Electronics Forum | Thu Oct 19 12:34:36 EDT 2000 | lwatson
I can't seem to find an article about the limiting mass of a SMT component on the solderside of a double-sided reflowed PCB. I'm pretty sure that Phil Zarrow did an article on this subject. It went something like the mass/land surface area?
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 | Mon Sep 17 16:03:13 EDT 2001 | jschake
The results from an experiment comparing 27 different combinations of pad dimensions concluded that the pad design with 15 mil pad length, 12 mil pad width, and 9 mil pad separation produced the best assembly yields. A 5 mil thick laser cut stencil
Electronics Forum | Wed Jul 24 17:25:01 EDT 2019 | davef
Your solder stencil design should follow all basic rules for solder stencil design are followed in accordance with IPC-7525 including adherence to an area ratio of 2:3 or greater and an aspect ratio of 1.5 or greater.
Electronics Forum | Mon Oct 15 10:51:49 EDT 2001 | davef
On over printing, the general issues are: * Paste deposits being so large that when reflowing, collapse onto many, rather than a single solder mass. * Paste expanding during heating and being close to other solder deposits and bridging [as you say].
Electronics Forum | Mon Nov 15 12:13:41 EST 1999 | Dave F
Steve: There are guidelines for determining if your aperture has the correct proportions to the foil thickness. Maybe that�s what you�re looking for: 1 Aspect ratio = aperture width/foil thickness Chemically etched SB GT 1.5 Laser cut SB GT 1.2
Electronics Forum | Fri Sep 21 10:56:38 EDT 2001 | davef
Not as such. Look at IPC-7525 �Stencil Design Guidelines� The issues are: area and aspect ratios. They relate the size of the aperture opening to the thickness of the stencil. Check the fine SMTnet Archives for guidelines.
Electronics Forum | Thu Oct 02 17:00:44 EDT 2008 | davef
Is that accurate? If so, what are your aspect & area ratios? [Similar to the JerryS comment above.] * You say, � � and the average height is very high: nearly 200 pct.� => Our troop can make paste that height too. They snap the stencil-off a fast as
Electronics Forum | Thu Oct 02 12:22:26 EDT 2008 | JerryS
Hello Ok there is not much info here. What you have to mae sure of is several key factors. 1. Have you entered the correct stencil thickness. 2. Are you using the stencil gerber (not the paste layer) The paste layer is usually not adjusted for ap
Electronics Forum | Fri Mar 03 14:40:22 EST 2006 | amol_kane
i think a more important issue here would be the reduction ratio. as LF solders have a higher surface tension, they do not flow as well as their leaded counterparts. therefore the stencil design may have to be changed (hence a new stencil) if the red