Hybrid panel heated plate study

Currently the curing of the ASIC glue for the hybrid panels are done at room temperature.This is a study to determine if the panel can be heated to reduce the current cure time of 24 hours per ASIC placement session to speed up production.

Extract from TRA-DUCT 2902 datasheet:

So yes, the glue can be heat cured...

However the panel cannot be placed in an oven because of the vacuum hoses, so an alternative needs to be found. A proposed alternative is to use a heating plate that can be placed under the current curing setup. Flat heating elements are available.

Hybrid panel heated plate study

First test is to determine curing rates, this is done with test samples of glueon glass slides in an oven.

Several tests are done at 30oC, 40oCand 50oC. Samples are prodded everyhalf an hour.

All temperatures give the same result,a hard shell forms on the glue after 2 hours.

The hard shell is self supporting but not completelycured, it can be dented with a sharp point indicatingthat the glue interior is not completely cured. But could this be good enough to support the ASICswithout the ASIC vacuum jig once it has reachedthis state? Next stage is to design a system that can be usable.

Hybrid panel heated plate study

After some searching we found two companies who sell flat heating plates, Minco (Based in France) and Watlow (Based in Nottingham):

Minco:HK5529R101L12BUnit price : 185.00€Minimum Order Quantity : 25 piecesLead time : 7 to 9 weeks from order receipt.

4,625 Euros to buy a heater! Awful customer service, two months to get a quote.

Watlow:Helpful on the phone, willing to sell a single item. £63.20, bargain!

Hybrid panel heated plate study

Proposed hybrid panel heating system is as follows:

Hybrid panelPanel vacuum jig

Metal block

Heating element Insulating sheet of glass (Temporary, will get something better later)

The heating element is stuck (Pressure sensitive adhesive) to the metal block, then this just needs placing under the existing setup.Panel vacuum jig is placed on the metal block without any fixings or screws.No modifications are needed to the existing mechanics.

Hybrid panel heated plate study

Heating element is self adhesive, quick to fit on the heating block.A “K” type thermocouple is embedded into the heater.

Lets try it out...

Hybrid panel heated plate study

Based on oven tests a target temperature above 30oC is needed.Thermocouple on the heater and another one on the panel surface (On an ASIC pad)is connected to a temperature measurement unit.A dual power supply is connected and turned up to the maximum of 70 volts (370mA drawn)After over 2 hours the temperature settles at 34.4oC, not as fast as hoped but it got there. Time to glue one glass ASIC hybrid.

Bare stencil used to put an additional glue sample directly on a hybrid as a “Prod and stir” sample

Hybrid panel heated plate study

A glass ASIC hybrid is placed. A “Stir and prod” sample is placed which is then checked periodically. Sample forms a hard shell after two hours as seen on previous tests. Assembly is left for a few more hours, ASIC jig is removed, heater turned off and left to cure overnight.

Hybrid panel heated plate study

Results look good, dots are well defined, glass ASICs have not moved position. The glue is completely cured on the sample.

Hybrid panel heated plate study

Ok, some real tests now. First test, temperature stability, how much control is needed.A proper temperature monitoring system is now used, a HP Data logger connected to a PCto capture the data. One day short test and one three day long test.

(Windows 95 PC!)

Hybrid panel heated plate study

3 day test. Temperature is very stable to within a degree, lucky.The procedure should work without requiring a controller.

Hybrid panel heated plate study

Second test. 2 Hybrid glass ASIC cure test. How stable is the temperature while the panel is being worked on. How smooth is the procedure to change over the ASIC jig.

Hybrid “Stir and prod”sample

Room temperaturecomparison sample

Procedure works well.Hybrid glue sample cures as predicted.glass slide sample still stirrable long after procedure is finished.

Hybrid panel heated plate study

There is no significant change in thetemperature during the procedure. Swopping the ASIC jig over takes 5 minutes.finished hybrids look good, includingthe positions of the ASICs.

Hybrid panel heated plate study

Third test. Produce samples for full testing. Real ASICs. Three heated hybrid cures done in a single session. Three room temperature hybrid curesfor comparison (Done later). A timer is added to start the heater early in the morning so the setup is ready to work on at 10am. Timer is from RS components, stock number 329-676 £10.69.Timer is only to turn heater on, heater is turned off manually.

Hybrid panel heated plate study

Procedure goes smoothly.

Hybrid panel heated plate study

Disaster!Something is wrong with this panel.Height distance between jig pads and ASIC pads too big.

This ASIC fell off.

This ASIC cameoff easily.

This ASIC wasfairly firm.

Hybrid panel heated plate study

Conclusions (So far):

•Procedure requires some organisation and timing.However there is a two hour gap between placements and the final jig placement can be leftovernight with the heater on.

•Total expenditure is a £63 heater and a £10 timer. The metal plate and base are easy to make. The power supply type is already being used on the project.

•The heating system can be added to the current setup without any additional modifications.

•Positioning (Using visual inspection) of ASICs is the same as room temperature cured ASICs.

•CMM results need checking because of problems with last panel.

Next steps:•Shear testing in Berlin (We are already talking to this group).•A complete 8 hybrid gluing session (We have run out of panels and ASICs).•Other groups trying out the procedure.