LABELING PCBS:
A MODERN APPROACH
Abstract: Manufacturers of printed circuit boards (PCBs) and other electronics require
a label printing solution that delivers durable, high quality labels that can withstand
the harsh manufacturing processes these products undergo. ARMOR-TT, the leading
provider of thermal transfer printing solutions, introduces an innovative new resinbased thermal transfer ribbon, compatible with flat-head thermal transfer printers and
compliant with industry regulations. It’s the modern approach to labeling PCBs and
other electronics.
• TABLE OF CONTENTS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Mounting and Fixing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
The Board Cleaning Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Labeling PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Reinventing PCB Label Printing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Thermal Printing 101. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Thermal Transfer for PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
NEW: AXR®EL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
The Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
For More Information … . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
INTRODUCTION
In the age of the Internet of Things, where it seems that just about everything is connected, there is growing
demand for printed circuit boards (PCBs). They are in everything from automobiles to phones, home appliances
and wearable technology, largely because manufacturing circuits with PCBs is faster and less expensive than
other wiring methods.
While the manufacture of PCBs is a fairly mature industry, there are still challenges in the manufacturing process,
not the least of which is continued downward price pressure, track-and trace, and the need to incorporate more
components onto a single board or chip. Often for eciency, a number of PCBs are grouped for manufacturing
onto a larger board, in a process called panelization, to create arrays, which are eventually separated into individual PCBs for incorporation into a final product.
The designed pattern for the board can be applied using additive or subtractive processes. This is complex but
can be simply described as follows:
• In a subtractive method, copper is removed from an entirely copper-coated board to leave only the desired
pattern.
• In the additive method, the pattern is electroplated onto a bare substrate following a chemical etching process,
resulting in less waste.
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LABELING PCBS:
A MODERN APPROACH
MOUNTING AND FIXING COMPONENTS
Components can be mounted on the board using two dierent technologies:
• With Surface Mount Technology (SMT), components are mounted or placed directly
onto the surface of PCBs as an alternative to Through-hole components.
• With Through-hole technology (THT) components are fitted with wire leads into holes in
the circuit board.
Component fixation is ensured by soldering which can be accomplished in two ways:
• Brazing by reflow, suitable for SMT component cards, where a sticky mixture of powdered solder and flux
(several kind of flux exist, and they include No-clean, RMA or water washable fluxes). The mixture, called solder
paste, is used to attach electrical components to a board. This paste is applied to solder pads typically using
a silk screen process, or alternatively, using an ink jetting process. SMT components are then placed on the
board by a pick-and-place machine. Boards are then passed through a reflow soldering oven where temperature goes through cycles reaching 200°C, melting the solder and bonding the component leads to the pads
on the circuit board. This is a significantly faster process, obviously, than manual soldering. In another heating
process, boards are also often placed in ovens to remove any moisture that might have accumulated on the
board during the manufacturing process, generally at a temperature of 120°C or more (above the boiling point
of water).
• Another method is Wave Soldering, suitable for SMT and THT mixed PCBs. This process uses glue in a first step if needed, and a pan of molten solder in which a pump
produces an upwelling of solder that looks like a standing wave. SMT components are
placed on the board with glue. The board is placed in the oven and the glue is polymerized/melted. THT components are placed on the other side of the board. The board is
then passed over a pan of molten solder. As the circuit board makes contact with this
wave, the components become soldered to the board.
As Through-hole components have been largely replaced by surface mount components, wave soldering has
been largely supplanted by reflow soldering methods in many large-scale electronics applications. However, there
is still significant wave soldering where surface-mount technology (SMT) is not suitable (e.g., large power devices
and high pin count connectors), or where simple Through-hole technology prevails (certain major appliances).
THE BOARD CLEANING PROCESS
After soldering, the boards may be washed to remove flux residues and any stray solder balls that could
short out closely spaced component leads. Cleaning solutions can be solvent- or water-based.
• Water-based cleaning solutions are compatible with plastics and metals, but not items that use fluorine.
• Solvent-based cleaning solutions are compatible with plastics but not all metals, such as aluminum.
Co-solvents are used with these solvent-based cleaning solutions and can include Hydro Fluoro Ether
(HFE) or Hydro Fluoro Carbon (HFC).
There are four dierent washing processes:
Cleaning solution mixtures and bathing/washing duration can vary depending on processes and users, but practices can for instance include the following:
• Immersion/bath uses a mix of about 70% water-based solution and 30% demineralized water which is heated
to 54°C. The PCB is bathed in this mix with light agitation for about 5 minutes and then rinsed in a demineralized bath. The PCB is then dried with hot air at a temperature varying from 55°C to 80°C.
• Also with a water-based cleaning solution, boards can be placed in a special Washing Machine using mix of
about 70% water-based solution and 30% demineralized water at a temperature of 60°C for 5 minutes with
light agitation. The PCB is then rinsed twice in the same machine with demineralized water for 200 seconds
each. It is then dried for 10 minutes with 80°C hot air.
