JetEtch Automated Acid System
Many types of modern packages require the use of mixed etchants. For optimal package opening a single mixed acid ratio is not sufficient—you must have a choice.
Modern packages, particularly those constructed with copper lead frames or other copper components, require exact mix ratios for precise and reproducible package opening, not only to preserve structural components, but also to maintain electrical functionality.
Optimization is not possible if your system is only capable of using a single etchant mix. Glob top packages (chip on board, chip on flex), die down BGAs and stitch bond (secondary bond) exposure are just a few examples of applications needing mixed etchants.
In addition to nitric acid and sulfuric acid operation the JetEtch automated acid system offers the widest range of on demand mix ratios in the industry. The user simply inputs the mix ratio desired. The correct volumes of each acid are then automatically passed to a Teflon pre-mix chamber and from there the mix passes to the etch head assembly.
Programmable Acid Mix Ratios
Fuming
Nitric Acid |
Fuming
Sulfuric Acid |
 |
|
Fuming
Nitric Acid |
Fuming
Sulfuric Acid |
| 6 parts (86%) |
1 part (14%) |
1 part (14%) |
6 parts (86%) |
| 5 parts (83%) |
1 part (17%) |
1 part (17%) |
5 parts (83%) |
| 4 parts (80%) |
1 part (20%) |
1 part (20%) |
4 parts (80%) |
| 3 parts (75%) |
1 part (25%) |
1 part (25%) |
3 parts (75%) |
| 2 parts (66%) |
1 part (33%) |
1 part (33%) |
2 parts (66%) |
| 1 part (50%) |
1 part (50%) |
1 part (50%) |
1 part (50%) |
| 1 part (100%) |
0 parts (0%) |
0 parts (0%) |
1 part (100%) |
| Temperature selection is key. |
SULFURIC ACID
At temperatures above 150°C when oleum vapor is present, plastic encapsulant is rapidly removed, with minimal metal etching. At lower temperatures however, with less oleum vapor present, longer etch times are needed, leading to the possibility of excessive metal loss.
NITRIC ACID
Fuming nitric acid is a complex solution containing a number of reactive ion sand compounds, dinitrogen trioxide (N203) and the N03 anion being the most prevalent. At temperatures below 75°C there is little metal corrosion, whereas at higher temperatures, the etch rate increases, as does the potential forexcessive metal etching.
One or two degrees change in etch temperature can make a difference between a controlled etch process or a disruption of critical structures such as die coats.
The JetEtch has excellent temperature control, achieving a stable temperature within ±1 percent of the programmed temperature, irrespective of the dimensions of the package being opened or of the acid volume selected.
Acids used for decapsulation are commercially available in varying concentrations. We recommend using 90 percent fuming nitric acid, 20 percent fuming sulfuric acid and 96–98 percent sulfuric acid; although other concentrations may be used.
Safe, Simple, Secure
The JetEtch automated system does not require a change of acid waste bottles before changing etchants.
The automated acid system is equipped with two waste bottles. Upon selection of a pure acid, or of a mixed etchant, the SmartWare diverter valve automatically feeds waste acids to the correct bottle. Waste bottle selection is automatic. The selection is based on either the pure acid selected, or the acid mix ratio programmed into the unit. Unlike less sophisticated systems you never have to change a waste bottle when you need to change acids.
To minimize handling of dangerous chemicals all members of the JetEtch series of decapsulators use standard acid bottles for waste acid containment.
For high acid use installations the JetEtch series can be supplied with a large bottle option and also a waste acid dilution option that connects directly to an acid drain.
The bottle caps are designed to prevent dripping and splashing of acids. Bottle changing has never been so simple, or so safe. The photos show that the bottle caps are now an integral part of the secondary containment unit. To change a bottle simply unscrew the cap and tilt it out of the way. As the acid delivery siphon tube is not connected to the cap there is no chance of acid splashing or dripping. Simply place the siphon tube into a fresh bottle of acid, replace the bottle into the containment unit, flip down the cap and tighten.
For ultimate safety the volume of the secondary containment unit is 110% of the bottle capacity, in compliance with SEMI S-2 specifications.
SmartWare
The JetEtch automated acid system incorporates a range of acid mixing options. Once an acid mix is selected Nisene Technology Group’s SmartWare Diverter Valve automatically selects the appropriate reservoir bottle to accept waste acid.
The JetEtch system offers six etchant mix ratios, easily selectable from the keypad. Once an acid mix ratio is selected the SmartWare diverter valve automatically selects the appropriate reservoir bottle to accept used waste acid after decapsulation.
