The intention of publications made by Atotech is to share the results of our extensive research and development on a non commercial basis. With these presentations we aim to provide in-depth process information and inform about the latest investigations and results in each technology field. It should enable the reader to gain a complete and comprehensive understanding of our process solution and of general phenomena encountered in the electroplating industry.

This segment presents the recent papers from the business technology team panel and pattern plating.

Increased Miniaturization with Trench Filling Technology
Dr. Bernd Roelfs, Atotech Germany, Toshiya Fujiwara, Atotech Japan K.K., May 2007

This paper presents a system for the production of structures based on the filling of trenches with minimum surface plated copper on a dielectric substrate. The trenches with line and space dimension below 15 µm can be produced by methods such as laser ablation and subsequent metallisation processes are used to complete the circuitisation.

Download complete paper here: pdf file (File size 445 kB)

Super High Density Two Metal Layer Ultra-Thin Organic Substrates for Next Generation System-On-Package (SOP), SIP and Ultra-Fine Pitch Flip-Chip Packages
Venky Sundaram, Hunter Chan, Fuhan Liu, Rao Tummala, Microsystems Packaging Research Center, Hugh Roberts, Atotech USA, Sven Lamprecht, Kai Matejat, Akif Oezkoek, Atotech Deutschland, Scott Kennedy, John Dobrick, Dirk Baars, Rogers Corporation, February 2009

This research includes use of a state-of-the-art electroless and electrolytic copper plating process to achieve the required ultra fine line circuitry and through-via filling. These processes have been optimized on next-generation dielectrics characterized by ultra-low loss, low dielectric constant, low CTE and low moisture uptake with stable properties up to 40GHz.

Download complete paper here: pdf file (File size 610 kB)

Theoretical and Practical Aspects of Thermo Mechanical Reliability in Printed Circuit Boards with Copper Plated Through Holes
Stefan Neumann, Nina Dambrowsky, Stephen Kenny Atotech Deutschland GmbH, Germany, September 2009

The thermo mechanical reliability of copper plated through holes (PTH) in printed circuit boards is normally determined by different tests e.g. thermo cycle test (TCT), interconnect stress test (IST) or highly accelerated thermal shock (HATS).
During these tests the plated copper is exposed to stresses and strains which are below the tensile strength and the fracture strain, respectively, which leads to a strength-dependent fatigue failure mechanism. To save time, as the duration of the above mentioned tests can vary between one day and several weeks, a knowledge of the functional relationship of the determining factors for the cycles to failure can be very helpful as it can provide the possibility to compute the dependency of the PTH copper reliability on different variables.
This paper introduces an extension to analytical considerations to estimate the influence of various parameters (e.g. coefficient of thermal expansion, temperature range, through hole diameter, thickness of PCB, thickness of plated copper) on the fatigue life of PTH copper during thermal excursion as published by Werner Engelmaier in [1]. The impact of in particular the glass transition temperature of the based material and also the final finish of the plated circuit board are also discussed.

Download complete paper here: pdf file (File size 350 kB)

Electrolytic Solder Deposit for the Next Generation Solder Resist Openings and Bump Pitch
Kai Matejat, Stephen Kenny, Sven Lamprecht, Atotech Germany, Tashiya Fujiwara, Atotech Japan, June 2009

Current methods for the formation of pre-solder bumps for board to board solder joints and in particular for flip chip attachment use stencil printing techniques as part of the process utilising a suitable solder paste. The continuing trend towards increasing miniaturisation and the associated decrease in size of solder resist opening, SRO is causing production difficulties with the stencil printing process. Practical experience of production yields has shown that stencil printing will not be able to meet the requirements for solder bump pitch production below 0.15 mm for IC substrate applications and also 0.3 mm bump pitch for HDI applications.

This paper describes a novel approach to replace the stencil printing process by use of an electrolytic deposition of solder. In contrast to stencil printing, use of electrolytic deposition techniques allows production of solder bumps with a pitch below 0.15 mm and with a SRO below 80 µm.
The process steps required for electrolytic deposition of solder bumps are shown together with the necessary pre-treatment, this includes metallisation techniques to enable uniform solder deposition over the bump array.
The advantages of replacement of stencil printing by electrolytic solder deposition are shown and in particular the improvement of bump reliability and the potential to significantly decrease costs by yield improvement.

Download complete paper here: pdf file (File size 110 kB)

Through Hole Filling Production for IC Substrates and HDI Applications
Dr. Bernd Roelfs, Atotech Germany, Tashiya Fujiwara, Atotech Japan, June 2008

This paper describes a through hole filling process with Cu by electroplating in contrast to conventional use of an appropriate resin to plug through holes followed by further processing with metallization and circuitization. It demonstrates recent progress in filling through holes and discusses its current limitations.