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LABELING PCBS:
A MODERN APPROACH
• A low-pressure wash can be used with solvent-based cleaning solution (HFC or modified alcohol). PCBs are
placed on a rack and inserted into a low-pressure chamber into which solvent is released. In this process, the
solvent containing residues from the board cleaning is transferred to a distillation chamber, evaporated leaving
residues in the bottom of the chamber, with the solvent re-condensed for re-use.
• Also for solvent-based cleaning solutions, a vapor phase cleaning process can be used. This typically uses
a solvent-based solution and HFE mixed together or separately. As a first step, PCBs are bathed for about 5
minutes in the mixture of solvent-based solution and HFE solvents with light agitation. They are then transferred to a pure HFE bath where they bathe for about 2 minutes. The board is then exposed to the HFE in a vapor
phase for two minutes for additional rinsing, and eventually dried in a cool area where the solvent is condensed
back to a liquid state for re-use.
LABELING PCBs
Most of these manufacturing and cleaning processes are quite corrosive and
involve high temperatures which puts a strain on PCB labeling.
These labels often contain legends or other information identifying the PCB itself
or its components, switch settings, test points and other information that is used
during the intermediate or final assembly process, as well as for testing and servicing the board. Labels are also critical to the logistics and track-and-trace process.
Labeling of PCBs is a critical element of the manufacturing process. Traditionally, silk screening with an epoxy ink
was used. This is ideal for long runs of boards or panels that all bear the same information. However, it does not
allow for the application of variable information on these boards, including bar codes and serial numbers. Variable
data traditionally is added in a second stage of printing using a dierent technology.
PCB labeling must be able to withstand the harsh processes described above, including:
• Heating cycles at high temperatures; some processes require heat at temperatures as high as 280°C or more.
• Cleaning cycles, often using harsh solvents with dispersal under high pressure.
• Varnishing and coating.
• Heat generated by the finished product in-use or to which the finished product is exposed.
Since labels are often quite small, high definition printing with strong blackness is also required, especially for
barcodes, alpha-numeric characters and logos. This can be dicult to achieve with many of the etching processes
described above. In addition, labels must comply with a number of regulations.
This white paper discusses a mean of digitally labeling PCBs and other electronics that are subject to heat, pressure and chemicals in the manufacturing and inuse process, enabling full board labeling, including variable data, in a single pass.
This streamlines the labeling process, taking out time and cost and eliminating
the need for a two-pass labeling process to incorporate variable data. It also
makes labeling of prototypes and short board runs more cost-eective.
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LABELING PCBS:
A MODERN APPROACH
Reinventing PCB Label Printing
In the manufacture of PCBs, durable, high quality labels that are resistant to heat, pressure and chemicals are
critical. Yet the label production process must be flexible and aordable. So how do you make the right choices
to ensure the eectiveness of PCB labels across the entire supply chain and product life cycle? In their quest for
increased quality and eciency, reduced cost and faster time to market, PCB manufacturers are increasing turning to digital printing technologies for the production of PCB labels, including the application of both fixed and
variable data in a single pass. Durability, quality and cost are key decision points in choosing a labeling process,
and thermal transfer printing ticks all the boxes.
THERMAL PRINTING 101
For those not familiar with thermal printing, there are two types of thermal printing. But there is a big dierence
between the two!
• Direct thermal label printing requires a heat sensitive label material. Print head elements come into
direct contact with the material to create the printed image. While there have been improvements in
this technology over the years, the direct contact with the material can cause wear on the print heads
resulting in frequent head changes. In addition, the label material can be susceptible deterioration
when exposed to heat, light, abrasion and other factors that reduce the usable life of a label. This process is not suitable for printing PCB labels.
• Thermal transfer label printing uses a thermal transfer ribbon. Print head elements heat the back side
of the ribbon to transfer the ink, bonding it to the media. Because there is no direct contact between
the media and the print head, print head life is typically 25% to 50% longer, reducing costs and downtime due to head changes. It is the most widely used technology worldwide for printing variable data
associated with traceability.
In the manufacture of printed circuit boards, there are two other marking techniques that can be used that also
enable the application of text or other labels to the board: Inkjet printing and laser etching.
Laser etching has a benefit over chemical etching in that it uses less hazardous chemicals and can be used in a
normal oce environment, although it does need to be vented. It is most often used for prototyping PCBs and
small quantities of custom boards. An optical mask, such as black paint, is applied, and the laser is used to etch
away the paint where copper is to be removed in a subtractive process. The remaining paint protects the copper
from the etchant, but where the paint has been burned away, the copper is exposed and removed by the etchant.
Once copper is removed, the remaining paint is removed, leaving the copper pattern. Text or labels can also be
applied in this way, although depending on the laser settings, the text resolution may not be ideal.
