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Reference designators help label the location on your wiring harness to make sure it is straightforward on PCB’s assembly. 

A reference designator typically consists of a single or two alphabets followed by a numerical presentation. There is a convention of using Jack (J) and Plug (P) for assigning references for the electrical connectors of a board’s assembly. 

Irrespective of the gender of each connector contact, Jack or (J) is a more fixed connector pair, whereas plug or (P) is a lesser fixed of the two. 

Does Your Board Design Need Reference Designator?

Although for some board designers, a reference designator is somewhat of an afterthought. But, if you neglect it too often, this innocuous label will begin to cause continuous trouble during your PCB assembly process. 

Hence, your CAD software automatically applies reference generators to your PCB layout. Later on, it transfers them onto the Bill of Material (BoM) without special attention. 

The automation of this process makes it easier to overlook the significance of a reference designator. So, we are going to highlight why it is important for the completion of your PCB assembly. 

How to Use a Reference Designator?

In this section, we will discuss how you can use a reference designator in assembly. With this knowledge at your disposal, you can always ensure to design a PCB assembly that is understandable and clear before you indulge in the PCB fabrication process. 

It will also help you in avoiding delays and other related mishaps due to unclear or inadequate labeling. 

Reference designators are necessary for a range of different steps during your PCB assembly process. Most notably, you will include them in the “Centroid file.” This data allows the pick and place machine to match components on your bill of material (BoM) to the actual coordinates mentioned on the PCB. 

A reference designator also plays a vital role in the Automated Optical Inspection (AOI) and Visual Inspection process. It allows you to verify whether each component is correctly in place as it should be or not. 

These labels also enable easier communication with your production team in case they have any questions or concerns about the design. Thus, the reference designator is one of the most integral and essential parts of the PCB design process. 

Is a Reference Designator Necessary?

Many PCB manufacturers ask if reference designator is even necessary for their specific designs. It is the most commonly asked question from the manufacturers working on High-Density Interconnected (HDI) boards. 

In these boards, the assembly space is extremely narrow, making it almost impossible to print reference designators onto the silkscreen layer. You may hear this question at times from other manufacturers with concerns about the aesthetics of their PCB itself. 

In such cases, the recommendation is to create an assembly drawing and submit it along with PCB design files. It is an effective way of including accurate reference designators in your BoM and Centroid files while keeping the silkscreen layer clear. 

You can ask the quality assurance team to be vigilant and double-check the assembly drawing you submitted for verification purposes. 


As far as the reference designators are concerned, you may catch minor design errors at times during your initial verification states or even while you are in the quotation and negotiation stages with the vendor.

However, this is mainly a mismatch between the Centroid or BoM or a repeated reference designator for different components. The latter is a common issue observed in panelized board designs. 

Ensure your customer services and quality management teams are efficient at catching these minor errors before the design hits the production process. However, the most recommended way to avoid this confusion entirely is to develop and adapt consistency in your reference designator design. 

Nova Engineering is ready to help you with our expert team of PCB engineers. Contact us today!