Ceramic Lid Attach
APPLICATION NOTE: LOW TEMPERATURE GLASS SEAL LID ATTACHMENT PROCEDURE
This application note describes a process for sealing of lids to packages where the lids have been pre-coated and glazed with StratEdge low temperature glass (P/N 400289).
Equipment required: Spring clamps, glass covers, and a belt furnace.
The lids are 96% alumina ceramic with an attached glass preform. The recommended method of attachment is by glass reflow. The temperature profile should provide a peak of 330°C to 340°C. The parts should remain at the seal temperature (peak) for about 4 minutes. The furnace atmosphere can be air, but dry nitrogen is recommended to provide better protection for the device being packaged. A process should be developed and optimized with the specific equipment at your facility. Results will vary according to:
- The type of furnace employed: a) amount of heated length, b) belt speed, c) stability of atmospheric flows, and d) other physical characteristics such as belt width.
- The size and mass of the assembled part and fixture (used to keep the lid aligned) in combination. More overall mass requires more heat.
- The clamping force or amount of weight used. The weight must be sufficient to insure proper bonding, but not so great as to force the glass out of the joint. This can be accomplished with weights, spring clips, or other types of clamps. Two-pound spring clips (per package) have been found to provide satisfactory results.
Cleaning of the lids is usually not required. If cleaning is desired, immerse in acetone (ultrasonic cleaning is preferred), followed by two isopropyl alcohol rinses, and air dry or oven dry at 150°C or less.
Bake packages and lids as required for packaging application. Baking of the lids above 150°C is not recommended. Place the lid on the package and cover the top and the bottom of the package with a glass or ceramic plate. Sealing without the cover plate is NOT recommended. The ceramic lid is thin, and it may crack from sealing clamp pressure. The cover plate not only prevents cosmetic marring of the lid and package, but also distributes the clamping force evenly over the lid and package bottom.
The cover plates should be approximately 100% to 200% the size of the lid, and a minimum of 0.040" thick. Other materials may be used, but glass plates allow for convenient and accurate alignment of the lid.
With the lid and package sandwiched between 2 cover plates, secure the lid in place with a 2-pound clip. A 2-pound clip will work well for packages and lids approximately 0.2" in size in the 330 to 340°C profile described below. Larger packages or reduced sealing temperatures may require 4 pounds or higher clamping force.
Typical Furnace Profile
- Total time in the furnace is approximately 26 minutes
- Steepest heating ramp rate is approximately +100 °C/minute
- Steepest cooling ramp rate is approximately -50 °C/minute
- The sealing temperature is approximately 335°C for 4 minutes
Ceramic Lid Attach
APPLICATION NOTE: B-stage Epoxy Seal Ceramic Lid Attachment
StratEdge lids are provided with an attached epoxy preform. Store lids in a clean, dry environment. Lids have a shelf life of 6 months if stored at room temperature and a shelf life of 12 months if stored at +5°C or lower (refrigerated). Cap lids are installed as follows:
- Preheat oven to 155-160°C.
- Allow cap lids to warm to room temperature before proceeding.
- Handle using tweezers or finger cots in a clean area to avoid contamination.
- Position cover on the package and secure with a spring clip. Based upon the external perimeter of lids with .020" walls, for perimeter up to 1.4", use 1 lb. spring clip, and for perimeter up to 2.8", use 2 lb. spring clip.
- Cure clamped parts for 1 hr.
- Remove the assembly from the oven and remove the clips.
For further assistance, contact Applications Engineering at (858) 569-5000, or by e-mail at info@StratEdge.com.