Inkjet printing of PCB patterns typically requires adjustments to standard inkjet printers and pigment inks that can
be cured with heat to stand up to etching materials, forming a strong resist. The result is the ability to use inkjet
printers with pigment-based inks to feed and directly print resist patterns to copper clad printed circuit board
stock, ready for etching with Ferric Chloride, Cupric Chloride, or some other etchant. The printer can also be used
to apply a solder mask and/or a component silk screen. Boards printed using this technique need to be carefully
checked, since it may result in incomplete or light traces.
While these methods can be used to apply labels to PCBs, neither is suited for higher volumes of production.
The bottom line: Thermal transfer labeling quickly rises to the top of the list in terms of choices for labeling PCBs.
With new resin-based ribbons that are able to deliver the high resolution required by often small labels and small
type as well as to resist the harsh conditions associated with the manufacture of PCBs, thermal transfer printing
is the ideal solution to faster, higher quality and more ecient PCB labeling.
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LABELING PCBS:
A MODERN APPROACH
THERMAL TRANSFER FOR PCBs
ARMOR, the global leader in thermal transfer technologies, is introducing an innovative resin-based thermal transfer ribbon designed specifically for printing labels for PCBs and other electronics. It features excellent resistance
to heat and solvents while delivering high quality print and complying with key regulations.
In business for more than 90 years, ARMOR has more than 2,000 employees around the globe, including more
than 40 engineers and R&D researchers. ARMOR prides itself on the quality of its manufacturing, with a 99.8%
conformity rate for its products monitored by its 48 quality control professionals. The company sold more than
one billion square meters of thermal transfer ribbon in 2016, and is generating high double-digit growth. This
makes ARMOR the ideal partner for manufacturers of PCBs and other electronics looking for stability, reliability
and innovation.
In addition to excellence in product quality and innovation, ARMOR is also committed to social innovation, including sustainable development, a strategic element that permeates all its businesses. Socially Responsible Innovation guides its customer product lines, including full product recycling and the monitoring of the associated
carbon footprint.
Socially Responsible Innovation also manifests itself on a day-to-day basis in all of ARMOR’s activities. By placing
Social Innovation at the heart of its strategy, ARMOR invests to protect its long-term interests and those of its
customers, employees and investor partners... and to some extent, future generations.
NEW from ARMOR: AXR®EL
As described in this white paper, PCB labels are subjected to significant stress throughout the production process. Poor quality or damaged printing can have an impact on production process monitoring, on logistics and on
the use of the printed circuit board in the end product.
Message legibility and durability requirements are at the heart of the process of selecting a print solution. That’s
why ARMOR is introducing AXR®EL, a brand-new resin-based thermal transfer ribbon for flat-head printers that is
designed specifically to address the labeling needs of PCBs and other electronics, including:
• Power storage and conversion
• RFID
• Opto-electronics
• Embedded electronics
• Micro-electronics
to ARMOR
• Sensors … and more.
AXR®EL is ideal for use by PCB manufacturers and other industries that require durable, aordable high quality
labeling, including military, aeronautics, nuclear and pharmaceutical applications. It is compatible with the most
common PCB and electronics labels on the market, including Polyester, Acrylate and Polyimide.
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LABELING PCBS:
A MODERN APPROACH
THE DETAILS
Thermal Transfer technology is the most reliable print technology for printing unitary information on printed circuit
board labels. The high definition of the print head produces extremely accurate printing of all types of barcodes
(vertical, horizontal, datamatrix, 2D, etc.), alphanumerical characters and logos, even on very small labels. AXR®EL
specialized resin-based ribbon is:
• Resistant to temperatures up to 300°C.
• Resistant to PCB varnish and solvents, including isopropyl alcohol, Exxsol, Atron, Vigon and Aquanox.
• Durable, with high mechanical resistance to scung and abrasion.
• Compatible with 600 dpi flat-head thermal transfer printers from industry suppliers such as Avery Dennison,
Datamax, Intermec, Sato, Toshiba and Zebra.
• Fast, printing at a speed of up to 150mm/second.
• Certified:
- Halogen free, tested using EN 14582 : 2007
- Compliant with EU Directives 2011/65/EC (RoHS) and 2002/96/EC (WEEE) as well as REACH
SVHC:1907/2006/CE
- Meets UL standard for printed label durability.
- IPC A-610-F: Acceptability of Electronic Assemblies.
- EN 50419: Marking of Electrical and Electronic equipements.
FOR MORE INFORMATION …
For more information about thermal transfer printing for PCB manufacturing or other ARMOR products,
contact :
· For ASPAC Region: Ms. Eileen ANG ([email protected])
· For AMERICAS Region: M. Olivier MOREAU ([email protected])
· For EMEA Region: Miss Marie-Noelle NGUYEN ([email protected])
Or visit www.armor-tt.com.
Thermal Transfer is the most widely
wid l used
d
technology for printing variable information on
6
labels or packaging.