Download complete paper here: pdf file (File size 85 kB)

Via filling applications for IC Substrate and in particular Flip Chip BGA
Dave Baron, Holger Schulz, Bernd Roelfs, Atotech Germany, February 2008

BMVs for IC Substrate fabrication are Cu plated and usually completely filled to improve the reliability of connections between different Cu layers compared to the traditional conformal plating. However this technique has limitations like short life time of electrolytes, surface distribution of plated Cu inferior to inert anode systems and limitations in filling performance if the plated Cu thickness is below 15 μm. This report describes the progress in the plating technology to meet future and current demands from a process technology point of view. It also presents a new production technology by using embedded conductors based on the improved Via filling technology.

Download complete paper here: pdf file (File size 380 kB)

Online-TCT: New Measurement Technique for Precise Results at Accelerated Lifetime Tests for PCBs
Dr. Stefan Gerhold, Stefan Neumann, Detlev Nitsche, Prof. Dr. Nasser Kanani, Atotech Deutschland GmbH, Germany, Axel Ballon, Automatisierungstechnik Voigt GmbH, Germany, March 2004

BMVs for IC Substrate fabrication are Cu plated and usually completely filled to improve the reliability of connections between different Cu layers compared to the traditional conformal plating. However this technique has limitations like short life time of electrolytes, surface distribution of plated Cu inferior to inert anode systems and limitations in filling performance if the plated Cu thickness is below 15 μm. This report describes the progress in the plating technology to meet future and current demands from a process technology point of view. It also presents a new production technology by using embedded conductors based on the improved Via filling technology.

Download complete paper here: pdf file (File size 350 kB)

New Concepts for the Production of HDI Printed Circuit Boards
Stephen Kenny, Atotech Deutschland GmbH, Germany, March 2006

This paper presents developments in copper plating process and equipment to ensure best possible quality and production yield in HDI production for hand held devices and for IC substrate technology. It describes the use of insoluble anodes as one of the main factors in the improvement in production quality together with the associated copper plating electrolyte. The advantages and disadvantages in panel and also pattern plating systems are presented and discussed together with combined solutions for blind micro via copper filling and also through via copper filling.

Download complete paper here: pdf file (File size 360 kB)

Fine Line Technology and Panel Plating - Opposing Directions, One Solution
Stephen Kenny, Atotech Deutschland GmbH, Germany, June 2007

The standard method to achieve the increasing requirements for high density interconnects (fine lines and spaces) is by using a variation of pattern plate copper metallisation, however this technique suffers from the well known variation in surface distribution. The technique of panel plate copper metallisation offers the advantage of best possible surface distribution over the whole surface, but with the critical disadvantage, that the needed thickness of copper to achieve blind micro via filling cannot be etched to give the required line and space tolerances.

This paper presents latest results with the Uniplate InPulse 2 horizontal copper plating system which combines excellent surface distribution together with a novel panel plate metallisation which ensures filled blind micro vias with minimum surface plated copper.

Download complete paper here: pdf file (File size 240 kB)

Blind Micro Via Filling in Conveyorised Equipment
Stephen Kenny, Bert Reents, Dr Bernd Roelfs, Atotech Deutschland GmbH, Germany, January 2006

In this paper the advantages of a conveyorised system (horizontal and vertical) for the continuous production of filled blind micro vias are shown as also the benefits of an insoluble anode system. The extension of blind micro via filling to the filling of plated through holes is discussed and development results are shown using the Uniplate Inpulse to fill through holes with electrolytic copper plating.

Download complete paper here: pdf file (File size 400 kB)

Filling Micro Vias Theoretical and Practical Aspects
Bert Reents, Stephen Kenny, Atotech Deutschland GmbH, Germany, March 2002

The dimensions of through and blind micro vias have reached a limit where, due to various reasons, the filling of these cavities becomes a necessity. In the paper presented the influence of the major variables for the filling capability, ranging from organic and inorganic additives to pulse parameters are being explained. Examples from horizontal and vertical production lines are shown and optimum via geometry considerations will be discussed.

Download complete paper here: pdf file (File size 390 kB)

New Plating Technology for Blind Micro Via Filling and Through Hole Filling
Bert Reents, Stephen Kenny, Atotech Deutschland GmbH, Germany, March 2005

This paper discusses the limiting factors in the acid copper electrolyte lifetime currently in production for BMV filling and how this can be overcome in a system using insoluble anodes.

Examples of current production equipment and the via filling results achieved are shown from horizontal equipment as well as with conventional vertical and also vertical conveyorised equipment all using insoluble anode technology. The extension of blind micro via copper filling to the electrolytic copper filling of plated through holes is discussed and development results are shown using the insoluble anode system.

