The purpose of this article is to review a few PCB prototype manufacturing houses that I have used in the past and that I am currently using for various projects. It does NOT cover fabrication houses that I have only heard of, and it will reflect actual experiences.

PCB-Pool
Website: http://www.pcb-pool.com/ppuk/index.html

The first manufacturing house that I want to mention is PCB-pool. It can manufacture PCBs with up to 6 Layers, but I have only used them up to 4 Layers. The minimum area for a prototype order is 1 square dm, and you can actually panelize on it several of your designs, if you want to. In case your design is smaller than that, they will multiply you and still charge you for 1 square decimeter. As an example, a 2 layer PCB, 160mm x 100mm, solder mask on both sides and silk-screen on the top side only, standard 1.6mm PCB thickness with 1oz copper weight: it costs about 85 EUR, shipping not included.

One of the best features of their website is the online quotation system, which may be accessed here:
http://www.pcb-pool.com/ppuk/order_productconfiguration_js.html

You may enter here all the variables which make up the configuration of your PCB, and they can instantly provide you with a quote. Fortunately, they actually do follow the quote and I have had several successful runs with them where the charged amount was identical to the initial quote. This online quotation system is a very good service, but it tends not to be an advantage anymore because more and more manufacturing houses offer similar online services (it slowly becomes a big disadvantage for manufacturing houses which are unable to service such a website).
A very good thing about PCB-Pool is that they have very well specified technical data about what they can manufacture and what they cannot. The link below opens a webpage where you can find spacing rules, drilling tolerances, material specifications etc. It is a quite well documented set of rules:
http://www.pcb-pool.com/ppuk/service_specifications.html?PHPSESSID=37302...

Just to sum up the most critical ones:
• minimum track width: 0.15mm
• minimum space between tracks: 0.15mm
• minimum drill size: 0.3mm (maximum is 6mm)
• smallest annular ring on vias: 0.15mm (which actually allows you to have very small vias: 0.6mm diameter in total (0.3mm drill + 2 x 0.15mm annular ring) – suitable for high density designs)
Even the layerbuilds for 4 and 6-layer PCBs is already specified, allowing you to estimate characteristic impedances for critical tracks on the PCB.

All in all they are great in terms of quality and lead time (they can get a proto made in less than 2 working days!), but you will have to pay for this significantly more than with other cheaper houses. Still the price (which they advertise as 48EUR/square decimeter) is affordable if you have a hobby project which might also put a buck or two into your own pocket. A drawback for PCB-pool is that the PCBs are literally made in Ireland (not quite a low-cost location, if you know what I mean – and they tend to overcharge you for any additional tasks, like panelizing several of your designs on one panel, or routing the boards once finished etc.). This also adds to the shipping cost which can be quite high. It was fine when I was living in Ireland and the charge was about 10-15 EUR, but if I want to have something shipped to me know, in Romania, the shipping cost would easily be more than 40 EUR (still through courier, which would make great delivery timing, I am sure)
Strongly recommended due to lead time and quality!

Olimex
Website: http://www.olimex.com/pcb/index.html

These guys are from Bulgaria. Not really my favorite place in the world, but they get the job done and they do it really cheap! They only charge 30 EUR for a 160mm x 100mm double side PCB, with soldermask on both sides and silk screen on top side. There are some small overcharges if you use, for instance non-standard drill sizes (the standard ones are clearly specified on the website) but these are very small, and Olimex is still the best PCB prototype manufacturing house I have used in terms of pricing. They also have the advantage of having a quite good webpage with technical specifications (although not as complete as PCB-Pool, but still allows you to have an Olimex - producible design without asking additional technical questions): click on the “Technical Info” tab at the link provided above.

Just to sum up a few of the rules:
• minimum track width: 0.203mm
• minimum space between tracks: 203mm
• minimum drill size: 0.6mm (maximum is 5mm)
• smallest annular ring on vias: 0.203mm (which actually allows you to have vias no smaller than 1.006mm diameter in total (0.6mm drill + 2 x 0.203mm annular ring))

Be warned that also Olimex has a minimum PCB area/order constraint, the smallest panel being 160mm x 100mm (for both single side and double side PCBs). However, they are so cheap that they make it worth pay the entire panel price even if you do not need more than one small PCB.

