The electronics Printed Circuit Board industry is evolving as new production technologies become available at inexpensive. Direct digital printing is making inroads into the traditional photolithography and screen printing processes that have been used to manufacture Fast PCB Produce for the last 20 years.

Here we are going to focus on the utilization of direct digital printing to individualize PCBs just before their assembly. The goal is to print a distinctive mark on each board that can be utilized to identify the board. The mark must be permanent and definately will probably contain 1D or 2D machine readable codes together with alpha numeric characters. The marks will need to have a 600 DPI (dots per inch) resolution or better due to size constraints on the PCB. We will also give attention to applications which require more that 1,000,000 boards annually. At these volumes automated material handling starts to become very important for the overall success in the system.

High volume PCB fabricators use screen printing with thermally cured ink to print the legends that cover both sides of the board. Currently digital printing can not print the whole side of the board at a price that competes with screen printing. Even though many printers, including the PPS7000, could print each of the nomenclature on the board, here we will concentrate on using digital printing just to print the individualizing marks.

Several individualizing options exist such as the following:

Preprinted Label Application

Many low volume products get started with labels printed on office equipment and hand put on each Instant PCB Quote prior to or after assembly. As the product volumes ramp the reliability and cost of hand applying labels gets to be a problem. Automated systems that print and apply labels can be purchased. (see this site ) As a result of PCB space constraints these systems must place labels very accurately, a large problem for many label application systems. The labels are certainly not permanent. At high volumes the labels cost more than other marking methods.

Advantages

* Low Initial Cost

* High Contrast Mark

Disadvantages

* Not Permanent

* Higher Incremental Cost

* Challenging to Change Label Size On The Fly

* Mechanical Complexity For Automated Application

Solvent Based Continuous Ink Jet Digital Printing. Continuous ink-jet technologies have been adapted to mark on many industrial products including PCBs. With these systems a continuous stream of ink droplets is steered towards the desired location using electromagnetic fields. Solvent based inks produce permanent marks on porous surfaces. The marks are less permanent on non-porous surfaces where smearing may be considered a problem for the short time its takes to dry.

Advantages

* Competitive Incremental Cost

* High Contrast Mark

* Many Colors Available

Disadvantages

* Complex Ink Viscosity Process Can Be Hard To Regulate

* High Resolution (Greater Than 300 DPI) Challenging To Achieve?

* Solvents May Be Released Into Atmosphere, Many Companies Trying To Reduce Solvent Issues

* Mark Not Resistant To Some Cleaning Solvents

Laser Ablated Ink Patches – Many industries use lasers to engrave marks onto many different parts. Lasers happen to be employed to engrave marks onto PC boards with limited success as a result of absence of contrast in the resulting mark. A more modern approach is to achieve the circuit boards printed with ink patches, the ink patch will then be selectively removed (ablated) from the laser creating the mark to be printed. (see here ) PPSI has got the capabilities to build up a laser based marking system.

Advantages

* Competitive Incremental Cost

* High Contrast Mark If Ink Patch Is Used

* Very Fine, Highly Reliable Marks Provided By Laser Galvo Head

Disadvantages

* High Initial Cost

* Requires Preprinted Ink Patch

* Even At Low Power Laser heat May Damage (by Fracture) Traces, Causing Intermittent Reliability Problems

* Particle Generation May Need A Cleaning Step

Piezoelectric Drop At Will Digital Printing, Solvent Based Ink. For a concise description of drop when needed digital printing see here [http://www.aellora.com/documents/whatisdodij.pdf]. For me this option represents a little improvement over option 2.

Advantages

* Competitive Incremental Cost

* High Contrast Mark

* Many Colors Available

* Easier Process To Manage Than Continuous Ink Jet

Disadvantages

* Standoff Distance lower than 2mm, Appropriate For Unpopulated Boards Only

* Solvents May Be Released Into Atmosphere, A Lot Of Companies Trying To Reduce Solvent Emissions

* Mark Not Immune To Some Cleaning Solvents

Piezoelectric Drop At Will Digital Printing, Thermally Cured Ink. A startup company in Israel “Printar” has introduced a printer directed at low volume, fast turn PCB fabricators who want to lessen the cost and lead time related to small lot screen printing. Interesting is their thermally cured ink that reportedly has better adhesion capability than other ink systems.

Advantages

* Good Ink Adhesion ?

Disadvantages

* Requires Large Oven For 350-400 deg F Heat Cure

* Does Not Include High Volume Material Handling

Piezoelectric Drop On Demand Digital Printing, UV Cured Ink. Markem Corporation has developed an ink/print head system ( the Model 4000, see here ) that several OEMs and integrators are using to print on PCBs. The program uses an ink that is certainly less viscous at high temperature and almost solid at room temperature. The print head operates at 68 deg C, the ink drops cool once they contact the PCB becoming almost solid. This allows the system to print fine detail on PCBs without ink running or smearing. When in contact with UV light the ink undergoes a chemical reaction transforming into a solid plastic like substance. The cured ink is impervious to common solvents.

Advantages

* Competitive Incremental Cost

* High Contrast With Fine Detail (600 DPI)

* Before Cure, the Ink Can Be Wiped Off And also the Board Reprinted

* After cure, The Ink Can Not Be Removed Except By Scraping

* High volume Material Handling Available

* Works Well With Inline Inspection (Inspect Before Cure, Cure Only Good Boards)

Disadvantages

* Ink Adhesion Can Become A Problem On Certain Substances

* Requires the PCB Be Clean (No Finger Oils)

* Standoff Distance Under 2mm, Ideal For Unpopulated Boards Only

The PPS7000 has become designed to print individualizing marks on Ultrafast PCB Produce using option 6. The system uses a SMEMA compatible edge belt conveyor to maneuver PCBs for the print area where these are printed and optically inspected. After inspection these are conveyed for the inline curing station and after that out the back of the machine. When being automatically loaded by way of a board destacker, panels exit qhzwxo system about once every 10 seconds. Each panel usually contains multiple boards that each receives a unique serial number. The overall throughput of the machine is highly dependent on the variety of boards in each panel. The greater boards in each panel the larger the throughput in boards per minute. A drag and drop WYSIWYG (Everything You See Is The Thing That You Obtain) programming system continues to be developed that allows a brand new panel to get programmed in approximately a few minutes. An offline programming product is made available.

Our company is the sole PCB board marking system that produces a permanent (solvent resistant) high contrast mark, incorporates SMEMA compatible high volume material handling and incorporates inline inspection.

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