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74 SMT007 MAGAZINE I OCTOBER 2026 An interposer is a thin substrate posi- tioned between a semiconductor device, such as a BGA and PCBA. It contains conductive features that allow electrical connections to be rerouted, recreated, or modified between the component and the PCB. Interposers may be manufactured from organic materials such as polyimide or FR-4, as well as silicon, glass, or other specialized materials. In PCB rework, they are most commonly used when the existing board design cannot easily be modified through conventional rework techniques. Advantages and Limitations Interposers can provide several important benefits: BY N AS H B E L L , B EST, I N C. Interposer Rework and Precision Solder Ball Attachment K N O C K I N G D OW N T H E B O N E P I L E • Allows an existing PCBA to be modified or up- graded without a full board redesign • Eliminates the need to replace an expensive multilayer PCB in certain applications • Permits connections to be rerouted when pads, traces, or internal connections are dam- aged or inaccessible • Supports engineering change orders or com- ponent substitutions without requiring a new PCB revision • Provides a practical option for prototype de- velopment and low-volume modifications The tradeoff is additional complexity. An interposer Figure 1: Typical BGA mounted to an interposer above the PCB.