Bonding

Connecting Microfluidic Chips with and without Glue

In order to achieve closed fludic channels MEMS technologies offers different – material dependent – methods. The GeSiM engineering service covers:

  • Anodic bonding
  • Silicon fusion bonding
  • Die bonding using adhesives
  • Wire bonding

 

Anodic Bonding

This process generates very tightly connected layers, produced by the application of high voltage and high temperature, and is ideal for the irreversible covering of microfluidic channels.

  • Bonding of double and triple sandwiches of silicon and Pyrex glass
  • Maximal substrate diameter: 4 inches (10 cm)
  • Process temperature between 300°C and 450°C.
  • Bonding with or without prealignment. Aligning accuracy ≥ 5 microns.
  • Bonding of insulator (Silicon oxide SiO2 or Silicon nitride Si3N4) silicon surfaces.

 

Silicon Fusion Bonding

  • Adhesive bonding after wet chemical pretreatment of substrates in strong acids
  • For double sandwiches of (micro-machined) silicon
  • Maximal substrate diameter: 4 inches (10 cm)
  • Process temperature between 950°C and 1100°C under nitrogen atmosphere

 

Die Bonding Using Adhesives

  • Computer Aided Design and sieve production for screen printing of adhesives
  • CAD and preparation of polymer spacers
  • Adhesive die bonding on whole wafers or on single chips
  • Aligning accuracy ≥ 5 microns
  • Usage of conductive adhesives to interconnect electrodes of top and bottom substrate of the die bonded sandwich
Bonding-Examples-2

a) Silicon-glass sandwich, b) Glass-silicon-glass sandwich (Patent 01993578.2-1524), c) 35 µm thick polymer layer on top of a glass wafer with SiO2– insulated platinum electrodes, d) Glass-polymer-glass flow through cell, assembled by die bonding using photolithographically patterned polymer spacer and screen printed adhesive Patent PCT/DE 01/03324) (From left to right)

Wire Bonding

  • On or between glass, silicon, ceramic, printed circuit boards with metal bond pads.
  • Wire material AlSi1, diameter: 25 microns.
  • Minimal bond pad area 30 x 30 microns².
  • Sealing of bond wires with epoxy.