The Importance of Surface Preparation

Today we are being asked by OEMs, particularly in the high-frequency space, for ways to minimize the amount of surface roughness to provide for enhanced electrical properties. Of course, when you minimize roughness you also run the risk of compromising the optimum adhesion of the smoothed material – especially if you don’t do any surface prep.

Surface preparation is critically important because OEMs want to minimize skin effect, and designers are looking for enhanced electrical properties, especially low loss, low signal loss with that very high frequencies.

If you look at some of the technology trends of today, you’ll find circuitry operating at 77 gigahertz and above, which necessitates a smoother copper surface. Other surface prep benefits include:

• Enhances resist adhesion
• Removes organic/inorganic soils
• Restructures the surface
• Maintain dimensional stability
• Prevents deterioration of copper

And there are a number of ways – both physical and chemical – to prep surfaces, each with their own advantages and disadvantages. They include:

• Brush Scrub
  • Primarily unidirectional
  • Can smear copper, create troughs
• Pumice Scrub
  • Multidirectional
  • Removes less copper than a brush
• Chemical Clean
  • Removes soils/chromates
  • Restructures surface/topography

For the best results, we usually recommend Chemical Clean or a combination of a Pumice Scrub and Chemical Clean. Chemical Clean gives you more control over the surface prep process and allows you to minimize roughness imparted on the copper surface and provides a surface free from organic and inorganic soils.

Pumice is good, especially when compared to a brush scrub, but you need to make sure you use the right kind of pumice – we recommend aluminum oxide or finer. However, this could compromise the optimum adhesion.

We can’t express enough the importance of surface preparation – and chemical surface prep is the key to creating superior electronics products.

Surface preparation issues are troubling, but you don’t have to go it alone. RBP Chemical has the knowledge and resources to help you diagnose any surface preparation issues, and create chemical solutions to address them.