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Evaluation of the adhesive
How can we check whether the adhesive hardens?
How can we optimize the hardening conditions for adhesive?
Check the hardening process by means of differential scanning calorimeter（DSC).
To obtain more precise duration of the hardening process, we analyze the quantity of residual element by means of FT-IR.
How to select the adhesive that has high reliability?
We evaluate the adhesive including its compatebility with the surface joining material.
| Accelerated aging test | Aging test under high pressure / high humidity environment (Pressure Cooker) Aging test under temperature / humidity stress environment (Isothermal humidistat) |
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| Destruction test | Check the destruction (defect) mode by means of SEM, etc. |
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Cohesion failure: Harden adhesive crumples up from its insideAdhesion becomes less due to the hardening failure of the adhesive or the hydrolytic cleavage in the molecule Interface: Peeling off from the joining surface.Most of the cases, the contamination on the joining surface is the cause. |
| Root cause analysis | |
| - Insufficient cohesion strength. (Measure hardening stage (rate) by means of FT-IR) - Contamination on the surface of the joining material (XPS) |
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Detect dimethylsiloxane on the surface of the joint material where the adhesive peels off (Foreign material on the surface caused the weak adhesion.)
Quality issue around the adhesive（Corrosion, ion migration)
In addition to hardening agent, the adhesive is generally used after denatured with diluent, filler, or additives. Resin generates halogen, water, or carbonic gas, and hardener generates amine, diluent or elasticizer generates organic substances, which all may cause the quality trouble.
Root cause: Ionic impurity
- Corrosion (Chlorine / Nitrate / Nitrite / Sulfate ion, etc)
- Ion migration (Chlorine / Bromic / Phosphate ion, etc)
[Example] Separatio in the wirebonding
Judging from the Cl detection in EPMA, we suspect the halogen element contained in the adhesive caused corrosion in the bonding area.
Root cause: Gas emission from the Organic compound (by heat)
- Contact defect (Silicone)
- HDD head crash