Plasma vs. Permanganate

Plasma

One plasma treatment system with a small footprint

Permanganate

A series of tanks for etching and rinsing. Much larger footprint

Equipment

Plasma Advantages

Plasma

Environmentally benign.

Permanganate

Require hazardous waste disposal process.

Environmental impact

Plasma Advantages

Plasma vs. Permanganate

– Plasma• Can perform high-aspect ratio specifications• Processes can be complementary• Environmentally friendly (no waste)• Monitoring of critical process parameters

– Permanganate• Does not flow well in small vias found in multi-layer PCBs

(very high layer count)• Does not well clean the very small via holes usually

found at the inner layer level (laser-drilled via holes)• Acid etching is difficult to etch polyimide dielectrics

Plasma Advantages

Plasma Advantages

PlasmaPlasma has the flexibility to adjust process parameters for

desmearing small diameter holes in thick panels. Lowering the

pressure and increasing the gas flow create a ion direction to

the center of the hole. Hole sizes down to 0.004” @ 44:1

aspect ratio have been successful

PermanganateAs the via size decreases the ability for success in a wet

process is reduced. Liquid flow is restricted causing air

bubbles. These areas will not yield resin smear removal.

Backplane boards or boards .250 in. thick with 8:1 aspect ratio or higher

Limitations

Backplane boards or boards .250 in. thick with 8:1 aspect ratio or higher

Through hole via’s less then 0.010” in panels that create a 10:1 or greater aspect ratio begin to restrict wet chemistry flow. Plasma has the advantage in creating gas penetration in these small via’s by utilizing vacuum to move process gas

through the hole.

Plasma Advantages

Laser formation

Most blind via’s today are drilled using laser oblation. The laser

process typically leaves 3-10µ of resin on the capture pad

along with traces of carbon. Both must be removed for

successful electroless Cu deposition.

Blind via’s

Plasma Advantages

Plasma treating laser formed via’sPlasma desmears resin from laser formed via’s with a similar

process as through holes. The blind aspect of the hole does

not cause limitations. Plasma is not restricted by via diameter.

PermanganateTypically under 70µ, Wet processing causes 3 problems with Laser

BVH. 1. The via diameter (as with a through hole) will not allow good

flow.2. The remaining carbon is chemically resistant. 3. If the resin has reinforcement, wet processing causes wicking

and aggressive undercut.

Blind via’s

Plasma Advantages

Hybrids

Hybrid panels consist of several types of material. Mixing flex

with rigid epoxy or polyimide resins are the most common

types. However today PTFE is mixed with epoxy, LCP with

polyamides and non woven Aramids with modified blends of

epoxy. The materials in these type panels etch or activate

differently

Mixed-material PCBs

Plasma Advantages

PlasmaPlasma has the capability to mix gasses in the same process to

treat different materials. For example when PTFE and epoxy

are mixed two steps are used. First step for desmear and the

second for activation in the run

Permanganate

Wet processing Hybrid panels is not successful due the

chemistries inability to treat different materials. For example

PTFE and epoxy mixed panels would require 2 separate

chemistry lines. One to desmear and one to activate.

Mixed-material PCBs

Plasma Advantages

Plasma vs. Permanganate

Thank You