FREQUENTLY ASKED QUESTIONS


1. I have to produce panels with 3/3 and 2/2 mils line and space imaging resolution. Do I need to use collimated or scattered light source ?

2. I hesitate to choose collimated light because this is more sensible to dust. What is your opinion ?

3. What are the advantages and disadvantages of collimated light when working with solder mask ?

4. What is the meaning of molecular diffusion ?

5. When to choose 5 or 8 kW lamp when using collimated light ?

6. What is OptiLight™ light source ?

7. Automatic exposure units are not adapted to the needs of medium or small companies !

8. How do you guarantee an alignment accuracy of ± 10 µm panel to artworks ?

9. What are the advantages of a double sided exposure, compared to a single sided one ?

10. How accurate is optical alignment with 4 CCD compared to the one obtained with 2 CCD cameras ?

11. What are the advantages of both artworks moving while maintaining the panel fix during alignment ?

12. What does "tolerance of positioning ± 12µm" mean ?

13. What is the use of glass artworks ?

14. What is LongLife+ lamp ?

15. What is CMI™, when do I need this function on my exposure unit ?



1. I have to produce panels with 3/3 and 2/2 mils line and space imaging resolution. Do I need to use collimated or scattered light source ?

HDI process requires collimated light in order to reduce light diffusion. Light angle (declination + collimation) with a good collimated light source is typically less than 2° . With scattered light, the angle obtained is between 15° to 25° depending on the machines.

The diffusion value is the distance between the emulsion of artworks and the copper multiple tangent (light angle).

For example, with a dry film thickness (50µm) + Mylar thickness (25µm) = 75µm, the potential diffusion should be :

- 75µm * tan 20°= 27µm with scattered light.
- 75µm * tan 2° = 2.6µm with collimated light

This also shows that thinner dry film causes less diffusion. ALTIX - Automa-Tech™ offers an alternative to collimated or scattered light sources, which is called OptiLight™.

Thanks to better optical characteristics, OptiLight™ brings more than a scattered light unit can, keeping the low running costs of this type of light source. To know more about OptiLight™, see
"What is Optilight™ Source"


2. I hesitate to choose collimated light because this is more sensible to dust. What is your opinion ?

The question you have to answer first is : what kind of line and space you need to manufacture ?

Effectively, the quality of the definition obtained when working with collimated light involves an eventual dust particle to be imaged on the PCB.

Scattered light or OptiLight™ are less sensible to dust, because light diffusion is more important than dust size. This means you won'´t obtain the right value of line and space, with the same diffusion. "You can't have your cake, and eat it".



3. What are the advantages and disadvantages of collimated light when working with solder mask ?

The only disadvantage is exposure time, because solder mask ink needs much more energy than dry film. However, there are solutions :

- Selection of ink : most ink suppliers provide fully qualified solder mask inks requiring energy levels of 250 to 300 mJ/cm².

- Increase intensity : ALTIX - Automa-Tech™ also proposes a high performance collimated light source 8 kW, with more than 50mJ/cm² average intensity for 18"x24" panel size. This means an exposure time of 5 to 6 seconds. There are many advantages to this solution.

On solder mask panels, there may be a gap between the emulsion and the artworks, because of copper thickness deposits on the panel surface. This may cause diffusion, but it is minimal when using collimated light. This phenomenon also occurs in the case of surface irregularities, which can be more evident with multi layers. Due to irregularities of ink deposit less than 2µm in the angle of the conductor and 50µm at some other places, some areas are OVER exposed and other ones are UNDER exposed. Collimated light allows over exposure with less risks of diffusion (less molecular diffusion).



4. What is the meaning of molecular diffusion ?

Molecular diffusion occurs due to the penetration of light into photo sensible materials.

UV light transforms photo polymers. This one reflects one part of UV light. Thicker emulsion involves longer exposure and greater light reflection. Unfortunately this reflection is not only outside, but also inside emulsion. The result is also closely linked to the incidence angle of light.

