PCBA Tech - Advantages and disadvantages of PCBA tracking barcodes

I believe that many PCB companies will use [PCBA tracking barcode] so that the factory's on-site information management system (SFCS, Shop Floor Control System or SFDC, Shop Floor Data Collection system) can track the production quality of PCBA, and this kind of [PCBA tracking barcode] There are also several ways to print, from the initial label paper printing on the bar code and then manually attaching it to the inkjet printing bar code method. Now many companies have introduced laser printing bar codes to achieve this goal.

With the advancement of technology, this [PCBA tracking bar code] has evolved from the original one-dimensional bar code to a two-dimensional bar code, which not only increases the information capacity of the bar code, but also reduces the area of the bar code required.

Introduce the advantages and disadvantages of four PCBA tracking barcode printing

The following conditions must be met when printing PCBA tracking barcodes:

▪ The barcode will not affect the appearance of the product or mislead customers.

▪ The barcode must be clear and can be read by a scanner.

▪ The barcode must be able to withstand a certain amount of friction and can be stored for more than a certain period of time. This is so that when customers respond to quality problems in the future, they can look back on the records at the time of production.

Let's try to explain the advantages and disadvantages of the four main printing methods for PCBA tracking barcodes in SMT or EMS factories:

1. Ordinary stickers and barcodes are manually attached after the furnace

This is the most traditional method of bar code printing and pasting. Choosing to paste the bar code sticker after the reflow oven is to prevent the sticker or the printed carbon ink from being heat-resistant and causing the sticker to be deformed or the handwriting to fall off. It usually requires manual attachment, which requires more manpower. Cost, and the bar code attached to the back of the furnace means that the state in front of the furnace cannot be traced at all. Sometimes even the AOI after the furnace cannot be recorded, losing the greatest effect of barcode tracking.

2. High temperature resistant sticker barcode solder paste is automatically attached before printing

High temperature resistant sticker barcode solder paste is automatically attached before printing

This is currently the most common operation used by companies. When the board is empty, the PCBA barcode is pasted. Generally, there are two methods: "automatic labeling" and "manual labeling".

To paste barcodes in front of the furnace, you must use high-temperature-resistant label materials and high-temperature carbon ink, and the cost will be slightly higher than that of ordinary stickers.

In theory, sticking a barcode in front of the furnace allows SFDC to record the quality status of the entire circuit board assembly (PCBA) operation from the SMT blank board feeding, such as the status after SPI and AOI inspection, but if you want to record it on the PCBA The parts information may face more challenges.

In addition, there is a problem with sticking barcodes in front of the furnace, which requires special attention. Because barcode stickers have a certain thickness (usually about 0.08mm), this thickness will increase the gap between the steel plate and the PCB, which will increase the amount of solder paste printing. Some parts may cause short circuits, so special attention must be paid to the pasting position to avoid pasting around finely spaced or small parts.

3. Inkjet printing barcode before solder paste printing

Inkjet printing barcodes can also be completed in the blanking stage, so it has all the advantages of [automatically attaching heat-resistant stickers and barcodes in front of the printing furnace]. The thickness of the ink is usually negligible relative to the thickness of the steel plate, which means it will not Affect the quality of solder paste printing.

Inkjet printing must use fast-drying ink, otherwise there is a risk of contamination affecting subsequent solder paste printing and poor tin eating. The disadvantage is that the ink storage environment is a bit troublesome, and the ink must be used up within the specified time after opening, and some may have to Use a UV lamp to cure the ink.

4. Laser engraving barcode before solder paste printing

Laser engraving barcode before solder paste printing

Nowadays, more and more companies begin to adopt PCB "laser engraving barcode", because it has all the advantages of [inkjet printing barcode before solder paste printing], and does not need to use ink, so there is no storage of ink and ink. Risk of pollution.

However, the biggest difference between laser engraving and the previous three methods is that laser is a method of "removing material", and the other methods are methods of adding material.

Laser engraving is mainly to remove the solder resist green paint or silk screen white paint on the circuit board and form burnt marks, so when using laser engraving, you must pay special attention to its energy not to damage the solder resist green paint or silk screen. The copper foil under the white paint, it is best not to expose the copper foil

Laser engraving is mainly to remove the solder resist green paint or silk screen white paint on the circuit board and form burnt marks, so when using laser engraving, you must pay special attention to its energy not to damage the solder resist green paint or silk screen. It is best not to expose the copper foil under the white paint, otherwise the exposed copper foil may have the risk of oxidation, which may affect the characteristics of some products. It is generally recommended to make a special area printed with white paint to make laser barcodes, which can get a better barcode recognition rate and avoid damaging the copper foil.

One more thing to note about laser engraving is that the color of the PCB solder mask is best to be "green". This is because most of the current scanning equipment uses red light. If red solder mask is used, it is almost impossible to distinguish the bar code. Welding system is also not recommended, blue solder mask is barely acceptable.