From an article by Brady Regional Product Manager Andy Schmitt

Laser-Marked PCB Labeling Solutions - When and Where

When PCB board space is limited, the need for higher resolution printing and smaller font sizes (3 points and below) is also increased. Other operational and environmental factors, including 1) surface-mount technology (SMT) reflow steps requiring high temperatures, 2) wave soldering for through-hole assemblies and 3) washing steps that prevent the use of customary thermal heat transfer (THT) print, can all become obstacles. As a result, manufacturers may decide to further automate labeling tasks, along with pick-and-place surface-mount technologies. In all of these situations, laser-marked PCB labels become a viable solution in lieu of THT printed polyester or polyimide labels.

Printing Technology Comparison Guide

* Direct marking color contrast defined by substrate and laser marking mechanism.

What is laser marking?

Laser marking uses coherent monochromatic lights to directly mark surfaces and typically includes infrared (IR) diode lasers, Nd:YAG systems or mid-IR CO2 continuous wave (CW) lasers. Each laser has different capabilities and characteristics. For instance, near IR systems are frequently pulsed to create time-limited bursts of energy while higher wavelength CO2 laser systems cannot pulse light, so basic marking is much harder. They are, however, usually less expensive, more powerful and can offer additional features such as the ability to cut.

Laser materials

Laser materials use subtractive printing and therefore, the printed layers can be fully cross-linked to create the maximum permanent identification for a coated product. Consequently, the label is more resistant to temperatures, chemicals and abrasions than THT labels.

Additionally, print resolution can be very high because the printed information is ablated in the coating with IR lasers. Resolution is limited only by the beam quality and focal optics of the laser system used, and “A” and “B” ANSI bar code grades are easily reached with these materials. Print resolution can reach as high as 600-1200 dpi allowing for small font applications.

Direct marking onto printed circuit boards will usually cost more than either THT or laser-marked labels. The most widely used material for the fabrication of electronic components is FR-4, because of its low water absorption and selfextinguishing design. However, if marked directly with a laser, the result will be very poor contrast and resolution, as well as reduced bar code grades, no-reads and longer scan times. Poor scans during production can cause identification mistakes and costly rework.

Because of its self-extinguishing characteristics, the material is also hard to ablate and boards of this nature are usually laden with bromine as the main flame retardant. The poisonous bromine gases that are produced can become a major concern when direct marking on PCB boards. Additionally, ICs and electronic components can be damaged because of the gas and moisture generated by directly marking FR4, resulting in a defective product.

When compared to THT, equipment costs and environmental health and safety requirements will be higher when integrating a laser-marking system into the workflow.

Brady offers these new products specifically designed to increase laser engraving barcode-marking legibility for printed circuit board (PCB) and component marking.

B-730: Black matte laser-markable polyimide (PI)
B-731: Black matte electrostatic dissipative (ESD) laser markable PI
B-740: Black matte polyether ether ketone (PEEK) for laser cutting
B-421: Black matte laser-markable polyester (PET)

Permanent, durable laser marking

Brady also recently introduced a solution for high-temperature applications, the Markable UltraTemp®. The label offers -

• Resistance to repeated harsh aqueous cleaning
• Resistance to high temperatures up to 300 °C during wave soldering
• Compatibility with most IR laser marking systems
• Optional ESD prevention layers
• Reduced rework issues related to direct laser-marking board materials

Hisco carries hundreds of Brady labelling products. Don’t see the one you want? We can get you any Brady product you want. Please contact us. We’re here to help.