X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com X-UW-Orig-Sender: fpm AT homer03 DOT u DOT washington DOT edu Date: Thu, 23 Mar 2017 08:13:50 -0700 (PDT) From: "Frank Miles (fpm AT u DOT washington DOT edu) [via geda-user AT delorie DOT com]" To: "John Griessen (john AT ecosensory DOT com) [via geda-user AT delorie DOT com]" Subject: Re: [geda-user] handsolder QFN packages In-Reply-To: Message-ID: References: <20170322172551 DOT DF40C8106DD0 AT turkos DOT aspodata DOT se> <201703221400 DOT 51991 DOT gheskett AT shentel DOT net> <20170322210114 DOT 08D208106DD0 AT turkos DOT aspodata DOT se>

User-Agent: Alpine 2.01 (LRH 1217 2009-02-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-PMX-Version: 6.2.1.2493963, Antispam-Engine: 2.7.2.2107409, Antispam-Data: 2017.3.23.150315 X-PMX-Server: mxout21.s.uw.edu X-Uwash-Spam: Gauge=X, Probability=10%, Report=' TO_IN_SUBJECT 0.5, BLOGSPOT_URI 0.05, HTML_00_01 0.05, HTML_00_10 0.05, KNOWN_FREEWEB_URI 0.05, BODYTEXTP_SIZE_3000_LESS 0, BODY_SIZE_1700_1799 0, BODY_SIZE_2000_LESS 0, BODY_SIZE_5000_LESS 0, BODY_SIZE_7000_LESS 0, DATE_TZ_NA 0, IN_REP_TO 0, LEGITIMATE_SIGNS 0, MSG_THREAD 0, NO_URI_HTTPS 0, REFERENCES 0, SINGLE_URI_IN_BODY 0, URI_ENDS_IN_HTML 0, __ANY_URI 0, __BOUNCE_CHALLENGE_SUBJ 0, __BOUNCE_NDR_SUBJ_EXEMPT 0, __CP_URI_IN_BODY 0, __CT 0, __CT_TEXT_PLAIN 0, __FORWARDED_MSG 0, __FRAUD_BODY_WEBMAIL 0, __FRAUD_WEBMAIL 0, __HAS_FROM 0, __HAS_MSGID 0, __IN_REP_TO 0, __KNOWN_FREEWEB_URI1 0, __MIME_TEXT_ONLY 0, __MIME_TEXT_P 0, __MIME_TEXT_P1 0, __MIME_VERSION 0, __NO_HTML_TAG_RAW 0, __REFERENCES 0, __SANE_MSGID 0, __SINGLE_URI_TEXT 0, __SUBJ_ALPHA_END 0, __SUBJ_ALPHA_NEGATE 0, __TO_IN_SUBJECT 0, __TO_MALFORMED_2 0, __URI_IN_BODY 0, __URI_NO_WWW 0, __URI_NS , __URI_NS_TIMEOUT , __URI_WITH_PATH 0, __USER_AGENT 0' 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 Wed, 22 Mar 2017, John Griessen (john AT ecosensory DOT com) [via geda-user AT delorie DOT com] wrote: > On 03/22/2017 04:15 PM, Erich Heinzle (a1039181 AT gmail DOT com) [via > geda-user AT delorie DOT com] wrote: >> The key features are a ~3mm thick plate to spread the heat, having the >> 800W hot plate starting at ambient remain on for 250 seconds, then >> turned off, then lifting off the board with the jig at about 280 >> seconds, to get a really good fit to the recommended JEDEC heating >> curve. >> >> http://vk5hse.blogspot.com/2011/05/finishing-off-sdr-cube-transceiver.html >> >> being able to lift the board without jostling at 280 seconds avoids >> the problem of thermal inertia of the hot plate continuing to heat the >> board longer than necessary. > > > Thanks, I'm going to try this with my hotplates too. Not sure which one will > give the best thermal > rise-time, so I'll try both. Do you know your hotplate wattage and mass? > One of mine is cast iron top, > one aluminum. Wattage can be important if you're trying to match the manufacturer's temperature cycle ideal. I experimented with varying sheet/plate thicknesses, trying to make the heat as uniform as possible over its surface while keeping the thermal mass low enough that the heater could warm things up quickly enough. Think that was a 0.8 - 1kW heater, which turned out to be kinda marginal (given the weak thermal path from heater -- cast iron top -- top plate -- circuit board). Think I ended up with a ~0.1" thick plate. If the thermal mass of your aluminum top is low enough it would probably be the better choice. While aluminum has a higher specific heat (absorbing more energy) its conductivity is disproportionately greater. -Frank