The molecular diffusion is less sensible with collimated light than with scattered light.



5. When to choose 5 or 8 kW lamp when using collimated light ?

The only resultant difference is exposure time.

If you use a standard dry film, requiring an energy level comprised between 30 and 70mJ/cm², a 5 kW lamp shall suffice. Exposure time will be 2 seconds or less.

If you use ink for primary image or solder mask with minimum required energy level of 250mJ/cm², it may be recommended to work with a 8 kW lamp ; otherwise the exposure time may be excessive.



6. What is OptiLight™ light source ?

OptiLight™ is a new light source developed by ALTIX - Automa-Tech™ to replace Scattered Light units. This new source has been designed in order to increase precision and resolution, keeping the advantages of classical scattered light source, such as a cheaper running cost compared to collimated light.

The OptiLight™ lamp source due to its unique design is an evolution of our scattered light unit using a new type of lamp, which is an exclusivity of ALTIX - Automa-Tech™, with a shorter arc length and a new design of the optical path.

Collimation improved by 50%
Light uniformity improved by 25%
Efficiency improved by 60%

Collimation¹
Efficiency(21"x25")
Light uniformity
Declination²
Scattered
± 20°
57 mW/cm²
± 13 %
17°
OptiLight™
± 10°
90 mW/cm²
± 10%
15°
1, 2 : Those data are max. collimation / declination obtained in both X & Y directions.


This new light engine can be installed on ACURA and Reel-to-Reel family products ; but it can also be retrofitted in old scattered light imaging machine. To learn more about the performances and how to upgrade an old unit from scattered to OptiLight™ light source, see "OptiLight™
brochure"


7. Automatic exposure units are not adapted to the needs of medium or small companies !

It is difficult to calculate the cost for everyone, because each case is different ; but the main advantages are as follows :

- Repeatability of quality due to the process automatisation

- The best possible artworks alignment, thanks to the use of optical process.

- The very fast set up. With an automatic machine, the total set up time is less than 2 minutes (when the set of artworks is ready close the machine). The average time with a manual machine is 8 minutes. You save 6 minutes per batch, and so 7 hours of daily production if you manufacture 50 batches per day !

- You get an automatic production report per batch.

- And so on...


8. How do you guarantee an alignment accuracy of ±10 µm panel to artworks ?

All of the machine performances are listed by the "Event Logging System".

All kinds of data are recorded for every panels (positioning before video alignment, result after video alignment, value after vacuum, energy on every side, glasses temperature before and after exposure, and so on...).

The "Event Logging System" allows every panels to be easily controlled : data per panel, average per batch, trend, and so on... These results may be downloaded to any standard format. Our system can also be connected to any PC, for an easy access to data.



9. What are the advantages of a double sided exposure, compared to a single sided one ?

The advantages are not the same, if you work with inner layers, external layers, solder mask, build up or conformal mask. Here are the one common to all processes :


- Automatic control of the dimension of upper artworks, in regards to the lower one, with possibility of stopping exposure if both dimensions are out of tolerance.

- Exposure of both sides with the same conditions.

- No possibility to reverse artworks ; the system controls assures that the upper artwork is installed on the upper glass and that the lower artwork is on the lower one.

- Smaller footprint for double sided exposure.

- Very small set up time : less than 2 minutes for both sides. For Inner layers, it is the only way to guarantee the positioning of the image Top-to-Bottom Laser Via holes. It is the only system to simultaneously compensate laser drills on both sides, mechanical holes and reduce the "Pisa effect" for double sided build up.




10. How accurate is optical alignment with 4 CCD compared to the one obtained with 2 CCD cameras ?

If all of the distorsion were linear, the mathematical alignment result should be the same. But, in PCB activity, the distorsion of base materials is not linear (due to surface preparation, brushing, humidity, drying, drilling dispersion,...).

