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 utilized to manufacture Quick PCB Sample for the last 20 years.

Here we are going to focus on the usage of direct digital printing to individualize PCBs just prior to their assembly. The goal is always to print a distinctive mark on each board that can be utilized to identify the board. The mark has to be permanent and 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 are going to also give attention to applications that require more that one thousand,000 boards per year. At these volumes automated material handling starts to become essential to 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 from the board. At this time digital printing can not print the entire side of any board at a cost that competes with screen printing. Even though many printers, like the PPS7000, could print all of the nomenclature on the board, here we are going to 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 placed on each Special Offer For 2layers PCB just before or after assembly. Since the product volumes ramp the reliability and cost of hand applying labels gets to be a problem. Automated systems that print and apply labels are available. (see this site ) Due to PCB space constraints these systems must place labels very accurately, a large problem for most label application systems. The labels usually are 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 technologies have 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 become a problem for the limited time its takes to dry.

Advantages

* Competitive Incremental Cost

* High Contrast Mark

* Many Colors Available

Disadvantages

* Complex Ink Viscosity Process Can Be Difficult To Manage

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

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

* Mark Not Resistant Against Some Cleaning Solvents

Laser Ablated Ink Patches – Many industries use lasers to engrave marks onto a number of parts. Lasers have been 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 be selectively removed (ablated) by the laser creating the mark to get printed. (see here ) PPSI has the capabilities to produce 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 Require A Cleaning Step

Piezoelectric Drop At Will Digital Printing, Solvent Based Ink. For any concise description of drop on demand digital printing see here [http://www.aellora.com/documents/whatisdodij.pdf]. In my opinion this alternative represents a small 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, Many Companies Seeking To Reduce Solvent Emissions

* Mark Not Resistant To Some Cleaning Solvents

Piezoelectric Drop On Demand 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 price and lead time related to 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

* Does Not Include High Volume Material Handling

Piezoelectric Drop On Demand 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 using to print on PCBs. The system 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 when they contact the PCB becoming almost solid. This enables the program 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 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 A Problem On Certain Substances

* Requires the PCB Be Clean (No Finger Oils)

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

The PPS7000 has been made to print individualizing marks on PCB Assembly using option 6. The program uses a SMEMA compatible edge belt conveyor to maneuver PCBs for the print area where they may be printed and optically inspected. After inspection these are conveyed towards the inline curing station and then out the back in 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 entire throughput from the machine is highly dependent on the number of boards in each panel. The greater boards in each panel the greater the throughput in boards a minute. A drag and drop WYSIWYG (Everything You See Is Exactly What You Receive) programming system has been developed which allows a brand new panel to become programmed in approximately 5 minutes. An offline programming system is made available.

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

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