A diamond assembly

A bonded diamond assembly comprising:

• a polycrystalline diamond wafer having a largest linear dimension of between 25 mm and 200 mm;
• a substrate;
• a bonding layer located between the diamond and the substrate and bonding them together;
• wherein the bonding layer, when inspected using ultrasound using a resolution of 50 μm, a focal length selected to inspect the bonding layer, and frequencies of 100 MHz and 30 MHz, comprises any of the following:
• no area of 10 mm by 10 mm comprising more than 100 voids extending across the thickness of the bonding layer with a largest linear dimension of less than 100 μm;
• no area of 10 mm by 10 mm comprising more than 5 voids extending across the thickness of the bonding layer with a largest linear dimension of between 100 μm and 1 mm;
• no area of 10 mm by 10 mm comprising more than 1 void extending across the thickness of the bonding layer with a largest linear dimension of greater than 5 mm;
• no area of 10 mm by 10 mm comprising more than 200 voids with a largest linear dimension of less than 100 μm, wherein said voids do not extend across the thickness of the bonding layer;
• no area of 10 mm by 10 mm comprising more than 10 voids with a largest linear dimension of between than 100 μm and 2 mm, wherein said voids do not extend across the thickness of the bonding layer;
• and
• no area of 10 mm by 10 mm comprising more than 2 voids with a largest linear dimension of greater than 2 mm, wherein said voids do not extend across the thickness of the bonding layer.