Product category:
PCB Assembly Equipment and Tools
News Release from: Kern-Liebers USA | Subject: Metering pumps
Edited by the Electronicstalk Editorial
Team on 03 September 2002
Encapsulating electronic components with
polymer
The encapsulation of ignition distributors requires special materials and a dispensing system with precision temperature controls and exact material metering.
The encapsulation of ignition distributors requires special materials and a dispensing system with precision temperature controls and exact material metering Manufacturers of sensitive electronic components often use an encapsulating compound to guard against dust, moisture and vibration
This article was originally published on Electronicstalk on 5 Mar 2004 at 8.00am (UK)
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This under-hood application involves the protection of an ignition module against environmental factors and the high voltage output of the ignition system.
As vehicles become dependant on computer chips and electronics, it become important to protect these components against the constant heat, moisture, oil, dirt, vibration and - in this case - high voltage.
The requirements are very demanding: the encapsulating compound that fills the distributor modules must act as a high quality insulator protecting the electronics from continuous high voltage.
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The material must not contain any air inclusions (bubbles).
Bubbles lead to sparking which destroys the printed circuit board in the distributor.
This encapsulating compound consists of two parts; one is filled with a glass fibre.
Kern-Liebers Dispensing Technology developed a solution for this very difficult application in co-operation with the automotive component supplier.
During system development, attention is focused on temperature monitoring since acceptable results can only be obtained when specified temperatures are stringently maintained.
System temperature is continuously monitored at twenty measuring points and corrected if necessary.
Both material reservoirs are temperature-controlled, one at 80C, the other at 60C, preventing the formation of bubbles and allowing the material reach the required fluidity.
A vacuum system used in the reservoirs reduces the pressure to 3mbar, removing trapped air bubbles.
The parts are preheated to 60C, ensuring the mixed material retains it fluidity during dispensing.
The material is fed to the mixing unit by a reliable and proven media transfer system.
This system and all transfer hoses are temperature-controlled, keeping the material flowing properly.
A material ratio of 1:1 is precisely mixed with Kern-Liebers metering pumps ensuring an accurately mixed final compound.
Curing takes place in two, 5m continuous furnaces, the first at 80C and the second at 120C.
Overly high temperatures are also not permitted as the module electronics are temperature sensitive and can be ruined by excessive temperatures.
The system controller has the temperature indicators along with pressure sensors for the material reservoirs.
The operator keeps all system data in sight displayed on a monitor at the loading and unloading position.
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