Electronic assembly and component identification is critical to electronics manufacturers to monitor and control production lots and to enable the traceability of a product throughout its useful life. This traceability is particularly useful when attempting to identify the root cause of pervasive product failures in the field, substantiating warranty claims, determining the need for product recalls, and maintaining overall quality control of the production process. The EMPF utilizes an ASYS ALS03, CO2 laser marking system to identify mission critical electronic components used in military survival radios, rechargeable battery packs and charging systems. Selecting the most effective marking system is dependent on a manufacturer’s specific application and requirements and there are three widely used marking technologies available to meet the needs of the electronics manufacturer: 1) inkjet marking systems, 2) labeling systems, and 3) laser marking systems.

Inkjet Marking Systems
Inkjet systems have become very popular in the chip and IC industry, where mostly white ink is being used to mark the black IC bodies. They are also used to mark PCBs. With the variety of colored inks available, it is not difficult to apply a mark with excellent contrast, thus avoiding any verification problems. Variations in the surface color of products have a minimal impact on marking quality. Another advantage of inkjet marking is that quick drying inks allow users to handle products in a down-stream process immediately after marking, and without the risk of smearing the code. Inkjet systems are traditionally one of the faster marking technologies available.

The disadvantages with the inkjet marking method are that inkjet marking is not considered a permanent mark, and the precision of the inkjet mark is dependent upon maintaining a constant distance between the inkjet nozzle and the product. A PCB with variances in thickness or one that has been affected by warpage could possibly generate distorted marks. The precision variables can be avoided by utilizing a system that is able to compensate for different production parameters.

Labeling Systems
Labeling Systems are commonly used to mark PCBs. Typically, a thermo-transfer printer prints a black code on a white label. The advantage here is that there is always excellent contrast. The label is then peeled off the liner material, picked up at a feeding edge, and then placed on the PCB. Depending on the printed code, cameras or scanners might require a blank area around the code, requiring a larger label than the code printed on it.

One of the challenges with using this method is the lack of available surface area on highly integrated circuit boards. The label application system must therefore be extremely accurate. Some consideration should also be given to the down-stream process, as paper labels cannot be re-flowed without turning brown and losing contrast. Bar code labeling is certainly not a permanent mark, but this attribute is sometimes quite useful in case of a printer malfunction or an unreadable code. The operator may simply peel the label off of the circuit board and re-apply another. Some systems include a verification scanner to make sure only readable labels are being applied. Some operators may prefer to verify that label codes are accurate and readable prior to application. If a label is found to be faulty, the printer can re-print and feed another to replace it. Alternately, if the label is applied prior to verification and is later discovered to be unreadable, an additional rework process is required.

Laser Marking Systems
Laser Marking, the most preferred and most recently developed marking technology, is used at the EMPF. A laser source creates a beam that is deflected by a galvo head. When the laser strikes the target material, a chemical reaction occurs that colors the material and creates the mark.

Depending on what materials need to be marked, two different lasers can be used: CO2 or YAG lasers. To mark PCBs, most engineers prefer the CO2 laser, as it produces a good contrast on the organic FR4 material. The YAG laser is normally used for components or metallic materials. As with the inkjet, the accuracy and precision of the laser mark strongly depends on maintaining a constant distance between the product and the galvo head. One of the obstacles in using a laser to mark a code directly onto a PCB is that PCBs involve the use of various coatings. Using one set of laser parameters does not ensure consistent contrast on differently coated PCBs. Those operators who employ multiple PCB suppliers will have a greater amount of difficulty with this situation.

Laser marking technology offers a cost competitive solution. While the initial capital investment is definitely larger than that associated with a label applicator, the operating expenses are significantly lower. For example, expenditures on labels would be eliminated and the maintenance requirements on a laser are extremely low. The typical lifetime of a CO2 laser source is approximately 20,000 hours. The replacement cost can be offset by the lower cost per individual mark when compared to other systems. Cost savings and rapid cycle times make laser marking a preferred method in the electronics manufacturing industry.

Since marking systems are process machines and have a significant impact on product traceability, systems providers must consult with and assist engineers in determining the proper technology for their applications. In choosing a marking system, it is important to weigh available resources, the parameters of the product, and the need for traceability.