Electronics Forum | Mon Jun 25 20:37:14 EDT 2001 | davef
You are 100% correctamundo that the pad on PCB should be the same as the pad on the BGA interposer, but let�s not expend that thinking to the aperture of your solder paste stencil, right away. Generally, paste on large pitch BGA is often 1:1, but as
Electronics Forum | Mon Aug 13 12:38:38 EDT 2012 | grahamcooper22
Maybe the area ratio between the sides of the stencil apertures and the aperture opening is too low for the spec of the paste ? So it will tend to stick in the apertures. ...only solution is thinner stencil or a paste that can release easily when are
Electronics Forum | Wed Jul 10 14:25:04 EDT 2013 | pankajp
thanks ben. any ball park number for weight of solder paste per pad? ( i understand this will be dependent on AREA of pad, but a rough estimate is good enough for me). -Pankaj
Electronics Forum | Mon Aug 19 20:45:31 EDT 2002 | davef
Bob Willis and Phil Zarrow have had a running commentary on the ability of reflowed solder to hold components on the bottom side during reflow. You can find references to their component weight to pad area rations in the fine SMTnet Archives. The
Electronics Forum | Fri Jan 10 03:57:37 EST 2020 | jakapratama
Hello, When I calculate based on the data you gave, your stencil aperture area compared to pad area is 94.52%. Your aperture area ratio is 1.76 using 5 mils thickness foil. OK, your stencil and your paste release is not the culprit here. Your proble
Electronics Forum | Wed Jun 14 12:43:52 EDT 2000 | Todd Murphy
Dave, you are right you would expect the soldermask to be higher than all SMT pads on the pcb if it is higher on the fine pitch components, but the other areas of the board do not concern me as much as the fine pitch areas. The pads on all the other
Electronics Forum | Tue Sep 16 13:40:20 EDT 2008 | ck_the_flip
Try reductions in the "Y direction". For the SMALL PAD, go from 16-mils to 14-mils, and on the large pad, you can play around with reductions on the 14x24mil pad...or try mesh pattern. You'll be well with area-ratio guidelines with both approaches,
Electronics Forum | Tue May 26 15:39:16 EDT 2009 | mikesewell
Amkor's MLF guidelines are very similar to Actels. 1 to 1 on the stencil to part pad on the I/O pads, 75% with a grid windowpane, 0.125 mm/5 mil stencil. For example, the Actel area ratio for a 0.3 mm sq. pad and 0.125 mm stencil is 0.6 which seems
Electronics Forum | Thu Jun 16 18:19:05 EDT 2005 | Jason Fullerton
If the uBGA has aperatures that are 0.25mm square, you need to use a laser cut foil no thicker than 3.75 mils to get an area ratio of 0.67, which is the minimum rule of thumb - that's too thin! Electroform would probably work up to 4.5 mils thick.
Electronics Forum | Mon Mar 09 11:43:59 EDT 2009 | pcbrown
Here is a formula that may help. C/P C= Component's weight in grams P= Total pad area in Sq. in. Must be less than or equal to 30 Parts larger than a 68 pin PLCC should use an adhesive. Hope this helps.
