Electronics Assembly Knowledge, Vision & Wisdom
Electroplated Copper Filling of Through Holes
Electroplated Copper Filling of Through Holes
This paper discusses a through hole copper filling process for applications of high density interconnects and IC substrates.
Production Floor

Production Floor programs cover topics including:
CAD/CAM/CIM/EDA, Circuit Board Handling, Clean Room, Cleaning Operations, Component Insertion, Component Prep, Dispensing, Feeders, Fume Extraction, Hand Tools, Labeling/Marking, Lasers, Material Handling, Odd Form, Ovens/Curing, Packaging, Stencil Printing, Repair/Rework, Soldering and more.
Submit A Comment
Comments are reviewed prior to posting. You must include your full name to have your comments posted. We will not post your email address.

Your Name


Your Company


Your E-mail


Your Country


Your Comment



Authored By:
Kesheng Feng, Bill DeCesare, Jim Watkowski
MacDermid, Waterbury, CT

Mike Yu
MacDermid Taiwan Technical Center

Don DeSalvo
MacDermid Suzhou Technical Center

Summary
This paper discusses a through hole copper filling process for application to high density interconnects constructions and IC substrates. The process consists two acid copper plating cycles. The first cycle uses periodic pulse reverse electroplating to form a bridge in the middle of the hole, followed by direct current electroplating to fill the resultant vias formed during the bridge cycle. This process can provide defect-free filled holes with total plated copper on the surface below 25 um, with dimple less than 5 um for boards with core thickness of 0.2 mm and 0.25 mm. This process was designed to be deployed in specially constructed vertical continuous platers (VCP), thus reducing capital equipment compared to horizontal conveyorized electroplaters.

The chemical components, copper, acid and additive, for periodic pulse reverse plating cycle, are optimized via experimental conditions selected from DOE (design of experiments) software. Critical parameters are identified and the impact on cavity formation during the bridging step is quantified. The additive and copper concentrations play key roles in reducing defects during bridge formation and on the resultant via formation.

A high performance via-filling process is used to fill the formed vias, with less than 5 micron dimple depth, while depositing approximately 12 microns on the surface. The thin surface copper enables fine line resolution without the need for planarization or grinding. The mechanical properties of the plated deposit meet or exceed all IPC standards.

This process is applicable to both laser-drilled X shape through holes and mechanically drilled straight holes. Laser-drilled through holes are bridged faster than mechanically drilled holes. However, mechanically drilled holes show a lower tendency for drilling induced defects, especially at the smaller hole diameters of 0.1mm. This process has shown capability to fill through-holes in thicker cores of 0.4 mm to 0.8 mm, where further investigation continues.

Conclusions
A through-hole copper filling technology for application to high density interconnect constructions and IC substrates was demonstrated. The process consists of two acid copper plating cycles. The first cycle is periodic pulse reverse electroplating to form a bridge in the middle of the hole, followed by direct current electroplating to fill the resultant double vias formed during the bridge cycle. This process can provide defect-free filled through hole with solid copper. The mechanical properties of the plated deposit meet or exceed all IPC standards.

Initially Published in the IPC Proceedings

Comments
No comments have been submitted to date.
Free Newsletter Subscription
Every issue of the Circuit Insight email newsletter will bring you the latest information on the issues affecting you and your company.

Insert Your Email Address

Directory Search


Program Search
Related Programs
bullet Dielectrics for Embedding Active and Passive Components
bullet Design and Fabrication of Ultra-Thin Flexible Substrate
bullet Circuit Material Performance for PCBs at Millimeter Wave Frequencies
bullet NASA DOD Phase 2: Copper Dissolution Testing
bullet Optimizing Insulated Metal Substrate Application
bullet HDI Structures Using Thin Films and Low Temp Paste
bullet Manufacture of Aluminum Substrate PCBs
bullet Electroplated Copper Filling of Through Holes
bullet High Reliability, Stress-free Copper Deposit
bullet Examination of Glass-fiber and Epoxy Interface Degradation in Circuit Boards
More Related Programs