Trimming LTCC resistances in a pressure
Trimming LTCC resistances in a pressure chamber
One type of passive trimmer uses a pressure chamber to enable resistor trimming in a single run. The LTCC boards are contacted by test probes on the assembly side and trimmed with a laser beam from the resistor side. This trimming method requires no contact points between the resistances, because the fine pitch adapter contacts the component on the opposite side of where the trimming occurs. Therefore, the LTCC can be arranged more compactly and less expensively.
The LTCC is mounted in the contact unit.
From the opposite side a rigid probe contacts the circuit.
From the top side the chamber is pressurized to 1 to 4 bars, with a controlled exhaust port to achieve air flow through the chamber.
As the resistance material is vaporized, the waste particles are removed in the air flow.
Advantages of this method:
Trimming of unlimited number of printed resistors in one step without obstruction from test probes.
No contamination on board, adapter or in system.
Density up to 280 points/cm².