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I need to design a modular circuit and I was thinking about making smaller identical pcbs and solder them on a bigger board (also for module reusability, hyerarchical and modular assembly). The first approach I was thinking is the castellation but I saw that it is a non-standard design option for most pcb manufacturers. Is it possible to use the second side of the pcb (unpopulated) to attach the same balls of a BGA package? What are the drawbacks? It should also use less space on the bigger board than castellation pads.

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  • \$\begingroup\$ Imagine what happens to your module when someone tries to solder it on \$\endgroup\$ – PlasmaHH Oct 14 '16 at 8:12
  • \$\begingroup\$ You are right. It would require a high temperature material. Castellation would be cheaper. Thanks! \$\endgroup\$ – KBowser Oct 14 '16 at 8:16
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    \$\begingroup\$ @Botnic: thats called castellation and I have the feeling he already knew abou that \$\endgroup\$ – PlasmaHH Oct 14 '16 at 8:18
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    \$\begingroup\$ @dim: It needs careful planning to make a module that can be reflowed that way. Unlike the castellation one, you would need a much heftier reflow profile to get things done properly. You would need parts that can withstand that profile. You need the right thickness for the module to not bend and cause passives to tombstone upon their second reflow. There are many things to consider, thus imagining what exactly happens with the module when someone tries to solder it is the first step to think about if it has a high probability to survive it \$\endgroup\$ – PlasmaHH Oct 14 '16 at 9:03
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    \$\begingroup\$ @Botnic: There are plenty of BGAs that are WLCSP attached to a small PCB or CoB. Take a look at many microcomputer CPUs and chipsets. \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 14 '16 at 9:48

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