A better average of all distorsion is attained by considering 4 targets one in each corner of the panel. In these conditions, the alignment with 4 CCD cameras is always better than the one obtained with 2 CCD cameras, but this is directly linked to the distorsion of base materials, and drilling dispersion.

Before choosing 4 or 2 CCD cameras you need to consider the panel size (larger panels require 4 CCD cameras) and the class difficulty of the product (the choice is not the same if you produce HDI product 2/2 mils L/S resolution or standard product 5/5 mils L/S resolution). Typically, more difficult or tighter tolerance jobs will require 4-point (4 CCD cameras) alignment.



11. What are the advantages of both artworks moving while maintaining the panel fix during alignment ?

ALTIX - Automa-Tech™ employs a patented process for aligning top and bottom artworks by moving these while maintaining the panel fixed. Conventional systems move the upper artwork and also move the panel. This latter method is less attractive since moving the panel requires :

- Drilling 2 holes in the panels and placing pins in these holes. This causes a pollution due to particles from the holes falling in the exposure area.

- Additional problems may arise when holes are completely or partially covered with dry film.

- The pins that are used to move panels are small flexible mechanical parts exhibiting spring effect which is not possible to suppress, resulting in reduced positioning accuracy..


12. What does "tolerance of positioning ± 12µm" mean ?

Positioning tolerance is the performance of the machine to align perfect artworks and panels. The process is as follows :

- The system compares the position for every target of artworks and panels, by computing the error components in X-axis (dx) and Y-axis (dy) for each of them

- Afterwards, the barycenter of all targets are compared to get the origin dx=0, dy=0 in the center of panels.

- The result is for 2 targets systems and not for dx and dy of the right target = -dx ,-dy (±12µm) If artworks are 100µm bigger than the panel, the result on the panel near the target is not ±12µm, but 50 ±12 µm.

13. What is the use of glass artworks ?

The only advantage is the stability of the mask with respect to temperature and humidity variations. The standard Mylar artwork is very sensible to humidity and temperature, for example

- Temperature effect 16µm/°C/m with very small hysteresis effect.
- Humidity effect 8µm/%RH/m with important hysteresis effect. For example if your artworks are manufactured and stabilized in a room at 20°C and 45% RH and you use them at 24°C, 53%RH, for a 700mm artwork the possible distorsion will be :

((24-20)*16+(53-45)*8)*0.7 = 128µm.

Glass artworks are less sensible to temperature, and humidity has no effect.

- Temperature effect is 4µm/°C/m The resulting effect for the same dimensions is : ((24-20)*4+(53-45)*0)*0.7 = 16µm.

This is the main reason to use glass artworks. On the other hand, the price of glass artworks is much higher. In most cases, working in a stable clean room, with good exposure units controlling glass temperature as the ones provided by ALTIX - Automa-Tech™, provides a good solution and prevents from using expensive glass artworks. .

14. What is LongLife+ lamp ?

EZL073 Long Life+ lamp is a 5kW short arc lamp developed by ALTIX - Automa-Tech™ and USHIO which can be installed in any 5kW collimated light exposure unit.

Its main advantage compared to other types of short arc lamps is its guaranteed lifetime ; 1500 hours instead of 800 hours for standard ones.

This brings important savings to ALTIX - Automa-Tech™'s customers because this lamp costs only 12% more while it lasts 90% more than a classical lamp.

ALTIX - Automa-Tech™ can propose, free of charge, the modification of the lamp socket of your current units to fit this new Long Life+ lamp. For more information see "Long Life+ lamp brochure"

Call us !

We can make the cost calculation of your savings with you.



15. What is CMI™ ? When do I need this function on my exposure unit ?

This new patented system allows a perfect contact between the artwork photo-emulsion and the printed circuit board surface resulting in a very high resolution down to 15 µm (0.6 mils).

This new feature is especially dedicated to outerlayers & soldermask applications with uneven topographic surfaces. It has been developed to avoid all the classical imaging troubles due to off-contact between printed circuit boards and glasses on which the artworks are sucked to.
IMAGING WITH US!