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

Here we shall focus on the use of direct digital printing to individualize PCBs just before their assembly. The aim would be to print a unique 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 should have a 600 DPI (dots per inch) resolution or better due to size constraints on the PCB. We will also give attention to applications that need more that 1,000,000 boards annually. At these volumes automated material handling starts to become extremely important to the overall success of the system.

High volume PCB fabricators use screen printing with thermally cured ink to print the legends that cover each side from the board. At the moment digital printing can not print the entire side of a board at a cost that competes with screen printing. Even though many printers, including the PPS7000, could print all the nomenclature on the board, here we are going to give attention to using digital printing simply to print the individualizing marks.

Several individualizing options exist including the following:

Preprinted Label Application

Many low volume products begin 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 becomes a problem. Automated systems that print and apply labels can be found. (check this out site ) Because of PCB space constraints these systems must place labels very accurately, a huge problem for most 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

* Hard to Change Label Size On The Fly

* Mechanical Complexity For Automated Application

Solvent Based Continuous Ink Jet Digital Printing. Continuous ink-jet technology has 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 a problem for that short period of time its takes to dry.

Advantages

* Competitive Incremental Cost

* High Contrast Mark

* Many Colors Available

Disadvantages

* Complex Ink Viscosity Process Can Be A Challenge To Regulate

* High Resolution (In Excess Of 300 DPI) Hard To Achieve?

* Solvents May Be Released Into Atmosphere, A Lot Of 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 a number of parts. Lasers have already been utilized to engrave marks onto PC boards with limited success as a result of insufficient contrast from the resulting mark. A more modern approach is to achieve the circuit boards printed with ink patches, the ink patch will be selectively removed (ablated) from the laser creating the mark to become printed. (see here ) PPSI has the capabilities to produce a laser based marking system.

Advantages

* Competitive Incremental Cost

* High Contrast Mark If Ink Patch Is Used

* Very Fine, Highly Reliable Marks Provided With 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 Demand A Cleaning Step

Piezoelectric Drop At Will Digital Printing, Solvent Based Ink. To get a concise description of drop on demand 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 Regulate Than Continuous Ink Jet

Disadvantages

* Standoff Distance under 2mm, Appropriate For Unpopulated Boards Only

* Solvents May Be Released Into Atmosphere, Many Companies Attempting To Reduce Solvent Emissions

* Mark Not Resistant To Some Cleaning Solvents

Piezoelectric Drop When Needed Digital Printing, Thermally Cured Ink. A startup company in Israel “Printar” has introduced a printer directed at low volume, fast turn PCB fabricators who require to minimize the cost and lead time connected with small lot screen printing. Interesting is the 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

* Fails To Include High Volume Material Handling

Piezoelectric Drop When Needed Digital Printing, UV Cured Ink. Markem Corporation has evolved an ink/print head system ( the Model 4000, see here ) that several OEMs and integrators are utilizing to print on PCBs. The system uses an ink that is certainly less viscous at high temperature and almost solid at room temperature. Paper head operates at 68 deg C, the ink drops cool once they contact the PCB becoming almost solid. This permits the system to print fine detail on PCBs without ink running or smearing. When subjected to UV light the ink undergoes a chemical reaction being 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 the Board Reprinted

* After cure, The Ink Can Not 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 Be Considered A Problem On Certain Substances

* Necessitates the PCB Be Clean (No Finger Oils)

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

The PPS7000 continues to be designed to print individualizing marks on Ultrafast PCB Produce using option 6. The device utilizes a SMEMA compatible edge belt conveyor to maneuver PCBs for the print area where they are printed and optically inspected. After inspection they are conveyed to the inline curing station then out the back in the machine. When being automatically loaded with a board destacker, panels exit qhzwxo system about once every 10 seconds. Each panel usually contains multiple boards that every receives a unique serial number. The general throughput of the machine is extremely dependent on the variety of boards in each panel. The more boards in each panel the higher the throughput in boards each minute. A drag and drop WYSIWYG (Everything You See Is Exactly What You Get) programming system continues to be developed which allows a whole new panel to be programmed in approximately 5 minutes. An offline programming product is available too.

We have been the only PCB board marking system that creates a permanent (solvent resistant) high contrast mark, incorporates SMEMA compatible high volume material handling and incorporates inline inspection.

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