1. Pressure Sensitive Adhesive (PSA)
The most popular attachment method is the Pressure Sensitive Adhesive (PSA). Standard PSA are non conductive and are dimensioned to not cover the entire gasket surface to ensure direct electrical contact. The constraints applied on the adhesive vary in large proportions depending on the type of application. There are limited constraints for static applications because the adhesive is just there to hold the gasket the time before it will be compressed. At the contrary, for dynamic applications, constraints increase and especially when forces are exerted in the horizontal axis (for ex. during blade or module insertion) which tends to push the gasket. Schlegel Electronic Materials, Inc. has selected 3M acrylic based adhesives with high shear strength values* to guarantee adhesions even in the most challenging dynamic applications.
* To ensure the maximum bond strength from the adhesive, please follow the taping procedure.
| T Tape | R Tape | H Tape | |
|---|---|---|---|
| Adhesive | Acrylic | Acrylic | Acrylic |
| Liner | Extensible polycoated kraft | Polycoated kraft | Extensible polycoated kraft |
| Adhesive thickness | 5 mils (0.1270 mm) | 6 mils (0.1524 mm) | 5 mils (0.1270 mm) |
| Substrate | No carrier | Polyester carrier | No carrier |
| Application | Pressure | Pressure | Pressure |
| LT operating temp. | 180øF(82.3øC) | 200øF(93.4øC) | 250øF(121øC) |
| ST operating temp. | 250øF(121øC) | 300øF(149øC) | 350øF(177øC) |
| Elongation | 8% | 3% | 8% |
| T Tape | R Tape | H Tape | |
|---|---|---|---|
| Shear/Stainless steel | Immediate | 24hrs | 72hrs |
| PSI | 14.7 | 34.8 | 47.0 |
Detailed 3M technical datasheet available on www.3M.com
Conductive adhesive can also be proposed and are recommended in specific instances (eg. very small profiles ).
A) Taping procedure
Clean the metal surface with typical surface cleaner solvent. For example, use isopropyl alcohol or a heptane.
Wait until the bond surface is clean and dry because grease, oil or mold release chemicals could create a barrier between the adhesive and the substrate and hence affect the bond strength.
Wearing finger cots is suggested as a finger print is one of the contamination sources.
Remove release liner slowly and carefully. Do not allow the release liner to tear during removal. Confirm that no release liner remains on the adhesive.
If the release liner tears and the remaining release liner cannot be easily removed, discard gasket and use a new gasket.
Bond strength is dependent upon the amount of adhesive-to-surface contact developed.
Dust, fiber or particle contamination will affect the tackiness of the adhesive and reduce the contact surface area.
Apply finger or hand pressure along the full length of gasket to completely bond to the metal surface. Confirm that pressure has been applied to both ends of the gasket to bond the adhesive to metal surface.
Firm application pressure can develop a better adhesive contact and improve bond strength.The gasket and the tape can be used ONCE only.
The gasket should not be peeled off and re-used again because the tape will lose its bond strength and will have adhesive issues.
The ideal tape application temperature range is 21°C to 38°C. Initial tape application to surfaces at temperatures below 10°C is not recommended as the adhesive will become too firm to adhere readily.
The bonding strength increases as a function of time. Time allows the adhesive flow on the substrate. In theory 72 hours dwell time is requested however about 2/3rd. of total adhesion strength is reached after 24 hours.
B) Adhesive removal
3M has developed a Citrus based Cleaner especially to ease the removal of adhesive residues .
Further information can be found at www.3M.com
2. Rivets
Some profiles can be mounted using rivets. Plastic inserts are therefore positioned to reinforce the holes and ensure a good
3. Clips
Several profiles with plastic clips are currently available .The conductive fabric is therefore positioned in the clip area to ensure electrical path.
4. Self mounting
5. Kiss cut
