Decapping chips with rosin


Disclaimer: The operations described in this article are dangerous.
Proceed with caution.

  • Always wear safety glasses—splashes can damage your eyes.

  • Rosin fumes are harmful. Use proper ventilation and conduct the process outdoors.

  • Rosin should be heated to at least 300°C.
    Ensure you have a safe working area to prevent fires.

I assume no liability for any damages or injuries resulting from following this guide.

Effectiveness

Rosin is a useful tool for decapping chips but is not an universal solution.
Some epoxy materials do not dissolve in rosin at all.

Resistance scale

We can categorize package types based on their resistance to rosin, using a scale from 1 to 5:

  • 1: Fully dissolves in rosin, often within 20 minutes at 300°C.

  • 2: Slower dissolution due to some filler materials slowing the process.

  • 3: High filler content prevents full dissolution.
    Over time, the filler may detach from the die.

  • 4: Slightly affected, becoming more fragile but still difficult to remove.
    May leave stubborn residues, sometimes impossible to remove.

  • 5: Completely resistant to rosin, regardless of duration or temperature.

Polyimide removal

Polyimide can be attacked by rosin, though the process is slow at 300°C.

However, combining rosin with the torch/heasink method can effectively remove any polyimide residues.

Saturation

Over time, rosin becomes saturated with dissolved epoxy. This reduces its effectiveness and can lead to epoxy residues contaminating decapped dies.

To maintain effectiveness:

  1. Replace rosin when it becomes saturated.
  2. Avoid using old, contaminated rosin for fresh decapping operations.

Residues and contamination

Residues from dissolved epoxy accumulate at the bottom of the container, contaminating fresh rosin if not cleaned properly.

Solution:

Use two separate containers:

  1. Primary container: for dissolving chip packages.
    It will accumulate heavy residues, leading to dirtier dies.
  2. Secondary container: for cleaning minor residues from dies.

Cleaning the steel test tube/container is difficult. If residues persist, using a separate container for the final cleaning process is recommended.

Cleaning procedures

Cleaning dies

  • Use acetone to clean dies after removing them from rosin.
  • Caution: Placing hot materials into acetone can cause violent splashes.

Cleaning hands and clothes

  • If rosin gets on your hands or clothes, use cooking oil to remove it before washing with soap and water.

General procedure

Here I will describe my procedure to decap chips with rosin.

Most of the ideas comes from wer, a member of the siliconpro0n discord channel.

Equipment

You need some equipment to cut the top of the steel flask. I used a hacksaw.

Setup

  • The solder pot is filled with sand and will heat the steel tube.

  • The thermocouple is placed in the steel tube to monitor the temperature.

  • Rosin have to be heated up to at least 300°C.
    Heating more will result in more fumes, but should speed up the process.

Rosin should take about 20min to get to 300°C.



Steel wire is used in combination with the steel filter
to easily dive and retrieve the dies in rosin.



I use 2020 extrusions for the tube holder.


Note: you can add aluminum foil like this to keep/increase heat.
Just don’t place foil on the front or the buttons will melt…

Process

  1. Put a few dies in the filter.
    Be careful, multiple dies may stick together if placed in the same filter.
    You can use multiple filters to avoid this problem.

  2. Submerge the filter in rosin and place cotton on top to block fumes.

  3. Wait for about 30min and check the dies.
    If epoxy is not dissolved, shake gently and wait more.

  4. After some time or if epoxy is dissolved, rince the dies in acetone.
    Be careful and wait at least 3 seconds before pouring the filter in acetone, or the reaction will be a little explosive (wear safety glasses).

  5. If epoxy is still on the die, try gently to remove it with something soft enough to not scratch or damage the die. You may have to put the die in rosin again and repeat the procedure.

  6. Clean the die using acetone.

Be very careful with small dies:

  • A small die is way too easy to lose forever in thick rosin…
  • Residues are harder to remove and dies are harder to clean.

I recommend using rosin with relatively big dies to start.

Decapping small dies with rosin requires some experience.

If you really have to decap small dies

  • You can plug a second filter so any small die in the first filter will be stuck here.

  • You can stack multiple filters if needed

Cleaning dies

Polyimide

  • If the die have polyimide on the surface, you can just rub it with a q-tip and acetone to remove soft epoxy residues and/or rosin residues.

  • When the surface is free of epoxy/rosin residues, you can use the torch/heatsink method to burn the polyimide. Then use rosin again to remove any residues on the surface of the die.

Dissolve rosin

  • Rosin is relatively easy to clean/dissolve in acetone or alcohol. wer is using an ultrasonic cleaner for that.

Modern chips

  • If the chip is modern enough and planarized, chances are the surface is not fragile and you can clean it gently with a q-tip and acetone.

Older processes

  • Older chips tend to have a very thin passivation layer and are easy to scratch/damage. Prefer gentle methods like a warm acetone bath in an ultrasonic cleaner.

  • Be very careful and don’t put acetone directly in the ultrasonic cleaner, vapours may cause fire/explosion. Always use some small PE (or any acetone resistant) plastic container.

  • Older chips are also much easier to damage with heat, so be very careful if you try to use the torch/heatsink method.

Some results

Mediatek MT8292N
  ☐ Rosin for 20 min. Epoxy is soft.
  ☑ Removing soft epoxy with a q-tip and acetone.
  ☑ Rosin for 40 min to clean epoxy residues.
TI-82 Plus CPU
  ☑ Rosin decap in 30 min
  ☑ Stripped the polyimide layer
Analog Devices AD6480JST
  ☑ Rosin decap in 40 min
  ☑ Stripped the polyimide layer
Hitachi HD63C09 CMOS MPU
  ☐ Rosin decap in 50 min. A lot of residues.
  ☑ Removing residues for 40 min in rosin.
  ☑ Stripped the polyimide layer
  ☑ High resolution panorama
National semiconductor AD6266 MM9248-VS
  ☑ Rosin decap in 40 min.
  ☑ Stripped the polyimide layer

Observation

Most of the failures with hot air are because of polyimide sticking to epoxy.

If you can’t strip polyimide, rosin will only do half of the job.

Failed attempts

  • About 1/3 of the chips I tried to decap were not attacked by rosin.
    Example: Epson SRM2264LM

  • Rarely, rosin attacked most of the epoxy but some residues are just impossible to dissolve.
    Example: Mitsubishi M5L8085

Latest update: 2025 feb 9.