PCB Legend,silkscreen or component identification

1.Introduction

The legend of a PCB is text printed on top of the soldermask. Silkscreen or component identification are terms used for these text layers.

The silkscreen is one of the many different layers that can be found within a PCB layout design. The silkscreen layer contains all of the human#readable text to be printed onto a PCB. Such information might include component reference designators, company logos, manufacturer marks, warning symbols, part numbers, version numbers, date codes, etc.

Printable space is quite limited on the surface of a PCB, and so it should be reserved for very useful or important information. For example, the silkscreen is most often used to print a component legend, which shows the locations of various components on the board. Such a legend will ease future troubleshooting and reworking of the board, allowing technicians to easily reference between the circuit schematic and the completed PCB. Other common silkscreen applications are company logos and PCB design serial numbers.They are available in various colours which must be defined by our customer in the order details and supplied in the PCB data.

Line art and text may be printed onto the outer surfaces of a PCB usually by Liquid Photo Image able ink but we use digital printing solutions instead.
In some cases direct screen printing of the image is still used.

2.Silkscreen requirements
--In order to ensure that the silkscreen layer can be printed clearly, all silkscreen designs should adhere to the specific limits of their manufacturer’s printing equipment.Hopetimepcb is able to print silkscreen layers with a ± 7 mil (0.007 inch ) margin of error , and so we recommend that your silkscreen layers be designed with at least a 7-mil clearance from all component and board edges. In the case that this margin of error causes silkscreen to be printed over solder-able pads, our production process will automatically correct the mistake.

--Minimum Line Width & Text Height
Minimum line width refers to the lowest possible thickness of marking that a silkscreen printer can produce.We at Hopetimepcb have the capability to print PCB silkscreens with a minimum line width of 5 mil (0.125 mm).Minimum text height refersto the smallest character that a silkscreen printer can produce, in terms of physical dimensions. Hopetimepcb can print PCB silkscreen text with a minimum height of 30 mil (0.762mm).

-- Idents on Copper
Idents on Copper are permanent etchings on the PCB’s copper layer that act as labels in addition to, or in place of, the silkscreen layer. Etched lines and letters are more resistant to wear and tear, but may compromise the protections that are in place on the PCB’s copper layer.At Hopetimepcb , we offer to apply etchings onto the PCB’s copper layer, but only the ENIG or the HASL surface finish may be used in this case. Other surface finishes increase the risk of silkscreen discolouration and pollution of the exposed copper area.

--Logos
At Hopetimepcb , we certainly can print logos on silkscreen layers. However, keep in mind that all parts of your logo must also adhere to our limits in Minimum Line Width and Minimum Text Height, as outlined in Sections 8.2.1 and 8.2.2. Your CAD program should allow you to measure line width and text height once your logo is imported.

--Certificate Location
At Hopetimepcb, we offer to print certification logos onto your PCBs; simply indicate the location of these certificates in your design files.

3.Silkscreen Types
At Hopetimepcb, we offer a robust heat-curable type of silkscreen ink. Solder mask oil may also be used for printing a silkscreen layer if a custom colour is chosen.

4.Silkscreen Colours
Silkscreen lines may be printed in a wide variety of colours, and so it is useful to divide these colours into two distinct types, the standard colours and the custom colours, for the purposes of our discussion.

--Standard Colours
We at Hopetimepcb currently offer three standard silkscreen colours: White Yellow and Black.

--Custom Colours
Forthe other colour choices, we use custom-coloured solder mask oil for printing. This meansthat ourselection of custom silkscreen colours is the same as that of custom solder mask colours in here.

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