially 0201, I've found that slightly off-centering the paste towards the outside improves the result. > > Can anyone confirm that this is indeed a good idea? It would probably mean > that I'd need to make two copies of each layout: one with the desired PCB > pad sizes, and one with reduced pad (and thus aperture) sizes for stencil > production. And what reduction percentage would be recommended? At several > dozen dollars plus at least a week delivery time per stencil, I don't want > to mess around too much with trial-and-error. For 0.5mm pitch (~0.3mm wide pads), I reduce the stencil aperture by 50µm. That's with 125µm thick steel stencils. Regards, Gabriel