The PCB doesn't need solder, as you say, the balls ARE solder. *I just "broke" a template, so I manually placed 100+ 0.5mm balls on a chip using a pin and a microscope.. it CAN be done, but it SHOULDN'T be done! -Jim -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Electron Sent: 16 October 2011 16:45 To: Microcontroller discussion list - Public. Subject: Re: [EE] Soldering BGA At 01.56 2011.10.15, you wrote: >V G wrote: >> So it seems that I have to use this >>=20 >BGAs= /dr am/psram-cellularram/MT45W8MW16BGX-701+IT>part >> (can't find it in any other package). How would I go about soldering >> it? Just place it on the PCB and stick it in the oven? My biggest concer= n is >> the positioning of the part on the pads. How would I know that it's aligned >> properly? How perfect does the aligning have to be? >> =20 >Afaict the aligning doesn't have to be perfect, the surface tension of=20 >the balls will snap it into place if it's slightly off. The problem=20 >comes if it's sufficiantly far off that it snaps to a 1 ball offset=20 >rather than snapping to the correct position or if it decides to solder=20 >itself to the vias instead of the pads (see below). > >If there is going to be a grid of vias under the BGA connected to the=20 >grid of pads via 45 degree tracks it is strongly advisable to set up=20 >your PCB package to cover the vias in soldermask. Another option is to=20 >put the vias in the pads themselves but if you do this then those vias=20 >need to be filled with solid copper which will increase your PCB=20 >fabrication cost (given how fine this BGA is though you may have little=20 >choice but to go for vias in pads). By the way do BGA's require solder on the PCB pads? If I'm not mistaken those BGA balls are already exactly that: solder. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .