Antennas and Microwaves
CUTTING THE BOARD
In terms of ease of use, another good feature of the RO4350 material is that the 0.76mm material and thinner can be cut to size using a descent pair of scissors. No need for guillotines or band saws.
SCORING THE COPPER (Manual Method)
The simplest and cheapest method of scoring is just to do it by hand using a sharp modelling knife. To mark out the design it is best to print the layout from a drawing or CAD package that can produce an accurate 1:1 scale image. Modern inkjet printers are incredibly accurate, so no need to worry about the printer end of things. If you are planning on any vias or fixing holes it is worth including them on the drawing as well, mark the centres with a cross.
Having printed the layout on normal paper, fix it to the board using “3M Spraymount” (available from most stationary shops) . It is best to spray the back side of your paper layout, let it dry for a few minutes and then press it firmly to the board. This way there will be less adhesive to clean off your board later.
Now, with the aid of a good steel ruler, score through your design taking care to not to miss any edges. It is easiest to make 2 or 3 light cuts than try to cut through in one.
The aim is to just start to break through the copper layer, the ceramic loading of the board makes it very abrasive so you don’t want to cut into the board too much or you will get through a lot of blades. For the holes, mark the centres using small centre punch or scribe.
Once you are sure you have scored all the lines and centre punched all the holes, remove the paper layout. Any remaining adhesive can be removed from the board using alcohol based cleaner or just hot water and detergent.
Fix the design to the board and trim to size.
Score carefully using a modelling knife and steel rule.
PCB Prototyping
Page 2 of 5
DRILLING AND PEELING
At this stage any holes will need to be drilled because once the copper is removed the hole centres will be difficult to find. Before drilling it is also helpful to circle the hole centres with a marker pen, the small punch marks are easy to lose in the drill dust.
To drill the holes you will unfortunately need proper Tungsten Carbide PCB drills, standard HSS drills are blunted almost immediately by the ceramic loading in the board. The drills are now readily available from a number of sources (see below), they are best run at high speed in small modelling drill such as a Dremmel or similar.
Sources for TC PCB drills :
Type “Gloster Tooling PCB drills” into Google and you should find their Ebay shop. I ordered though them and found them to be very polite and efficient.
Axminster Tools UK, again just type them into Google, they have a good selection general workshop equipment as well.
