I am in Greenwich, London at the moment at the ESTC2008 (Electronics and System-Integration Technology conference). And I am going to enjoy three day of electrical engineering geekery at it’s finest.
I am starting now with a session on “Electronics Integration for Healthcare: Materials and Processes”by James Lee.
The first talk is on “Versatile low cost wafer-level packaging enabled by powderblasting“.

Powderblasting is basically the same then sandblasting just on a smaller scale. Instate of sand you use alumna (Al2O3) powder with a diameter of about 5 to 50 µm. He is applying this to Wafer level packaging. The presented work is on a vargus nerve interface. And the Powderblasting is used for via forming and cavity forming in an silicon wafer.

Transverse and Through silicon vias are possible. For the Bonding itself he recommends Anodic bonding. And the cool thing is that you actually don’t need a cleanroom for the processes.

The mask is a PVA Dryfilm resist. 25µm particles are used. Minimum hole diameter is 140µm (for 140µm thick) in Si. Pitch is determent outer Diameter +40µm. Roughness is about 2µm. They also doing double sided blasting.

Now Natalia Beshchansa is talking about an “Investigation of thick film electronic packaging materials in dynamic contact with artificial body fluids”

It is mainly focusing on implants and the biocompatibility of this thickfilm materials, mostly for packaging and connectivity applications. She is explaining the the potential failure modes. Materials are for example Ag-Pt or Ag-Pd.

The experiment was basically to introduce a flow of artificial body fluids (blood for example) over the samples to analysis the degradation. Very interesting, she is showing the defects of the surface topology appearing over time. And it seems that the fluid building up a layer that first increases the surfaces roughness. Now she is explaining that the materials absorbs quite a lot of Cl and some P and Mg in the Ag-Pt structure. And the films are also oxidised.

Property evaluations of polymers used as housing material for passivation of electronic devices by Eberhard Engeling. After telling us why you have to encapsulate electronics and that he is using Parylene C, Dynamask 5000, Multi-Cure. He is explaining that you don’t get hard data on material properties necessary for medical applications.

One of the properties he is testing for is diffusion properties (permeability). He is actually treating the polymer as a semi permeable membrane between to chambers and and then measuring the ions travelling form one side to the other. He can also provide to provide data o the cell cultivation rate on the polymers.

Kristin Imenes In now talking about “Micro Ribbon Cable bonding for Implantable devices“.

Basically How to wire your pacemaker. The cable so far have been quiet big and chunky. To reduce the size she is suggesting a ribbon cable with 13 Cu Conductors, diameter 45µm ad 71µm pitch(temp-flex) insulation made from PFA (teflon like). Wire stripping is done by laser of plasma etching. Good result were shown by the use of IR/fs laser. Bonding has been don by wire bonding to the gold coated glass substrate of the glued cable (wedge bonding). The flip chip like bonding with non conductive adhesive is beneficial because of the remaining pitch due to the just partially removed insulation.

It is pointed out that plasma etching is has the advantage over Laser ablation , that the wires are not damaged. Wedge bonding (Copper) is working. The non conductive gluing as well, but is showing some critical alignment challenges.

All together this was a very interesting session. Now lunch is on the program.