Download complete paper here: pdf file (File size 290 kB)

The Influence of Fluid Dynamics on Plating Electrolyte for the Successful Production of Blind Micro Vias:
Laboratory Investigations Leading to Optimised Production Equipment
Bert Reents, Stephen Kenny, Atotech Deutschland GmbH, Germany, March 2002

Successful copper plating of blind microvias is very strongly dependant on the effective mass transport of copper ions into the vias. This paper describes the methods used to evaluate solution flow in micro vias carried out in controlled laboratory conditions. The subsequent successful implementation of improved solution flow in full scale horizontal and also vertical production is shown, in both cases using production equipment operating with reverse pulse plating and insoluble dimensionally stable anodes.

Download complete paper here: pdf file (File size 560 kB)

Blind Micro Via and Through Hole Filling in Horizontal Conveyorised Production System
Stephen Kenny, Atotech Deutschland GmbH, Germany, Mike Palazzola, Atotech USA Inc., March 2009

This paper presents a novel electrolytic copper panel plate system incorporating equipment and specially developed electrolyte which enables filling of blind micro vias with a minimum of surface plated copper. Development results showing capability of the used Uniplate InPulse2 system also for through hole filling of substrates is shown together with discussion of possible application areas for this new technology.

Download complete paper here: pdf file (File size 215 kB)

CAP - A New Plating Sequence for Advanced Via Filling and Through Hole Plating
Ingo Ewert, Dr. Bernd Roelfs, Atotech Deutschland GmbH, Germany, June 2006

A new process sequence for BMV filling is presented in this paper. This CAP process (Conditioning, Activation and Plating) is a synergistic procession combining pre-treatment and plating, its performance is superior to standard process in terms of filling ability and electrolyte lifetime. The process can be adopted in standard plating lines operating with soluble and inert anodes and also with pattern and panel plating systems.

Download complete paper here: pdf file (File size 215 kB)

New Plating Technology for Blind Micro Via Filling and Through Hole Filling
Stephen Kenny, Bert Reents, Atotech Deutschland GmbH, Germany, June 2005

Blind micro via filling technology is used in the chip carrier and packaging industry particularly for the production of stacked vias, however there are limiting factors in the acid copper electrolyte lifetime.

This paper presents examples of current production equipment and the via filling results achieved with horizontal as well as with conventional vertical and also vertical conveyorised equipment and how to elongate the electrolyte lifetime with an insoluble anode system.

Download complete paper here: pdf file (File size 290 kB)

Flexible PCB Plating: Through Hole Considerations from Pretreatment to Plating, Experience and Solutions
Dr. Gerd Linka, Stephen Kenny, Bert Reents, Atotech Deutschland GmbH, Germany, April 2005

This paper gives an insight into the current status of flex / flex-rigid manufacturing along with suitable examples from the point of view of PTH processing and also electrolytic copper plating.

Suitable solutions to common manufacturing issues are given in particular addressing the critical factors in handling thin core material. New developments in processing are shown together with the benefits realised in particular the electrolytic through hole filling of thin core material.

Download complete paper here: pdf file (File size 330 kB)

Acid Copper Plating with Insoluble Anodes - A Novel Technology in PCB Manufacturing
Dr. Jürgen Barthelmes, Atotech Deutschland GmbH, Germany, September 1999

In the paper presented the basic electrochemical equations of different electrolyte alternatives for the plating of PCBs with insoluble anodes is shown and the advantages and disadvantages of these systems is explained.

A general understanding of the meaning of anode potentials, the interpretation of potential current functions, the development of the ferrous ion concentration (in the Atotech electrolyte) with time and current density and the interaction of organic additives with the new substrate is discussed.

Download complete paper here: pdf file (File size 390 kB)

New Concepts for Production of High Aspect Ratio Printed Circuit Boards
Stephen Kenny, Bert Reents, Atotech Deutschland GmbH, Germany, J. Zosel, Kurt-Schwabe-Institut, Germany, March 2003

One of the limiting factors in copper deposition with high aspect ratio PCBs is the mass transport of ions into the high aspect ratio holes.

This paper presents the results of the investigations of the electrolyte exchange mechanism and also the influencing factors particularly in high aspect ratio holes. An adequate electrolyte agitation and the advantages of a pulse plating system using higher current densities to give improved surface distribution and throwing power in the through holes is described.

Download complete paper here: pdf file (File size 220 kB)

HDI Production using Pulse Plating with Insoluble Anodes
Stephen Kenny, Kai Matejat, Atotech Deutschland GmbH, Germany, October 2000

The paper presents a production system incorporating reverse pulse plating of an acid copper electrolyte with dimensionally stable anodes.

Through the use of insoluble anodes constant production conditions are achieved in the plating cell, giving improvements in productivity and quality. The desired result is constant without the need for time consuming anode maintenance. The Optipulse in situ measurement system for fine tuning of the InPulse process is introduced and the correlation between the pulse wave form, which is determined directly on the panel surface, and the copper crystal structure is shown.

Download complete paper here: pdf file (File size 540 kB)