Electroplated Copper Filling of Through-holes: Influence on Hole Geometry


Reading time ( words)

Abstract

This paper discusses a through-hole copper filling process for application in high-density interconnect constructions on thin IC and LED substrates where high reliability and thermal management are essential. The process consists of a two-step acid copper plating cycle. The first step utilizes periodic pulse reverse (PPR) electroplating to form a conductive copper bridge across the middle of a through-hole and is followed by direct current electroplating to fill the resultant vias formed in the bridge cycle.

The ability of the process to fill a variety of through-hole sizes on substrates of varying thickness while minimizing the overall surface copper build-up are critical in applications requiring efficient thermal management as circuit miniaturization continues.

The through-hole fill technology and factors that affect its performance such as substrate thickness and through-hole diameter will be presented in this paper.

Introduction

Resin or paste plugging of through-holes in cores has been a part of build-up technology, especially in IC substrate construction, for many years. Technological advances encompassing increased circuit density and stacked via construction, coupled with higher power devices, have added an extra dimension of thermal management where a copper filled through-hole becomes advantageous (Figure 1).

Advantages of copper filled through-holes include:

  • Reduction in CTE mismatch of resin/paste plug
  • Stable platform for stacking microvias
  • Solid pillar structure within through-hole
  • Lower likelihood of adhesion failure on the plated-over filled via
  • High thermal conductivity of copper

New technologies were developed to completely fill through-holes and vias in build-up core layers in HDI and IC substrates with solid copper. Among the approaches for filling through-holes in a thin core board with copper was DC plating.

To read this article which appeared in the January 2017 issue of The PCB Magazine, click here.

Share


Suggested Items

Unimicron Germany Rises from the Ashes with New Smart Factory

04/30/2018 | Pete Starkey, I-Connect007 and Michael Weinhold, EIPC
This is a review of the grand opening of Unimicron’s new smart factory in Geldern, Germany. A fire in a PCB shop is an experience we all dread, but still it happens, and the consequences can be devastating. In the early hours of December 28, 2016, the innerlayer production plant at RUWEL International in Geldern, Germany, caught fire and the whole factory and its contents were destroyed.

Elga Europe Reality and Ultra-High-Resolution Photoresist

04/24/2018 | Patty Goldman, I-Connect007
While walking around the PCB hall at productronica, I was approached by my good friend Gene Weiner. Gene emphatically directed me to the Elga booth to find out about their new extra-thick dry film that can image extremely fine features with a perfectly perpendicular sidewall. Elga Europe CEO Giorgio Favini filled me in on the details.

The Vast Offerings in Laminate Technologies from TUC

04/10/2018 | Patty Goldman, I-Connect007
While at IPC APEX EXPO a few weeks ago, I sat down with George Hsin, chief strategy officer for TUC Worldwide, and Alan Cochrane, president of TUC North America. I was interested in learning more about the company and their laminate products and Alan was happy to fill me in.



Copyright © 2018 I-Connect007. All rights reserved.