Multilayer Ceramic Capacitors under chipsets??

[stevo1210]

Hello Everyone,

I'm starting to notice something on certain motherboards. Why is it only motherboards that use VIA and SiS chipsets have Multilayer ceramic caps on the other side of the motherboard PCB.... odd thing is that they are directly underneath the Northbridge and southbridge.
I have never ever seen an Intel Chipset motherboard with MLCCs on the other side of the chipsets.
I have no idea about nvidia chipsets, but i'd really like to know if there are MLCCs on the other side of nvidia chipsets.... I'm planning to buy an nvidia nforce 4 chipset based motherboard and I want to know if they have MLCCs on the other side of them??
Why do those chipsets need MLCCs on the other side??
Multilayer Ceramic caps are a real pain for me because they can sometimes break off if I accidentally put the board against a table and slide it over etc. Then i have to solder them back on which is an even harder job.

Thanks.

[japlytic]

Re: Multilayer Ceramic Capacitors under chipsets??

The reason why the MLCCs are directly under the chipset is because of the close proximity required between the chip supply and ground pins for good transient suppression with MLCCs, especially with BGA packages or if other components are taking up the space around the package.

[linuxguru]

Re: Multilayer Ceramic Capacitors under chipsets??

1) Intel probably has got well-designed Si in its Northbridges and Southbridges, probably with careful slew-rate control on all I/O buffers that allows them to keep Vcc transients under control even with the MLCCs located some distance away.

2) Intel chipsets probably find their way into higher-end boards which are likely to use 6-layer PCBs including at least 2 power planes. That will offer some high-frequency transient suppression due to the distributed capacitance of the power planes. It's likely that most SiS and Via chipsets find their way into lower-end 4-layer boards.

[stevo1210]

Re: Multilayer Ceramic Capacitors under chipsets??

What about nvidia chipsets?? do they also have MLCCs on the opposite side of the chipset??

[linuxguru]

Re: Multilayer Ceramic Capacitors under chipsets??

A quick look at an old MS-6777 Nforce2 motherboard reveals that it has MLCCs below both the NB and SB BGA packages. BTW, that board has eaten up a couple of Thoroughbreds, but there's nothing visibly wrong with it - looks brand new.