|
|
|
|
|
01/10/2007
 Email to a friend
 Comment on this article
|
Working with a major Tier One supplier has allowed a specialist supplier of room temperature vulcanising (RTV) silicones to share new knowledge on the effective sealing of electronic assemblies.
For TRW engineers, in their design and production of engine management modules that control injection and peripheral functions, key requirements are the prevention of vibration and the ingress of moisture into the system.
Initially these modules used die cast aluminium housings with soft cut gaskets to provide a seal and screws as the method of final assembly. While functional, there was potential for unwanted screws to rattle around and they represented both additional products and additional assembly operations.
The development of a plastic housing made from a PBT/polycarbonate alloy provided the opportunity to build the connector as an integral part of the housing and achieve cost savings by the removal of peripheral seal screws through the use of RTV sealant.
RTV silicone used in the assembly process removes the need for a pre-cut fixed gasket and a hermetic seal was produced around the perimeter flange of the housing. The need for screws was removed and assembly was eased through the use of heat stakes.
However, the move from batch to volume production resulted in a new set of requirements that needed to be resolved. One of these was the need to speed up the curing time of the lid sealant to reduce the time from final assembly to dispatch. A heat cure system was considered and trialled but was found to have the potential to damage the electronic components.
At this point, UK company Techsil, which has specialist knowledge of RTV silicones, began to work closely with TRW. The company was able to establish that inconsistencies in performance over time were down to a subtle variation of changes in the tooling used to make the plastic moulding, the use and poor cleaning of mould release agent from the component parts and a slight bowing of components through amended tolerances.
In a module that now included an addition-cure thermal transfer compound and a condensation cure gasket, there were initial concerns that using the two materials together may result in inhibition issues. Techsil was able to conduct extensive tests to confirm that the materials were compatible
Through the use of RTV silicone in the assembly process TRW has removed more than 20 screws from within the assembly, improved IP ratings from IP 44 to IP69, designed a module that withstands vibration factors of six times the original production unit, and improved the heat dissipation of the unit by a factor of two by using updated thermal compounds.
|
|
| |
Author
Roger Bishop
|
| |
| |
Copyright European Automotive Design.
See Terms and Conditions.
One-off usage is permitted but bulk copying is not.
For multiple copies contact the sales team.
|
| |
|
|
| |
To access the whitepaper section you need to complete our 60 second registration process. Once completed this then allows you to download any and all white papers, register for e-zines and access our detailed supplier directory for FREE.
If you are all ready a registered user then enter your e-mail address and login.
You will need to have logged in prior to entering your comments in the boxes provided.
|