Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!zephyr.ens.tek.com!uw-beaver!cornell!rochester!kodak!uupsi!sunic!isgate!krafla!adamd From: adamd@rhi.hi.is (Adam David) Newsgroups: sci.electronics Subject: Re: Surface mount advice wanted Message-ID: <3217@krafla.rhi.hi.is> Date: 31 May 91 12:44:12 GMT References: Organization: University of Iceland Lines: 28 In iisakkil@vipunen.hut.fi (Mika R Iisakkila) writes: >Larger components are impossible to remove with a soldering iron >without ruining the PCB. The only way (that I know of) is to turn the >board upside down and heat the pins of the bloody chip with a hot air >blower until the chip falls off There is another way that works for flat-pack ICs, though not for the PLCC types where the pins are bent under the chip. The only tools required are a watchmaker's screwdriver (really small flat one) and a small soldering iron. This method worked for me using a 15 Watt iron with the usual 45 degree bit. Work on each pin individually, heating the pad and not the pin itself. Wiggle the pin gently side to side with the screwdriver until it moves, remove the heat and keep the pin moving until the solder has cooled. Repeat the process with the rest of the pins, taking care not to heat the pins (pads) which have already been loosened. This takes around 10 to 15 minutes for a 100-pin chip. The screwdriver is made of black iron so the solder doesn't stick to it. The solder melts on each pad long before the board gets damaged by excess heat which would destroy the bonding between the copper and the board. Once three of the four sides are loose, it is possible to lift the chip very slightly on the side farthest from where it is still attached to the board. This makes the last side a little easier because when the last pin has been desoldered the chip just settles under gravity which helps it to seperate from the board. -- Adam David. (adamd@rhi.hi.is)