Premold packages

Due to the nature of sensing intensive physical parameters (i.e., pressure, flow, etc.) the sensor has to have access to the environment to be sensed. Thus mold packages are inappropriate, but premolded packages may be an alternative (Fig. 5.8.3). Although more expensive than the standard mold package, the pre-molded version offers the required accessibility and retains many of the typical mold package advantages, especially when the external dimensions are kept standard. 

When molded or premolded packages cannot be used for whatever reason, for example, a need for hermetic sealing, modules using ceramic substrates (or PCB-printed circuit board) offer almost unlimited flexibility. They can be used for simple multichip modules containing two or more elements (e.g., a sensing element and an evaluation circuit), may include external components, or may be used to construct complete systems. Stress-optimized package configurations for sensitive microsystems and sensors are no problem (Fig. 5.8.4). 

Leaded ceramic chip carrier (LDCC), leaded ceramic chip carrier packages include JEDEC types A, B, C, and D. Leaded type B parts are direct soldered to a substrate. Leaded type A parts can be socketed or direct soldered, and include sub-categories leaded ceramic, premolded plastic, and postmolded plastic (which are not designated as LDCC devices). 

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