Choosing a PCB Printing Solution

PCB

The electronic equipment Printed Circuit Board industry is evolving as new production technologies become available at low cost. Direct digital printing is now making in roads into the traditional photolithography and monitor printing processes that have been used to fabricate PCB for the previous 20 years.

Here we’ll focus on using guide electronic printing to individualize PCBs just prior to their own meeting. The aim is to print a unique mark on each plank which can be used to spot the board. The mark has to be permanent and will most likely contain 1D or 2D machine readable codes together with alpha numeric characters. We’ll also concentrate on applications that want longer that 1,000,000 boards per year. These volumes automated material handling starts to become very crucial to the overall success of the system.

High-volume PCB fabrication utilize screenprinting using thermally cured ink to print the legends that cover each side of this plank. Only at that time digital printing cannot print the whole aspect of a board at a price that competes with screen printing. Even though many printers, including the PPS7000, could print all of the nomenclature on the board, here we’ll concentrate on using digital printing only to print the individualizing marks.

Several individualizing options exist including the following:

Pre-printed Tag Tool

Many low volume services and products focus on labels published on office equipment and hands applied to each PCB prior to or after assembly. As the item volumes ramp the durability and price of hand employing tags becomes a problem. Automated systems which print and apply labels are all available. (see this site ) Due to PCB distance limitations these systems must place labels very accurately, a big problem for most label application methods. The tags aren’t permanent. At high volumes the labels are pricier compared to other marking techniques.

Advantages

  • Low Preliminary Cost
  • High-contrast Mark

Cons

  • Not Permanent
  • Higher Incremental Cost
  • Difficult to Modify Label Size About Your Fly
  • Mechanical Complexity For Automated Tool

Solvent Based Continuous Inkjet Digital Printing

Continuous ink-jet technology has been adapted to indicate on many industrial products including PCBs. With all these systems a continuous stream of ink droplets is directed into the required location using electromagnetic fields. Solvent based inks produce permanent marks on porous surfaces. The marks are somewhat less durable on nonporous surfaces at which smearing could possibly be a problem for the short period its takes to dry.

Advantages

  • Competitive Incremental Cost
  • High Contrast Mark
  • Lots Of Colors Available

Cons

  • Complex Ink Viscosity Process Might Be Hard to Regulate
  • High Resolution (More than 300 DPI) Difficult To Achieve?
  • Solvents Might Be Released Into Atmosphere, Many Businesses Seeking to Cut Back Solvent Issues
  • Mark Not Resistant for Some Cleaning Solvents

Laser Ablated Ink Patches

Many industries use lasers to engrave marks onto various parts. Lasers are used to engrave marks onto PC boards with limited success due to the lack of comparison of the resulting mark. (see here ) PPSI has the capacities 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 Available With Laser Galvo Head

Disadvantages

  • High Preliminary Cost
  • Requires Pre-printed Ink Patch
  • Even At Low Power Laser warmth Might Damage (by Fracture) Traces, Causing Intermittent Reliability Problems
  • Particle Generation May Require A Cleaning Measure

Piezo Electric Drop On Demand Digital Printing, Solvent Based Ink

For a concise description of drop on demand digital printing see here [http://www.aellora.com/documents/whatisdodij.pdf]. In my estimation this option represents a small improvement over option 2.

Advantages

A startup business in Israel”Printar” has recently introduced a printer targeted at low volume, speedy turn PCB fabricators who must reduce the cost and lead time involved with little screen screen printing. Interesting is their thermally cured ink that reportedly has better adhesion capability than some other ink technologies.

Advantages Cons

  • Demands Enormous Oven For 350 400 deg F Heating Cure
  • Will Not Include High-volume Material Handling

Piezo-electric Drop On Demand Digital Printing, UV Cured Ink

The system uses a ink which is less viscous at high temperatures and nearly solid at room temperature. The print head operates at 68 deg C, the ink drops cool whenever they get into the PCB becoming nearly solid. This allows the system to print fine detail on PCBs without ink running or smearing. When confronted with UV light that the ink expands a chemical reaction becoming a solid plastic such as chemical. The treated ink is more impervious to common solvents.

Advantages

  • Competitive Incremental Cost
  • High Comparison With Nice Detail (600 DPI)
  • Before Cure, the Ink Could Be Wiped Away And the Board Re-printed
  • After cure, The Ink Cannot Be Performed Except By Scraping
  • High quantity Material Handling Available
  • Is Effective With Inline Inspection (Inspect Before Cure, Cure Only Excellent Boards)

Cons

  • Ink Adhesion May Be A Problem On Certain Substances
  • Requires the PCB Be Clean (No Finger components )
  • Standoff Distance Significantly Less than 2mm, Proper For Un-populated Boards Only

The PPS 7000

The system employs a SMEMA compatible border belt conveyor to go PCBs to the print area where they are printed and optically scrutinized. After review they are hauled into the in line curing station and out the back of the machine. When being automatically loaded by means of a plank destacker, panels exit the system about once every 10 minutes. Each weapon usually contains multiple boards which every receives a exceptional sequential number. The total throughput of the machine is highly determined by the number of planks in each panel. The more boards in each panel that the higher the throughput in planks each second. A drag and drop WYSIWYG (What You Watch Is What You Get) programming system was developed which allows a new panel to be programmed approximately 5 minutes. An offline programming system can be available.

We’re the sole PCB board signaling system that creates a permanent (solvent resistant) high contrast mark, integrates SMEMA compatible high volume material handling and incorporates in line inspection.

Next Steps

In case the PPS7000 looks like it can satisfy the needs you have the next step is to publish samples to you as a way to verify that the ink will stick nicely to your substrates.

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