3 ms·
> Larger components will have more surface area at the joint and should be stronger than a smaller component Larger components are also, well, larger, and have
by exmadscientist 3y ago
> Larger components will have more surface area at the joint and should be stronger than a smaller component
Larger components are also, well, larger, and have much bigger forces on them. For ceramic capacitors you need to avoid shearing and torquing as the body of the capacitor is very brittle and a small crack means a dead part, possibly dead short. Big ceramics are dangerous to use as they have a high failure rate. I personally won't use anything larger than a 1210. Some of my colleagues think I'm nuts and should stop at 0805, but I think the flexible terminations available these days make 1210 viable. At least in medium volumes, I don't ship SSDs!
> I can't for the life of me figure out how they came to such a weird conclusion
What I see when I look at this is they have a part with a 5-sided termination (typical MLCC capacitor with metallized cap) but they have a footprint that only gets fillets on 1 of those 5 sides (typical would be 3). This is common for resistors... but resistors (a) have only 3-sided terminations anyway and (b) are made of robust alumina bodies, not fragile ceramics. So someone either got dumb with the footprint library or more likely overly aggressive to pack things in, not appreciating what MLCCs really need to be happy. I don't think it's part size changes, because the fillets along the length dimension that are visible look about right in size.
- mips_r4300i 3y agoMy gut feel was also cracked MLCC ceramics from thermal expansion or shock. I've seen some 1206s shear right off a pcb from merely mechanical shock to the PCB, not the cap directly. When I use them I try to orient them parallel with any PCB bending forces, but they are still fragile.