PCB Parts Repair Themselves

Tuesday, October 9, 2012 @ 12:10 PM gHale


One of the most important methods of fabricating large printed circuit boards (PCBs) involves the precision electroplating of copper onto the PCB panel immersed in an acidic electrolyte bath.

One of the catches, though, is some of the titanium parts used in the electroplating process suffer substantial wear within a short space of time and replacing these parts generates significant costs.

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There is now a process that enables the damaged components to repair themselves while the PCB fabrication process continues, said a materials science research team at Saarland University.

Atotech, the company that manufactures almost 90 percent of all PCBs used in mobile phones worldwide, is now saving several millions of euros each year as a result. The new patent pending process came from the joint effort by the Saarbrücken research group led by Professor Frank Mücklich and the project group from Atotech.

Electronic components are becoming ever smaller and ever more powerful while at the same time having to connect with one another in increasingly complex ways.

“A printed circuit board today is an extremely complicated three-dimensional structure, that essentially acts like a central nervous system connecting all the various individual components,” said Mücklich, professor of functional materials at Saarland University and director of the Steinbeis Material Engineering Center Saarland (MECS).

The method typically used for high-precision fabrication of large-surface PCBs is acid copper electroplating, in which the PCB panel ends up immersed in an acidic solution of copper ions, the electrolyte. A very high electric current flows through the board transporting copper ions in the electrolyte to the surface of the PCB and into the minute holes, known as vias, into which the leads or contact pins of the electronic components will later be inserted.

“As a result, the PCB is covered with a uniform extremely thin coating of copper whose thickness is less than one tenth of the diameter of a human hair,” Mücklich said.

The PCB panels end up held in the solution by acid-resistant titanium PCB plating clamps that guide the current onto the PCB panel.

“These clamps have to withstand an enormous amount of electrical energy over an area of only a few square millimeters. The extremely powerful current generates sparks that are similar to a lightning discharge and that damage the clamps by eroding their surface each time the panels undergo plating,” said Mücklich, describing the fundamental problem of modern electroplating systems.

The Saarbrücken material scientists examined the damage mechanisms using not only electron microscopy, but also tomographic techniques that allow imaging down to the nano- and even atomic scales.

“We came to realize that with spark temperatures of around several thousands of degrees the previous strategy of trying to develop materials with ever greater resistance to these extremely hot and destructive sparks was not going to prove successful,” Mücklich said.

Even the use of very expensive precious metals, such as platinum, only delays but does not stop the onset of damage. Working together with engineers from Atotech, the material scientists and technologists at Saarland University came up with an extremely economical and reliable solution.

“The new process is similar to the mechanism used to regenerate human skin when wounds heal,” Mücklich said.

The damaged clamps migrate in a circular path within the production facility as if on a carousel. And, like the PCBs that they hold, a new thin layer of copper plates onto them.

“We are essentially creating a recyclable wear layer on the clamps. This has the effect of immediately repairing any damage to the clamp surface and, quite incidentally, also increases the conductivity of the clamps several-fold,” Mücklich said. The new process means there is no longer any need for the complex procedure of removing and replacing the clamps at Atotech’s production facilities. The production process can therefore continue uninterrupted.



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