Printed Circuit Design & Fab - June 2008 - (Page 41)

! light being used, ing solutions in as any transparboth mechaniency or reflection cal and in laser will not allow the microvia drilllight to couple ing technology FiGurE 2. 30, 40 and 50 micron diameter vias in resin coated FiGurE 3. Oblique into the material. are constantly copper. view of UV drilled via. Lasers can being developed. be used for many other applications Many of the advancements in the field mm to 0.100 mm. FiGurE 2 shows a row other than drilling vias. These include of laser microvia drilling include extendof UV laser drilled vias in resin coated dielectric material removal for contact ing the capabilities of CO2 lasers to copper, at 30, 40 and 50 microns diampoints, solder mask removal, the drilling eter, respectively. FiGurE 3 is an oblique drill smaller microvias, and increasing of other materials such as alumina, metproduction throughput by using multiple angle of a UV laser drilled hole in resin, als, etc. The flexibility of lasers makes laser beams using both UV lasers and showing the clean entrance and surface. them extremely useful, especially for CO2 lasers. In addition to the requirement of small lot runs. FiGurE 4 shows a solder picking the correct drilling technique One of the highest throughput sysaccording to desired via diameter, there tems is the LU-G series UV laser drilling mask removal application. The left side are also material compatibility issues that system with a four beam configurashows a customer’s attempt to mechanimust be addressed. Mechanical drills will tion, two beams per galvanometer. With cally remove the solder mask using a usually drill any material, but lasers are drilling rates of 2000 holes/second in Dremel tool, while the right side shows limited in the materials that they can direct resin, the system is a world-class CO2 laser removal of the mask. FiGurE 5 drill. For instance, CO2 lasers cannot production tool within the high density shows a dense array of 100-micron holes microvia marketplace. The system can directly drill copper, so UV lasers are in 200-microns thick alumina. manufacture microvias with diameters used for this material, although Hitachi In conclusion, while there have been as small as 0.020 mm. Designed to prohas pioneered the ‘drilling’ of very thin no recent major technological breakduce precision microvias, the system is copper by enhancing absorption on the throughs in the drilling of vias, there have outfitted with field tested and proven surface with a sacrificial layer. Normally been quite a few engineering advances beam shaping technology. Beam shapcopper is highly reflective for 10-micron that have increased throughput, enabled ing is used to form a flat top laser wavelength light, but if a surface altering drilling smaller via sizes and increased beam intensity at the target image plane layer is applied to the copper that allows drill reliability in the field. For the forefor increased control of wall taper and adsorption, the thin copper can be drilled seeable future, both mechanical and laser roundness, enhancing the quality of the by the thermal overload. CO2 lasers are drilling will continue to be used as commicrovias produced. plementary processes, with the choice of also very useful for dielectrics, as the Recently, four panel CO2 laser drilltechniques depending on many of the drill rate of CO2 lasers is typically much factors discussed above. pcd&f ing systems have been manufactured higher than UV lasers. Also, glass embedthat incorporate multi-panel and multided or non-homogeneous materials are beam technology, increasing production usually best drilled with the CO2 laser. GaBor kardoS and ronald SchaEFcapability by nearly 190%. The CO2 One interesting feature of the CO2 laser FEr are with PhotoMachining, Inc. They is that since copper reflects the laser light, laser systems can be applied to either can be reached at gkardos@photomachining.com and rschaeffer@photomait is a self-limiting process when drilling direct drilling applications of dielectric, chining.com, respectively. todd liZottE through dielectric and down to a layer of or to both copper patterning and dielecis Us Director of emerging Technology copper. In the case of a UV laser, much tric removal. In general, UV technology for Hitachi Via Mechanics, Londonderry, more care must be taken to assure that targets vias 0.050 mm or less for direct NH and can be reached at todd.lizotte@ the bottom copper layer is not blown resin drilling and Cu exposure, while hitachi-via-usa.com. ! right through. A fundamental considerCO2 lasers occupy the ‘middle ground’ ation for drilling any material is that the between mechanical and UV drilling, material must absorb the wavelength of used in drilling applications from 0.050 FiGurE 4. solder mask removal – mechanical and CO2 laser. JUNE 2008 FiGurE 5. 100 micron diameter vias in 200-micron thick alumina. ! printEd circuit dESign & fAB 41

Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - June 2008

Printed Circuit Design & Fab - June 2008 Contents Our Line Market Watch Around the World Happenings ROI Tip Jar Interconnect Strategies Final Finish Forum DFA/DFT Signal Integrity From the Field DFA Fab Basics Drill Off the Shelf Marketplace Ad Index BGA Bulletin

Printed Circuit Design & Fab - June 2008

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