How to identify and fix resin bleed in Die attach applications
Resin Bleed is the migration of liquid components from the adhesive onto the surrounding surface due to surface energy differences between the resin and substrate.
It can be caused by surface conditions such as the roughness or the cleanliness of the substrate. It can also be a result of unoptimised process parameters such as a wrong cure profile or too long dwell time.
Bleed onto the bond surface may cause poor wire bondability. It may also improve or lessen the adhesion of encapsulants and molding compounds.
Bleed or outgassing?
The first thing to check is to see if the issue is resin bleed or outgassing. Understanding exactly what you are looking at will help make sure that it is being addressed properly. Ask yourself these questions:
- Is the discoloration one sided or symmetrical without a clear boundary between the leadframe and the bleed?
Then it is likely outgassing. You could increase the airflow to try and resolve this.
- Does the pattern run along the etches/ridges of the substrate?
Then it is most likely bleed. In this case there should be clear separation between the discolouration and the leadframe. Try modifying the cure profile, clean the surface area or experiment with other materials.
Troubleshooting
We can generally attribute resin bleed to 3 main factors. Equipment, Processes and Materials. Following up we are listing the most common causes and the corrective actions that you could take to reduce resin bleed.
Equipment
| Possible Causes | Corrective action |
|---|---|
| Surfaces may be too warm | Ensure that the die attach is not warmed-up until ready for cure Make sure surfaces are not overheated |
Process
Causes:
- Surface may be too rough
- Surface may be dirty or unclean
- Dwell time before cure is too long
- Cure profile is too slow
Actions:
- Modify surface if possible to reduce roughness
- Clean surface prior to application of die attach
- Plasma cleaning often helps reduce bleed
- Increasing cure speed can help reduce bleed
- Increasing cure temperature can help reduce bleed
Materials
| Possible Causes | Corrective action |
|---|---|
| Die-attach may be particularly sensitive to bleed on a specific substrate | Discuss with your CAPLINQ representative to make sure you have made the correct product selection for your process |
Overall resin bleed and separation should not be an issue if the correct materials have been chosen and the process is optimised. There are multiple materials that have been developed to almost eliminate the chance of bleeding such as LOCTITE ABLESTIK QMI536NB and LOCTITE ABLESTIK 84-1LMISNB. Keep in mind that bleeding is not observed only in die attach but it can be found in any material that uses a base resin.
Caplinq offers a Huge range of Henkel Electronics Die Attach materials, Encapsulants, Underfills and Electronics assembly adhesives. We can help you choose the ideal non-bleeding material for your application. Contact us for more information.
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