How to decap an IC

[Grant Stockly]

This is a collection of instructions from the web on decapping ICs. I have not successfully decapped any ICs yet, but when/if I do I will post my results.

[Grant Stockly]

From: Jon Hiller : hiller-at-anl.gov
Date: Thu, 24 Jan 2002 19:26:21 -0600
Subject: IC package removal

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Body of Message


Does anybody have a chemical solution for removing IC packaging without
damaging the internal components? Simple grinding from the top down is not
suitable because I need all the interconnects intact. Any help in this
matter is greatly appreciated.

Sincere regards,

Jon Hiller
================================================== ================
Jon M. Hiller
Argonne National Laboratory
Materials Science Division
Electron Microscopy Center
Tel: 630-252-9558
Fax: 630-252-4798
Email: hiller-at-anl.gov
================================================== ================


From daemon Thu Jan 24 19:34:57 2002

[Grant Stockly]

From: Diane.Ciaburri-at-gd-ais.com
Date: Fri, 25 Jan 2002 08:50:58 -0500
Subject: Re: IC package removal (LONG)

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Jon,

I assume you're speaking about plastic packages since you want a chemical removal technique. Below your message is a summary of responses that I received when I asked a similar question. I can't comment on them, because my project dried up after I asked the question and I never got to try any of the techniques, but there look like some good ones.

Diane Ciaburri
General Dynamics
Pittsfield, MA


<Note from logjam, the following posts until noted by me are a part of this e-mail. I'm separating them for readability. I'm also fixing the line break issues that make the post very hard to read and doing some minor formatting>

[Grant Stockly]

<Part of the last post>

Here's the summary (long) for all those interested in deencapsulating plastic encapsulated ICs. I have no preferences as I haven't tried any yet, but thought the fuming sulfuric acid might be 'fun'. Thanks again!

[Grant Stockly]

<Part of the previous post>

-- [ From: Garber, Charles A. * EMC.Ver #3.1 ] --
Hi Diane,

The way this is generally done is to mill the plastic down on a grinding wheel to the point where only a fairly thin layer of plastic remains.

Then, using a plasma etcher, and a mixture of oxygen to CF4 (for example, 30% oxygen/70% CF4), whereby the oxygen etches away the plastic and the CF4 etches away the glass frit that is usually found in the plastic, you can remove the remaining plastic (package) without damaging the device itself. Different people like to use different gas ratios, of course, and that is probably a function, at least to some degree, of the concentration of glass frit in their particular plastic.


The SPI Plasma Prep II unit, as shown on URL http://www.2spi.com/catalog/instruments/etchers1.html in the world, is probably the most widely used unit for doing this type of operation. It is inexpensive and highly reliable, and requires virtually no maintenance.

Chuck

[Grant Stockly]

<Part of the previous post>

The ion beam approach works well. I have not used it recently on finer pitch ICs. With as-built feature sizes of 2-4u, it is fine. It will stop at the passivation and leave the Al bond wires intact. The resulting package looks like it has a V-shaped pit in it (which it does). The extent of the pit depends on the size of the die and if you want to blast down to the lead frame or substrate.

I have not done this on finer pitch devices. I would be a bit skeptical about these mostly because of the smaller bond pads. The etching would still stop at the passivation.

There are numerous places in Silicon Valley that do this on an outsource basis. Typical costs are about $75 per IC. I can get some contacts for you if you'd like.

gary g.

[Grant Stockly]

<Part of the previous post>

Diane: attached is a text document outlining the procedure my FA lab uses. Yellow fuming nitric is usually the acid of choice. If you can get a few extra parts to practice on, that would be best. And you're right, plasma takes FOREVER. If I can be of any more help, please let me know.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Becky Holdford (r-holdford-at-ti.com)
972-598-1291 (pager)
KFAB Physical Analysis Labs--SEM/FIB/FA
Kilby Center West
Texas Instruments, Inc.
Dallas, TX
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

TOOLS, EQUIPMENT, & SUPPLIES

1. Milling machine and appropriate end mills
2. Stabilo SuperFine OH pen or equivalent
3. Fume hood properly equipped for exhausting acid fumes and solvent vapors (see reference 3.4)
4. Explosion proof hot plate (see reference 3.4)
5. Ultrasonic cleaning apparatus
6. An optical microscope capable of 100X to 500X magnification, equipped with a lighting system.
7. Chemical resistant latex gloves
8. Chemical resistant laboratory coat
9. Chemical resistant safety glasses (see reference 3.5)
10. Hand tools (tweezers, scalpels and etc.)
11. Plastic micro-pipette
12. Fuming red nitric acid
13. Yellow nitric acid
14. Methyl alcohol
15. Acetone

1. RECORDING OF PACKAGE MARKINGS
Record all of the device markings that are on the top and bottom sides of the devices prior to starting any of the decap operations.



