Plasma Etch Electrical Case Studies

Plasma Etch Printed Circuit Boards

CASE STUDY #1
Parts: Printed Circuit Boards
Contaminates: Bromine Based Epoxy Smeared On Inner Layer Copper Interconnects
Industry: Printed Circuit Board
Equipment Used: Plasma Etch model Mk-II

Details of application:
This company is a defense contractor to the U.S. Government. They need to remove the drill smear from the through hole interconnects in the printed circuit board. The military requires a three point connection on the inner layer interconnects. This plasma process is etchback. This process produces a 5 to 6 tenth of a mil removal of epoxy in the through hole. The through hole interconnects must be free of epoxy smear to allow good electrical contact between the inner layer and surface copper.

This company uses a combination of Carbon Tetrafluoro-Methane and Oxygen plasma to etchback the throughholes in their printed circuit boards.
This company chose Plasma Etch based on several advantages our company offers. Process temperature control is the single most important parameter in the plasma process. Temperature has primary control over etch rate and a secondary effect on etch uniformity and repeatability, the process temperature must be regulated throughout the entire plasma sequence. Our process temperature is regulated by the patented electrode temperature control system. No other plasma offers non-plasma generated chamber heating.

The plasma process generates high energy plasma fields at the edge of the electrodes, which causes accelerated etching at these edges. The overall effect is higher etch rates at the electrode edges; with a gradual reduction in the etch rate as it approaches the center of the electrode. This can be viewed as the bull's eye effect that results in severe process non-uniformity. All vacuum chamber internal surfaces on Plasma Etch's systems are electro statically shielded to eliminate plasma reactions with the chamber walls. Plasma activity is then uniform across the electrode surface. This creates a uniform etch across the entire surface.
Plasma Etch utilizes high frequency RF power (13.57 MHz) to maximize processing rates and production throughput. The physics of a high frequency RF plasma is very different from a low frequency RF plasma. The high frequency generates a much more reactive plasma. The high frequency plasma is isotropic (etch uniformly in all directions). This feature is required for processing three dimensional objects or small drilled holes. Additionally, systems that operate at 13.57 MHz are three times as fast as systems that operate at 40 KHz.

Plasma Etch Polyimide Circuit Boards

CASE STUDY #2
Parts:Polyimide Circuit Boards
Contaminates:Hydrocarbons, Epoxy, Insulator Residue
Industry:Polyimide Circuit Board
Equipment Used: Plasma Etch model Mk-II

Details of application:
This company manufactures multi-layer polyimide circuit boards. The company needed to military etch the epoxy to make a three point connection with the copper inner layer inner connects. The plasma process will produce a 5 to 6 tenth of a mil removal of polyimide in the drilled through hole. The throughhole inner connects must be free of polyimide drill smear to allow good electrical contact between the plated hole wall and the inner layer inner connects.

The company uses a 50/50 ratio of Carbon Tetrafluoro-Methane and Oxygen plasma to etchback the throughholes in their circuit boards. This plasma reduces process time to approximately 30 minutes for desired results. Using a high frequency RF generator reduces the cycle time.

Plasma Etch Teflon® Multi-Layer Circuit Boards

CASE STUDY #3
Parts:Teflon® Multi-Layer Circuit Boards
Contaminates: Hydrocarbons
Industry: Teflon® Multi-Layer Circuit Board
Equipment Used: Plasma Etch model PE-100

Details of application:
This company is a producer of Teflon® multi-layer boards. They use isotropic plasma to activate the Teflon® surface in the drilled hole prior to electroless copper plating.

This company uses a dual sequence plasma for their surface activation. The first is a 50/50 Carbon Tetrafluoro-Methane and Oxygen plasma for 15 minutes. With a high frequency generated plasma, no post Oxygen cycle is required for ash removal. Excellent plating results have also been obtained using a 15 minute Hydrogen Gas cycle.

Plasma Etch Multi-Layer Circuit Boards

CASE STUDY #4
Parts: Multi-Layer Circuit Boards
Contaminates: Hydrocarbons
Industry: Multi-Layer Circuit Board
Equipment Used: Plasma Etch model Mk-III

Details of application:
This leading manufacturer of printed circuit boards uses plasma to form .003 mil micro via holes in their circuit boards. The plasma used is a directional, Reactive Ion Etch (RIE). The company uses a print and etch process to open the copper, then the Reactive Ion Etch forms the micro via.

Plasma Etch is the first plasma manufacturer to develop multiple level RIE and use plasma for micro via formation. This project was done in cooperation with Hadco Phoenix. Plasma Etch offers eight and sixteen level RIE systems.
Reactive Ion Microvia formation is very cost competitive to laser drilling.