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Sockets Impedance. Signal Integrity

joser , 10-09-2015, 01:36 AM
I'm considering split the design into two boards, one we could call mother board and other little board witch could have 3/4 variations, Like for example your design of iMX6, you have a motherboard and on the other hand you have a module witch you can fit in the first one. I'm thinking about doing the same thing in my project but i'm considering not using any kind of socket to join the two boards, simply doing pads in the bottom side of the module and soldering in the fabrication process, because once the module take place i dont need to take off again. I dont know if you have any experience with this sort of situation. So the question is, is there any problem with the impedance continuity, in the pad where de conection beetwen the module and the base board take place, its form some sort of stub (signals frequency is about 100Mhz), And also the connectors you use to do the connection in your design iMX6, you use especial connector witch you actualy are aware about the impedance or maybe it doesn't care. I wonder if you know any way of simulating signal integrity in this situation with no ibis model.
robertferanec , 10-09-2015, 04:57 AM
It may depend on the interfaces and price of the module. I have seen pads used on slow interfaces e.g. UART and I have done it once on SDIO. What interfaces are you trying to connect?

For two board simulation (e.g. in Hyperlynx) you normally need to add some parameters of the "connector" as resistance, inductance, capacitance, impedance and delay .

BTW, some board to board connectors are not expensive. The one we used on TinyRex cost around 1USD / 1000pcs: DF40C-100DP-0.4V(51), but with less pins you can buy them from 0.5USD/1pcs e.g. DF40C-10DS-0.4V(51)
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