Patent GB-940971-A (GB)
Title: Sealing quartz to metal
IPC: C03C27/04
Filed: 1959-11-05
Abstract: A quartz to metal seal structure comprises a quartz member, a thin coating bonded to the quartz, and having an outer metal layer, and a metal sealing member bonded to the metal layer, the sealing member being made of a metal <PICT:0940971/C1/1> <PICT:0940971/C1/2> which is substantially more ductile than the metal layer and the bond between the sealing member and the metal layer being a non-melt pressure seal.  The metal layer may be of Mo, Ta, Zr, Cb or Ti; the sealing member may be of An, Ag or Cu.  A protective layer of An or Ag may cover the metal layer and a priming layer on the quartz member, when the metal layer is of Mo, may be of Ti, Cr, Zr, Cb, Ta or of molybdenum disilicide.  The thickness of the coating is preferably no grea terthan 5,050 Angstroms. As shown in Fig. 2, a quartz window 20, to be joined to a copper end wall 19 for a cavity resonator of an electron gun, has priming layer 24 of Ti, metal layer 23 of Mo and protective layer 25 of gold which is joined by pressure seal to the sealing ring 26 of gold.  The ring 26 is then brazed to a gold ring 27 which in turn is brazed to the copper end wall 19. To strengthen a heavy structure, a quartz backing ring 30 joined by pressure seal to the ring 26 and with layers 23, 24 and 25 of Mo, Ti and An, respectively, abuts the wall 19.  The metal layers are deposited by cathode sputtering or by vapour deposition.  The rings 26 and cylinder 20 are sealed in apparatus shown in Fig. 7, the structure being placed between clamping heads 95 and 96, clamping head 96 having three tension rods 97 passing through head 95 and secured in slots 99 in a base-plate 90.  Clamping head 95 is carried by the piston rod 92 of an hydraulic cylinder 91 on base 90 and the heads 95, 96 are enclosed in an oven 100, heated to bring the quartz cylinder 20 to a temperature between 600 DEG  and 800 DEG  C., the piston rod 92 then forcing the heads 95, 96 towards each other, a pressure of about 2000 p.s.i. for about 10 minutes being sufficient for sealing. Specifications 768,596 and 940,972 are referred to.ALSO:<PICT:0940971/C3/1> In the making of a quartz and metal seal, the quartz is provided with a metal layer by vapour deposition or cathode sputtering to give a thin coating of fine particles of one or more metals. A quartz cylinder 20 to be metalized, before joining to a gold member, is supported by spring biased arms 38 on a rotatable shaft 37 mounted in the end wall 32 of a vacuum tight container 31. Insulating plugs 40 in the opposite end wall 33 carry a heater coil 48 and to one side, molybdenum wire 41 carrying a small bead of titanium 42 and at the other side, molybdenum wire 45 carrying a coil of gold wire 46  The wire 41 has a short length of molybdenum wire 43 wrapped round the bend in the wire 41 alternated with a short coil of tungsten wire (not shown) to prevent beading of the wire 43.  Inside and outside of the quartz member 20 are coated with a removable protective substance so that metal is deposited only on the end.  The heater 48 brings the quartz up to a temperature of about 800-900  DEG C. and the wire 41 heated to vaporize the titanium bead 42 to give a layer of about 30-50 angstrom units and then the current increased to vaporize the coil 43 to give a layer of molybdenum which is then covered by a protective layer of gold for coil 46 by heating wire 45. The primer layer of titanium may be replaced by chromium, zirconium, columbium, tantalum or by molybdenum disilicide and the molybdenum layer by tantalum, zirconium, columbium or titanium.  Silver may be used as a protective layer when the quartz is to be sealed to silver or copper.  In a cathode sputtering device, particles from an end wall connected to a negative D.C. voltage are deposited on the quartz member 20 when a gas such as mercury or kryptin is introduced into a container, the opposite end wall being connected to the positive side of the voltage source.  A small negative potential may be placed on the quartz member by coating adjacent the upper end with a removable conductive coating connected to appropriate D.C. source. Specifications 768,596 and 940,972 are referred to.