To effectively use the IPC 7351.pdf standard, designers and manufacturers should follow these steps:
| Revision | Year | Key Change | |----------|------|-------------| | IPC-SM-782 | 1987 | Original surface mount standard. | | IPC-7351 | 2005 | Introduced three-density concept; deprecated SM-782. | | IPC-7351A | 2008 | Minor corrections, added QFN/BGA data. | | IPC-7351B | 2010 | Added land pattern calculators and tolerance tables. | | | Current | Updated for ultra-fine pitch (0.3 mm), leadless components, and solder joint reliability modeling. | IPC 7351.pdf
If you are using this standard for a new design: To effectively use the IPC 7351
If the thermal mass of two pads is unequal or the pad lengths are too short, one side of a resistor reflows before the other, causing the component to stand upright. IPC-7351’s minimum heel and toe extensions prevent this. | | IPC-7351B | 2010 | Added land