Electronics Forum | Tue Feb 11 10:51:20 EST 2020 | slthomas
To predict whether or not a first pass part is going to come off during the second pass you need to calculate the ratio of weight/soldered surface area. According to a couple of different sources that I've dug up, maximum is around 44 grams/in.^2. I
Electronics Forum | Thu Mar 04 12:49:49 EST 1999 | SMTASSY
| Are square pads more difficult to wavesolder than round pads? | I am referring to a through hole board. | Usualy square pads are for indication of pin 1 on a DIP for example. There might be a difference in the capilary affect due to a different su
Electronics Forum | Tue Mar 21 02:15:26 EST 2006 | pavel_murtishev
Good morning Dave, Here are some of my assumptions. Please correct me if I am wrong. 1. Mask opening. Due to mask to PCB misregistration mask is not always centered relative to pad center how is should be. Sometimes edge of the mask matches with ed
Electronics Forum | Sat Apr 17 12:00:12 EDT 1999 | John W
| | | | Can someone explain the difference between solder "fines" and solder balls? Is there an official specification where "fines" are defined? What is the spec for "fines"? | | | | | | | | I consider "fines" individual unmelted metal spheres t
Electronics Forum | Sun Apr 18 00:26:29 EDT 1999 | Vic Lau
| | | | | Can someone explain the difference between solder "fines" and solder balls? Is there an official specification where "fines" are defined? What is the spec for "fines"? | | | | | | | | | | I consider "fines" individual unmelted metal sph
Electronics Forum | Tue Mar 28 08:29:04 EST 2006 | davef
Pad design - Standard IPC 20 pitch QFP Thermal pad design - Layout the thermal pad 0mm to 0.15mm larger per side (0mm to 0.30mm larger overall) than the exposed die pad on the package. �Larger than�, as opposed to the same size, is preferred. Obvio
Electronics Forum | Mon Jun 07 21:31:46 EDT 2004 | davef
That's thin board. The test that you ran is the best method for determining the specific answer. Bob Willis says, "Use pad mating to lead wetting area. Some have found the ratio to be as much as 44 grams/sq in." Bob Willis and Phil Zarrow have po
Electronics Forum | Mon Aug 09 08:16:44 EDT 2010 | markhoch
It will most likely hold on. There is a formula that you can use if you're uncertain. It's (weight of the component in grams)/(total pad mating area in square inches) Grams per square inch must be less than or equal to 35 for the component to be mo
Electronics Forum | Tue Dec 05 03:39:39 EST 2006 | pavel_murtishev
Good afternoon, Due to problems with power connector soldering I have to overprint paste on pads for this connector. Stencil thickness is 125um and I cannot make it thicker. Area ratio of chip resistor assemblies limits stencil thickness to 125um. R
Electronics Forum | Fri Jul 13 19:35:02 EDT 2007 | hegemon
We have had good success doing pb Free QFN work. Typically for the center pad we use ~68% coverage with 1:1 ratio on the perimeter pad. For the 68% coverage we have tried cross hatch pattern, diagonal stripes, dot series, and most successfully a clo