2. CAVITY MILLING
Determine the exact location of the chip within the package and mark the top of the device package showing the chip perimeter, using a Stabilo SuperFine OH pen and a straight edge. A SAM plot or X-ray image may be used to help determine the exact location of the chip and also to determine the thickness of the mold compound covering the chip.


Note: This should be done on devices having large chips. Devices with small chips (less than 0.125 inches in their longest dimension) do not require this step.

Mill a cavity out of the plastic package that is centered over the chip. The size of the milled cavity should typically be .050 to .100 inches larger than the length and width dimensions of the chip. The depth of the milled cavity depends on the thickness of the mold compound and the location and loop height of the bond wires. During the milling operation use a vacuum line to pick up the loose plastic particles generated.

Caution: do not mill into the bond wires or the chip. Mill counter bores on devices with chip dimensions greater than 0.400 inches on a side. These counter bores should be made on one or more levels within the bond pad perimeter and at the outermost corners of the cavity (this is necessary to facilitate etching of the mold compound at the corners of the chip before the sides are exposed and subsequent damage to the leadframe). Care must be taken during the milling operation to avoid excessive pressure on the mill resulting in filler induced damage to the chip P.O. The end mill should not bind, bend, or "smoke" during the milling operation.



3. PACKAGE ETCHING
All etching must be performed in a chemical hood that meets the requirements defined in references #.3 and 4. Heating of acid or device prior to application of acid must be done using an explosion proof hot plate that meets the requirements of reference #4. Obtain the appropriate acid for use on the mold compound being removed. Following are the acids that have been identified for the removal of the various mold compounds. Mold Compound Acid/Temperature Shinetsu Red fuming nitric acid at 140-150 degrees Celsius Plascon & Sumitomo Red fuming or yellow nitric acid 140-150 degrees Celsius


Note: Fuming sulfuric acid reacts with exposed aluminum bond pad metallization and may result in ball bond discontinuity thus hampering further analysis.

• When using red fuming nitric acid it may be helpful to start the etching process using a mixture of red and yellow nitric acids in order to slow down the etch process until a "residue crust" is formed over the cavity and then switch to the red nitric acid.

• Apply the acid in drops using a plastic micro-pipette. The drops should be placed in the center and at the corners of the cavity in approximately a 1:1 ratio.

• Allow the acid to react with the mold compound and form a crust of dissolved compound. Caution: Do not allow the crust to dry out completely before adding additional drops of acid.

• Remove the dissolved material using cotton swabs or by rinsing with acetone when the dissolved materials threaten to spill over the cavity. Caution: Rinse the device immediately with acetone if acid spills onto the package pins.

• Soak the device in acetone for a minimum of 10 minutes, followed by a spray of methanol to remove loose residue and to clean the residue from the cavity rim.

• Perform a thorough microscopic inspection to determine whether all necessary areas of the chip are exposed.

• If dried mold compound residue persists on the chip surface, use the following in the order shown to attempt removal:

• Solvent bath (such as methyl alcohol) in ultrasonic cleaner

• Several drops of room temperature fuming sulfuric acid applied to the chip (with the chip at room temperature) for several seconds then rinse the device in DI water.

• Several drops of fuming sulfuric acid applied to the chip with the chip on a 100 degree Celsius hot plate. Note: Fuming sulfuric acid will attack aluminum bond pads and is therefore the method of last resort.

[Grant Stockly]

<Part of the previous post>

Can't comment on sulfuric, but I have used red fuming nitric at near boiling temperature. Apply acid, let react. Flush witn more acid, let react, etc.
Woody White

[Grant Stockly]

<Part of the previous post>
Diane,

Yes, hot fuming sulfuric and/or hot fuming nitric are used as standard procedures for removing plastic from IC's. The process is not quite that simple. For example, water rinses will almost certainly etch the bond pads on the IC and thus removing connection to the outside world. Additionally, the plastic contains fire retardants which some regions don't like being washed down the drain. There is more detailed help through EDFAS.org (one of ASM's branches). B&G International sells a very safe, effective etcher which performs decapsulation automatically in minutes.

I have no association with B&G International.

David Saxon
Analytical Microscope Services
11826 Reservoir Rd. E.
Puyallup, WA 98374
253-848-7701 voice & fax
email: info-at-analyticalmicroscope.com
website: www.analyticalmicroscope.com

[Grant Stockly]

<Part of the previous post>

Diane,

I used to do failure analysis on semi conductor memories which were starting to be made of plastic/epoxy with glass rods about 20 years ago.

I have some technics and possible help but its too much to write. Basically you drill a small hole about 0.1" deep then heat the IC on a hot plate and then you drop your acid to remove the plastic. I dont know chemistry, I'm and Electronics Technician. I did this work with a meterial sicentist, my mentor.

We used fumming sulfuric acid and fuimg nitric acid, also some type of organic pink and blue solutions to stop some of the acids etching effect.

The company back then was Burroughs Corp. today is Unysis.

I presently work for the U S Department of Energy in New York City. My phone number is 212 6203650, I'll be happy to walk through some ideas and things I learned.

Regards
Peter Roiz