QUESTION #1: How are Polyimide label & Kapton label stock different?
ANSWER: They are not. Kapton is DuPont's tradename for it's brand of polyimide film. Although there are certain chemical differences between DuPont's "flavor" as compared to others, as in the famous "Coke vs. Pepsi" debate, the differences are inconsequential when used as a base for label materials.

The tables below show which ribbon you should use for a particular label stock. If you compare them, you'll see that polyimide label and kapton label materials are identical:
Kapton Label Stock Product Line

Polyimide Label Stock Product Line

The main point to remember is that polyimide label material, whether it be DuPont's Kapton label material or some other polyimide, is used for high temperature bar code labels because it survives the high temperatures required for circuit board manufacturing, without shrinking or melting. This provides a stable base for the printing on the surface enabling the bar code symbology to remain within ANSI standards. Also, it makes no difference for UL recognition whether or not Kapton label material or polyimide label material is used as the film base. They are interchangeable in UL's opinion. Of course, each was tested just to make sure !!

See also Polyonics Kapton Labels for the DuPont recognition of Polyonics excellent Kapton label materials, or go to the DuPont site DuPont Kapton Label Material to see it in its original glory. On the DuPont site you can download a pdf version of this product information.

QUESTION #2: Why can you use wax ribbons for printing on polyimide labels or kapton labels for printed circuit board labels? Doesn't the wax based print smear off in the high heat of pcb soldering?
ANSWER: Contrary to your first instinct, wax ribbons CAN BE USED on properly matched label material, even when the label is to be exposed to temperatures up to 800 degrees F. The label stock surface must be matte (or microporous) so that the melted wax (which by now at that high temperature is now like a liquid ink) will be absorbed into the pores, just as a wet ink is absorbed into the pores of paper. In fact, if you print with a wax ribbon on a glossy surface, and then subject it to the same high temperatures, it WILL smear and run, since the now-liquid ink has "no place to go".

Click on the links below to see several examples of this. The products XF 541 and XF 565 use wax ribbons, as shown.
Polyimide Label Stock Product Line

XF 541 Polyimide Label Material

XF 565 Polyimide Label Material

Please contact Polyimide Label Support for recommendations of ribbon/label stock combinations which WILL perform well, including WAX ribbons on matched polyimide or kapton label materials. Ask for our FREE Thermal Ribbon Directory !!

QUESTION #3:What is the operating temperature for kapton label materials?
ANSWER:Effective Service Temperatures depend not only on the external or applied temperature, the mass of material the label is to be adhered to, and the heat source, but also the length of time that the label is exposed under those conditions. For example, XF-557 can withstand temperatures up to 1,000°F (538°C ) for about 7 seconds. It performs well at temperatures greater than 700°F (371°C) for 10-15 minutes, and above 500°F(260°C ) for 12-24 hours. Similarly, the other THERMOGARD® products exhibit their own time/temperature effective service profile. Test each material thoroughly for individual process times and temperatures.

For example,the Data Sheet for XF 555 Polyimide Label Material reveals the following:

Short Term High Service Temperature
5 minutes at 500°F (260°C) No visible effect to label at 260°C, label discolors slightly at 270°C, 300°C label moderately discolors Label remains functional.

2 hours at 338°F (170°C)
No visible effect to label at 170°C, label discolors slightly at 190°C, moderately at 220°C severely at 260°C. Label remains functional.

Long Term High Service Temperature
1000 hours at 212°F (100°C) No visible effect to label at 100°C label discolors slightly at 120°C moderately at 145°C. Label remains functional.

QUESTION #4: My company recently switched thermal transfer ribbon vendors. We went from one type of "premium resin ribbon" from the first vendor to the second company's version of the same type of "premium resin ribbon". The printed image on the polyimide labels were excellent, but the barcodes printed with the new ribbon washed off the label in our manufacturing process. Why?

ANSWER: You have hit squarely on an example which proves something we've observed over the years. First, and foremost, all "resin ribbons" are not "created equal".The matching of ribbons and label stocks is critical to the successful implementation of bar code systems, PARTICULARLY when chemical resistance is required. Second, there is no single ribbon/label stock combination which will survive all the chemicals used in electronics manufacturing. Once a label/ribbon combination is proven, only change it after exhaustive testing of the new materials. Similarly, if you contemplate a manufacturing process change, don't forget to test the current label in the new process.

ALternatively, you can obtain a PCB Process Test Kit from Polyonics to establish a new polyimide label and ribbon combination for the new process. You can download a pdf document "Thermal Transfer Printing for Harsh Environments", written by Dr. Jim Williams, Polyonics' founder, which discusses this further. Click on Document Center .

QUESTION #5: Since there are dozens of ribbon/label combinations available to try, what is the best way to begin evaluation of polyimide labels for marking circuit boards?
Answer: The best way to determine the optimal polyimide label and thermal transfer ribbon combination, is to test several combinations at once. Fortunately, Polyonics has put together a PCB Process Test Kit available, which puts together 7 or 8 well characterized combinations of ribbon and label stock. One of them should work for you !!

If you do not find the answer to the question you have check the BAR CODE INDUSTRY FORUM. We'll get you the information you need, or find someone to get it for you.

Or, contact  Circuit Board Label Support for assistance.