Guide for PCB prototyping

Sometimes, it is easiest to start without a PCB. You skip the time for producing a PCB and dive straight into prototyping: see deadbug prototyping section for details. 

For a two layer fast prototype see what are our capabilities and how to order a PCB in the in-house PCB prototype section. 

If you need an advanced PCB manufactured see the professional PCB prototype section. 

If you are not sure how a circuit will work, we suggest you start with a fast prototype. This technique works best for small parts of your circuit, e.g. only one IC. 

A PCB substrate is a good mechanical support. Place any ICs that you have with pins sticking up and glue the ICs to the PCB. You can use the copper on the PCB as ground. If you need an isolated power or signal line you can glue a thin PCB strip or scratch a trace in the supporting PCB. 

More inspirations in the links below: 

• Instructables: Dead Bug Prototyping and Freeform Electronics
• Youtube: Techniques and Strategies for Building Electronic Circuits

Altium

Altium is a premium PCB design software for Windows. Download the latest version from Altium's website and install it according to the installation guide.

KiCad

KiCad is free, multi-platform, open-source PCB design software. KiCad download

 

We have a LPKF E44 mill for making PCB prototypes. It can make single and two-sided PCBs with clearance down to 0.2mm. Standard PCB thicknesses are 1.0 and 1.6mm. 

Two-sided PCBs

One limitation is that the through-hole pads and vias are not metallised! Your PCB editor will assume they are. This means you need to take additional steps when designing and soldering the PCB. 

The simplest solution is to only connect traces to your component on the bottom layer. No additional steps are necessaty. 

If you need to connect a trace on the top and bottom layer you will need to solder the terminal lead on both sides of the PCB. It is easy e.g. for through-hole resistors. It can be very hard e.g. for big capacitors. Soldering the component on both sides makes it harder to remove it later. 

Vias can be simulated by soldering a thin wire on both sides of the PCB. This is very tedious so limit the number of vias that you place in your design. 

Holes

We only have metric drills with 0.1mm step. The smallest hole we can make is 0.Xmm. The biggest one is 2.0mm. Bigger holes are possible but they will be milled, not drilled. 

Limit the number of hole sizes you have in the design. Each hole size requires a new drill bit to be installed manually. Ideally limit yourself to two-three sizes dependent on your design. E.g. 0.5mm for vias, 1.0mm for headers and 1.8mm for transistor pins. 

Through-hole plating

Top and bottom sides of the PCB can also be joined with rivets. A rivet will connect top and bottom copper and there will still be a hole where you can place a through-hole component leg. This is a bit tedious and so use it when you really need it. 

We have a Bungard Favorit hand press for through-hole rivets. We have two sizes of rivets: 0.6 and 1.5mm. These are the internal hole diameters. They require a hole of 0.8 and 2.0mm diameter, respectively. Use the small one for tricky vias; the small rivets are hard to install. Use the big ones for e.g. DC-link capacitors legs where it is crucial to have copper flood on both top and bottom sides of the PCB. 

Suggested PCB design parameters

• Minimum clearance: 0.2mm
• Minimum trace width: 0.4mm
• Minimum annular ring: 0.4mm
• Recommended annular ring: >0.8mm

A big annular ring is recommended due to the mechanical robustness of the pads. Small annular ring with no hole metalisation causes the pads to be very fragile.  

Milling copper takes time and wears the milling tool. If you have a PCB with a single trace we will, by default, only mill a thin line around the trace and leave the rest of the copper. If you need to actually remove all the copper please inform us about it. 

Steps for producing a PCB prototype

You will need to design your PCB in Altium, KiCad or similar software. Remember to minimise the number of hole sizes, as described above. Generate Gerber and drill output files, zip them all and email them to Walter. You need to supply at least top and bottom copper layers and board outline layer. 

Altium

File → Fabrication Output → Gerber X2 Files

Gerber X2 files include all necessary copper layers and drill locations. 

You will need to design your PCB in Altium, KiCad or similar software. Generate Gerber and drill output files, and zip them all. You need to supply: paste, solder, overlay layers for top and bottom and all copper layers. Gerber files are just dumb image masks so all the information about PCB stackup is not included in the files. 

We order PCBs from multiple suppliers: PCB Way, AllPCB, JLCPCB, TsPCB. They provide cheap low-quantity prototype service. Two and four layer boards that are smaller than 100×100mm cost almost nothing. Typical turnaround time is around one week. Orders from China need to go through customs. It will add 2-3 days plus VAT and customs duties. 

Make sure your PCB adheres to the production capabilities of the chosen fabrication house. 

Talk to your supervisor about ordering the PCBs. 

Before ordering components please check what we have in stock. We have components in the blue drawers in the lab and some in Walter's office. We have a very wide selection of passive components: resistors, capacitors and some inductors in both through-hole and SMD versions. SMD resistors and capacitors are in Walter's office in book kits. 

We have a selection of Würth design kits that include SMD resistors, capacitors, inductors, ferrite beads, common mode chokes and power terminals. These are free refillable by Würth so please use them. 

Additional components can be ordered as a part of your student project. The section pays for these components. CC your supervisor so we know which section pays. 

If your project is done in collaboration with a research project that project will typically pay for the components. CC your supervisor so we know which research project pays. 

Send a plaintext component list to Walter. The list has to be structured in a specific way:

RS:
679-1563, 50
679-0566, 50

Farnell:
245345, 5
565702, 15

Digikey:
HM1531-ND, 2
C2M1000170J-ND, 8

When ordering from Mouser please put your components into a basket and export the order as PDF (with prices in EUR) and email the exported file. 

Suppliers

Aalborg University has a purchasing agreement with RS components. They are the default supplier for the electronic components. If the components are not available there please look at different suppliers in this order:

1. RS components (default supplier, next day delivery)
2. Farnell (next day delivery)
3. Mouser (US warehouse, three days delivery)
4. Digikey (US warehouse, three days delivery)

For each component, make sure that:

• You are above the minimum order quantity (sometimes you can order e.g. minimum 50pcs).
• You order a required multiple (sometimes the supplier will only sell in multiples of 50pcs; you cannot order e.g. 75pcs).
• The required number of components is in stock.
• The component is not obsolete.