Regards,My team has completed a design for an Arria 10 SX device, we are using a Flip-chip BGA with 1mm pitch and 0.6mm ball size. According to IPC specifications the landing pad size for a BGA with 0.6mm balls is 0.45mm pads; however it appears Altera recommends a landing pattern with 0.47mm pads and, moreover, the reference design/dev kit Arria 10 SX has pads with size 0.483mm. Any idea why the pad size needs to be larger than IPC recommended guidelines?
IPC recommended 'guidelines' are just that.You can use the ipc-7351b ipc calculator (http://www.ipc.org/contentpage.aspx/contentpage.aspx?pageid=land-pattern-calculator-old) to help determine the IPC recommended landing pad size for a given device geometry. A quick play with the tool, using the detail you posted, results in a recommended landing pad of 0.5mm. Adjusting various parameters within the tool and the answer changes. The very fact that IPC have a tool with the array of parameters on offer shows there isn't a one size fits all. An assembly house is also very likely to comment on any data you send them and request they can, for example, increase pad sizes for reliability of manufacture. You just have to hope they don't wish to increase pad sizes at the expense of nearby features - such as tracks between the BGA pads. Either of the above may well be the case with the Altera reference board you mentioned. Cheers, Alex