Wednesday 16 July 2014

integrated circuit - What kind of components are black blobs on a PCB?


In low-cost mass-produced items I often run into black blobs of what looks like resin applied directly on top of something on the PCB. What are these things exactly? I suspect this is some kind of custom IC that is layed out directly on the PCB to save on the plastic housing/connector pins. Is this correct? If so, what is this technique called?


The Blob



This is a photograph of the inside of a cheap digital multimeter. The black blob is the only non-basic piece of circuitry present, along with an op-amp (top) and a single bipolar junction transistor.



Answer



It's called chip-on-board. The die is glued to the PCB and wires are bonded from it to pads. The Pulsonix PCB software I use has it as an optional extra.


The main benefit is reduced cost, since you don't have to pay for a package.


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