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

Here we shall focus on the utilization of direct digital printing to individualize PCBs just before their assembly. The goal is to print a unique mark on each board that can be utilized to identify the board. The mark should be permanent and definately will probably contain 1D or 2D machine readable codes along with alpha numeric characters. The marks will need to have a 600 DPI (dots per inch) resolution or better because of size constraints on the PCB. We will also focus on applications which require more that 1,000,000 boards each year. At these volumes automated material handling actually starts to become essential for the overall success from 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 entire side of a board at a cost that competes with screen printing. Even though many printers, such as the PPS7000, could print each of the nomenclature on the board, here we shall 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 begin with labels printed on office equipment and hand applied to each Instant PCB Quote before or after assembly. As the product volumes ramp the reliability and price of hand applying labels turns into a problem. Automated systems that print and apply labels are available. (check this out site ) As a result 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 can be more expensive than other marking methods.

Advantages

* Low Initial Cost

* High Contrast Mark

Disadvantages

* Not Permanent

* Higher Incremental Cost

* Difficult 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 to 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 your 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 Difficult To Regulate

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

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

* Mark Not Immune To Some Cleaning Solvents

Laser Ablated Ink Patches – Many industries use lasers to engrave marks onto a variety of parts. Lasers happen to be used to engrave marks onto PC boards with limited success because of the lack of contrast in the resulting mark. A more modern approach is to get the circuit boards printed with ink patches, the ink patch is then selectively removed (ablated) through the laser creating the mark to be printed. (see here ) PPSI provides the capabilities to develop a laser based marking system.

Advantages

* Competitive Incremental Cost

* High Contrast Mark If Ink Patch Can Be 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 On Demand Digital Printing, Solvent Based Ink. For a concise description of drop at will digital printing see here [http://www.aellora.com/documents/whatisdodij.pdf]. In my opinion this alternative represents a slight 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 less Than 2mm, Suitable For Unpopulated Boards Only

* Solvents May Be Released Into Atmosphere, Most Companies Trying 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 targeted at low volume, fast turn PCB fabricators who want to lessen the cost and lead time associated with 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 At Will Digital Printing, UV Cured Ink. Markem Corporation has created an ink/print head system ( the Model 4000, see here ) that several OEMs and integrators are employing to print on PCBs. The program uses an ink which is less viscous at high temperature and almost solid at room temperature. Paper head operates at 68 deg C, the ink drops cool whenever they contact the PCB becoming almost solid. This permits the program to print fine detail on PCBs without ink running or smearing. When subjected to 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 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, Suitable For Unpopulated Boards Only

The PPS7000 has been made to print individualizing marks on Ultrafast PCB Produce using option 6. The system uses a SMEMA compatible edge belt conveyor to go PCBs to the print area where these are printed and optically inspected. After inspection these are conveyed to the inline curing station and then out the back of the machine. When being automatically loaded by a board destacker, panels exit qhzwxo system about once every 10 seconds. Each panel usually contains multiple boards that each gets a unique serial number. The overall throughput of the machine is extremely dependent on the variety of boards in each panel. The more boards in each panel the greater the throughput in boards a minute. A drag and drop WYSIWYG (Whatever You See Is The Thing That You Receive) programming system has been developed that enables a new panel to become programmed in approximately 5 minutes. An offline programming system is available too.

We have been the only real 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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