Bead Probe Technology-Alternatives-circuit
Board Electronic Pcb Assembly
Boundary scan integrates test components into the integrated circuits (ICs) mounted on the board, giving the ability to read or drive the ICs' pins. This allows for testing of interconnects for which physical access is not an option, such as BGA components or signal routes sandwiched between plane layers. A boundary scan controller uses four or more dedicated pins on the board to control test cells serially and receive the measured values. It has the disadvantage of needing board infrastructure to support boundary scan.
Test Access Component (TAC) uses a device such as a 0201 as a target for a large probe as in the solder bump examples. The advantage of this technique is that it provides two target points at each end of the package. The disadvantage of this technique is it can add process and cost to the PCB.
A technique has been described which opens up windows in the solder mask to create test points located directly on PCB tracks. This technique uses a conductive rubber tipped probe to contact the test point which could have a conductive Hot Air Solder Levelling (HASL) finish.