Another advantage in terms of pricing is that they also offer the possibility of shipping through airmail (which is not courier, and does no provide a tracking number, but is dirt-cheap). For small parcels, Airmail charges 5.5 EUR for shipping anywhere in Europe, and it only gets up to 8.5 EUR outside the continent. Not being a courier, they do not guarantee delivery times (it can be anywhere between 1 week and 3 weeks, but I was fortunate so far and got the parcel in just 1 week).
The quality of their PCBs is also very good. The finish is Ni-Au which both looks good and is very good for soldering. And what impressed me most was the quality and resolution of the silk screen. They do not specify minimum text size and thickness, but I have used 0.125mm thick text with great results! Too bad they do not make 4 layer PCBs.
Strongly recommended due to pricing and quality!

BatchPCB
http://www.batchpcb.com/

These guys are from the USA, so they charge USD, rather than EUR, which is a good cost reduction now-a-days, when the exchange rate is the way it is. The price is good, and they manufacture both 2 layer PCBs (2.5USD/square inch) and 4 layer PCBs (8 USD/square inch). On top of that there is a small 10 USD handling charge which is constant no matter how large or small the area of your design is. But what is great about BatchPCB is the minimum PCB surface that they accept: 1 square inch (imagine a rectangle of about 2.2mm x 3mm). This means you can have designs as cheap as 12.5 USD (shipping not included)

The best feature of BatchPCB is their online DRC. The automated website allows you to submit the zipped gerber files and it will automatically perform a check to see if they comply with the manufacturing rules. The result of the check is sent to you by e-mail in a few minutes. So in case you receive a positive response, you are quite sure the design is manufacturable. It is really impressive!

This is what makes them very efficient for high density designs. Also the design rules are pretty good, although they are different between 2 layer and 4 layer boards:

• 2 or 4 layer boards - 0.062" FR4 material
• 2 Layer sizing:
o 8mil (~0.2 mm) spacing minimum
o 8mil (~0.2 mm) traces minimum
o 20mil (~0.5 mm) minimum drill size

• 4 Layer sizing:
o 6mil (~0.15 mm) spacing minimum
o 6mil (~0.15 mm) traces minimum
o 13mil (~0.33 mm) minimum drill size
o No blind/buried vias

• 500mil (~12.7 mm) maximum drill size
• Soldermask both sides
• 1oz Copper

The way BatchPCB works is by gathering several designs from many customers, by panelizing the designs and then by manufacturing them at a low-cost PCB manufacturing house in China (http://www.goldphoenixpcb.biz/). These Chinese are good in terms of pricing, but even they would not deal with a customer who would like to manufacture a 1 square inch PCB. BatchPCB however, manages to meet the minimum order area of the manufacturer by putting together several designs.
Of course, this has a negative impact on the lead time, as it cannot really be guaranteed. It will always depend on how fast a panel gets put together, and this, in turn, depends on how fast people apply for a spot in the panel. But, generally speaking, they gather pretty fast. Once the entire panel is manufactured in China it is shipped back to the USA and the BatchPCB guys depanelize it and spread it around the world through separate dispatches. The advertise lead-time is 3-4 weeks. I have had a 4 Layer PCB shipped to me after only 19 days after submitting the gerbers.

In terms of shipping options, you can always pick the fast, sure and expensive way, which is through FedEx or a similar courier, maybe. However, this will, have a negative impact on the overall cost of your design. Fortunately, BatchPCB also ships through US Postal Service. They have the reputation of being quite bad at international shipping and BatchPCB explicitly advises against using USPS for international orders. But, if you are looking for cheap design, if you feel a bit lucky and if you are in no hurry with your design, it is a real option. This is what I used and I benefited from two 4 layer PCBs at the total cost of an amazing 54 USD (about 40 EUR) with shipping included.
Strongly recommended due to pricing and minimum accepted area!