Sorry guys have a look at this list of component weights and then work out the surface area of the lead/pad and then come back on the PLCC issue. Chip 0805���� 0.007g������ 2 Chip 1206���� 0.009g���� 2 Chip 1210���� 0.012g���� 2 SOT23���������0.008g���� 3 SOT89���������0.0976g���� 4 V/Resistor���� 0.124g���� 3 MELF�����������0.1325g���� 2 Mini MELF���� 0.031g�������� 2 SOIC8����������0.102g 8 SOIC12�������� 0.123g 12 SOIC16�������� 0.142g 16 TSOP20�������� 0.212g 20 PLCC28�������� 0.688g 28 PLCC44�������� 2.21g 44 PLCC68�������� 4.67g 68 PLCC100�������� 9.97g 100 LCCC44�������� 5.32g 44 PLCC84�������� 5.21g 84 PLCC100�������� 9.97g 100 QFP100�������� 4.24g 100 BGA225�������� 2.65g 225 BGA313�������� 6.32g 313 CBGA256�������� 24.21g 256 CCGA625�������� 29.53g 625 CCGA1089����� 34.12g 1089 Tape BGA360���� 2.695g 360 The formula that most people use is conservitive. The real problem for double sided reflow is board sag and vibration. If you want a copy of the Double Sided Reflow Desing and Assembly report contact the main USA SMTA office. The proceeds from the sale of the report is going to a USA charity.
| Stoney, | One thing you might do before you start dispensing epoxy, (...I know this might be a bit of a pain) is to run your boards on the mesh belt instead of the edge-rail conveyer. I used to have to do that with some very,very dense double sided memory modules due to the sheer weight of all the DRAM. If I got the profile hot enough to reflow, I'd be bowing my boards and parts would start dropping, if I cooled it up a bit to keep from bowing, I'd have cold solder...so I just ran em' on the mesh belt. Make sure your mesh belt is traveling smoothly and there ain't no "whoop-dee-do's" through-out the boards travel thru the oven...(make sure your belt is, and stays, nice and flat) | -Steve Gregory-
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