Electronics Forum | Sun Dec 08 22:20:39 EST 2002 | grantp
Hi, We have been manufacturing a PCB, however it's been quite tricky to profile, as the edges of the PCB are reflowing before the center of the PCB. I have looked at the design, and there is a small power plane for 2.5 Volt in the center of the PCB
Electronics Forum | Mon Dec 16 10:05:29 EST 2002 | Grant Petty
Hi, Thanks for the info. We are reflowing the boards, but just barely. Sometimes we get the QFP in the middle of the copper area not reflowing, and it's pain. The joints are dry, and I am not sure if it's caused by lack of heat, or the flux going ba
Electronics Forum | Mon Dec 16 10:31:21 EST 2002 | davef
Grant, On those 'dry pads', where does the solder paste end-up after soldering? On: * Pads * Component leads * Someplace else [Where?]
Electronics Forum | Mon Dec 16 21:51:28 EST 2002 | grantp
Hi, It's on the pads. They look ok, but when you check the lead comes away from the solder. Regards, Grant Blackmagic Design
Electronics Forum | Tue Dec 17 18:37:18 EST 2002 | davef
As a starting point, consider that these component leads may not be getting hot enough. Measure the temperature profile on the leads that do not solder well to be sure: * Heating and cooling ramps are within the paste supplier's recommendations. * C
Electronics Forum | Mon Dec 09 08:13:06 EST 2002 | MA/NY DDave
Hi Yes it is common to design for more uniform heat transfer during the soldering phase or even during the operation phase. It all depends on how bad the problem is during automated assembly or during usage. The only difficulty is that the designer
Electronics Forum | Tue Dec 17 08:55:52 EST 2002 | Randy Villeneuve
Grant, The board maybe the problem but how is your oven working? Is it a convection oven and how many zones (top and bottom)? What does your profile look like? If you are unsure and if you only have one oven, send your board to Soltec or Electrovert
Electronics Forum | Mon Dec 09 09:31:35 EST 2002 | MA/NY DDave
Hi Just one idea, many exist. If your electrical designers can tolerate it, sometimes a cross hatched design is used under areas where electrical performance is important. It reduces coupling and impedance effects compared to a full layer. Elimina
Electronics Forum | Mon Dec 09 09:54:16 EST 2002 | davef
Large copper pours create an unbalanced lay-up that is bad design practice, creating problems in fabrication and assembly. The hatching a previous poster mentioned could be an alternative. Stepping back a bit and wondering, what's the problem? You
Electronics Forum | Mon Dec 09 20:34:20 EST 2002 | MA/NY DDave
Hi I hear you, and you are right, yet most good process engineers strive to make future life a little easier by going back to the designers and making some alterations that don't affect performance. Now if we did a 6 sigma type analysis than this p
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