Quality Control Standards


A list of the standards used for quality control
More info

Controlled Impedance


Impedance is the sum of the resistance and reactance of an electrical circuit expressed in Ohms. The resistance being the opposition to current flow present in all materials. The reactance is the opposition to current flow resulting from the effect of the inherent capacitance and inductance of the conductor interacting with changes in voltage and current. In DC circuits there is no reactance and the resistance of copper conductors is typically insignificant. However in high speed AC circuits (those with sharp changes in voltage and/or current) the reactance and thus the impedance can become very significant. This can become critical to a design's functionality because of the effects that changes in the impedance along the signals path from transmitter to receiver will have on the efficiency of power transfer as well as signal integrity. While a circuit’s speed is often expressed as the frequency of the wave form: the critical concern is the speed at which the voltage and/or current is required to change.

Our printed circuit board manufacturers specialize in different areas of PCB manufacturing, giving us the unique ability to not only build your boards economically, but to also maintain the highest quality standards. Because of our high order volumes we have negotiated pricing much lower and we believe you cannot find a better value anywhere else.

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Quality

We incorporate a Design Rules Check (DRC) in our manufacturing and fabrication processes as a quality control test. For new orders, we initially address layout problems by using an automated testing machine to verify that the layout does not have routing, placement, or any other layout problems. Using the DRC, we compare the layout and the net list to PCB design limitations and the rules. It will verify part placement and trace routing to make sure there is no overlapping, untraced connecting pins, incorrect layer placements or other limitations that have been determined for routing widths and clearances.

Controlled Dielectric


The typical design considerations involved in the determination of the requirement for controlling the impedance are the strength of the signals involved, the susceptibility of the circuit to noise and signal distortion, the criticality of signal timing and the speed at which the signal’s source is attempting to force a change in voltage and/or current.

The design considerations for setting the value of the impedance for the conductor is typically the output impedance of the transmitter and the input impedance of the receiver. The impedance of other conductors (i.e. coaxial cables) in the circuit path will also need to be considered. The acceptable range (tolerance) for the impedance will need to be determined and taken into account during the design phase as well as when specifying the PCB parameters. In many cases merely by using software models to determine the anticipated impedance with particular dielectric materials and spacing, followed by requesting these parameters be followed when the PCB’s are fabricated will suffice. This is what we call “controlled dielectric”. For more critical applications you will need to specify “controlled impedance” and supply the actual impedance requirements for the conductors and we will fine tune the dielectrics and conductors to meet these requirements. The impedance requirements will have to be specified based on the layer and the conductor widths.

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