Prototype PCB fabs

Introduction

Having spent the last few years building wireless sensor devices for a UK research center (and some personal projects) I have found myself with a large collection of PCBs from many of the popular (and less well known) PCB fabrication services. In the hope that others will find my experiences useful I have gone through some example PCBs from the different factories I have used (and a few additional ones kindly provided by Paolo from Robomotic).

The pictures are all taken from a similar distance so can be compared in the original image available by clicking on the image (the in-article images are scaled).

Terminology & Notes

• Surface treatments:
  • HASL (hot air solder levelling, the cheapest surface treatment but doesn’t offer a very level surface… Not good for QFN or BGA packages)
  • ENIG (Electroless Nickle Immersion Gold, my preferred treatment for soldering small packages; very level surface and no tarnishing if the surface is done well, though solder wetting is not the best)
  • Immersion Silver (popular surface treatment with the European fabs, level surface, good solderability, can tarnish with time)
• Via annular ring is the remaining ring of copper around a via drill. It is best to leave a good amount of remaining ring around via drills to allow for lax alignment of drills to copper layers.
• A good minimal drill size to use is .3mm (many factories either don’t support smaller drills or will charge extra). For some of the cheaper Chinese factories, it is acceptable to use very narrow annular rings in order to keep the drill size at .3mm (for a BGA fanout for example).

Seeed Studio ($)

Seeed Studio offer a very low-cost PCB service (starting from $9.90 for <5x5cm boards) by combining multiple orders into a group order with one of the Chinese-speaking factories. ENIG surface treatment is available for a reasonable $15 surcharge.

A SNES controller to USB iPad converter board using ATMega32U2. Simple specs executed well. Good registration of all layers (copper, solder mask, position print, drills on both sides).

A simple board with tiny via annular rings (courtesy of Paolo at Robomotic). Excellent drill alignment.

iTead Studio ($)

iTead Studio offer a very similar service to Seeed Studio with the distinction of offering 4-layer boards starting from $65. Sadly, the 4-layer service only offers HASL surface treatment (I have emailed them in the past about this but unfortunately they don’t seem to think it’s worth their while to offer other surface treatments; as far as I’m concerned, if I’m doing a 4-layer boards I’m also likely to be doing QFN or BGA packages and HASL is not a good idea).

 

A tiny, tiny board executed well (not the best drill alignment on the larger drills, but adequate). I noticed that after they delivered these boards they added a note to please keep the PCBs above a minimum size (sorry for any hassle iTead )

DorkbotPDX (now OSH Park) ($)

OSH Park‘s PCBs are instantly recognisable based on the purple solder mask and ENIG surface treatment. Excellent cost for getting a few boards made. Probably the best price for 4-layer ENIG boards (but shame that 1.6mm is the only thickness available, and 4-layer boards have a very long turn-around time).

Another board courtesy of Robomotic. Very well-made PCB with excellent alignment. I personally prefer V-Cut panelisation though some people are affected by the fibres at the V-cut edge so there is something to be said for this style of tab routing.

VPCB.CN ($)

VPCB are one of the “Chinese-only” factories in Shenzhen. Excellent prices especially if you need quick turnaround (delivered to Shenzhen…). Thanks to help from a Chinese-speaking friend, they delivered to the UK using DHL (shipping cost twice as much as the PCBs, of course) which arrived in just two days.

A fairly simple board though there is a .4mm pitch QFN. Excellent alignment. Some of the boards showed signs of dust present in the production environment (specks under the solder mask, and a little copper “spike” on one of the copper planes on one of the boards). Most embarrassingly, a battery contact on the bottom (free of solder mask) showed obvious finger print marks. PCB fab workers really ought to wear gloves when handling PCBs…

HQPCB.COM ($)

HQPCB is another Chinese-speaking factory mentioned by Zach Hoeken (thanks for the PCB Assembly Spec Document, which I adapter). As described in my previous article, I ordered a batch of panelised PCBs from them using ETO for mail forwarding.

Sadly, they ignored the panelisation instructions I included (though it appears they wanted to use routing rather than V-Score for the horizontal cuts which is arguably justified given the shape of the pieces). The factory ask you to supply a mobile phone number for any questions they may have, so likely they were not able to reach me to confirm the changes they decided to make. They chose to use 5mm panel headers (I had specified 10mm which I would consider standard) which resulted in weakened tooling holes, one of which broke off on the top-most PCB. A very narrow header like that could also result in issues during pick&place (especially when it leads to issues with the panel strength like in this case).

The boards also showed signs of dust present before solder mask application (a little piece of fluff being particularly noticeable). It appears that some of the very low-cost factories may be a little lax with their cleanliness standards. There was also some sign of “bubbling” on the solder mask (again likely due to rushed processing). All the same, the pricing and speed are fantastic for prototype boards and cosmetic issues like these don’t matter for prototypes.

PCBCart ($$)

PCBCart are a well-known Chinese factory offering good-value PCB service (PCBA is available on request). Based on my experience they use different production lines based on the specs required by a specific order.

A really well-made board with excellent alignments.

A very l0w-spec board. Interestingly, the position print was executed with traditional photo-plotted silk-screen rather than the “ink-jet” method used on other boards from PCBCart, leading me to the conclusion that they operate a special “low-spec” line with older production equipment.

I chose a white solder mask for this 4-layer high density board, however peeling of the solder mask can be observed around several of the QFN packages. I now avoid unusual solder mask colours unless there is a good justification for them.

In contrast, this board with matte black solder mask (required for the visual appearance of the final product) showed no issues. Position print is slightly mis-aligned however.

Storm Circuit ($$)

Storm Circuit offer a wide range of PCB services (also PCBA) at reasonable prices. Quotes are generated based on gerber files submitted. Good for fast turn-around 4-layer PCBs with higher specs (BGA, ENIG etc). Can turn around a 4-layer board in 5 working days including delivery.

An excellent, panellised high-density 4-layer board. Very good alignment especially with regards to the vias (.2mm) in the BGA fanout. Quality from Storm has been very consistent across multiple orders.

PCBTrain ($$$)

A pool service offered by Newbury in the UK. Good range of options for a European service and reasonable turn-around times. Standard finish is immersion silver. ENIG available.

An ENIG surface board from PCBTrain (this board is several years old so may not be representative of current boards). The challenging .2mm vias were handled very well.

Another 2-layer board with very small via annular rings. No problem for PCBTrain though.

PCB-Pool ($$$)

Another pool service  operated by German (I think?) company Beta Layout with fabs in Ireland and Germany. Good range of options and good turn-around time. Via specs are a little restrictive.

A very old board (courtesy of Robomotic). Not useful in terms of evaluating the current quality of their boards but an interesting example of the tarnishing of certain chemical silver/tin surfaces (I’m not certain what treatment PCB pool used at the time).