PCB
===
The HEATER11r2.zip file contains the Eagle schematic and board files as well as Gerber files suitable for use with a PCB fab house (e.g., batchpcb.com). See the enclosed README.TXT file for the files you'd want to send to a fab if you've not done that before. It will also tell you which Gerber file corresponds to what (top copper, bottom copper, etc.). Note that the board has an irregular size so this does add to the cost of manufacturing with some fabs. It's size is also suboptimal for use with Seeed's Fusion PCB service. For just one or two boards, your best bet is likely batchpcb.com unless you already have a working relationship with some other fab.

When ordering a PCB, be alert to the board's glass transition temperature (Tg). You don't want a board whose Tg is too close (or below!) the temperature you run your heated platform at. I used a FR4 with a Tg of 170. However, you may be okay with 130 or 140C. (I'm told by a fab that I use that if you keep things to 110C and you trust your temperature measurement, then a Tg of 130C is okay.)

The copper weight should be 1oz. Making it thicker will only reduce the effectiveness of the heater traces: the thicker the copper, the lower the resistance and thus less heat generated per amp of current. Some fabs which use a copper deposition process only offer 1.5oz as their lightest copper. Note that the color of the solder mask usually doesn't have anything to do with rated temperatures. You can use green if you want. (Special properties of various solder masks relate to what sort of epoxy and how much is used and how it is applied and cured.)

NOTE: the board pictured here is not exactly what is in the zip file. After producing a board, I decided to use a different Molex KK connector (the one pictured). I thus reduced the length of the tab by 2.54mm (0.1") and changed the through hole pads to be offset so that there's a bit more pad to solidly solder the right angle pins of the connector down to.

Assembly
======
With the boards in hand, solder in the SMD components. There is a good tutorial on SMD soldering at sparkfun.com,

sparkfun.com/datasheets/Prototyping/General/SolderingBasics.pdf

The resistors, capacitor, and thermistor are non-polar: you do not need to worry about their orientation. However, the LED does have a polarity. The arrow/triangle on its bottom should point towards the edge of the PCB (and be on the underside of the LED). Be careful about scratching the topside of the SMD resistors: for a number of chip resistor technologies, the coating on the top of the resistor *is* the resistive material. Putting it on the bottom of the resistor hinders heat dissipation and, in most applications, chip resistors aren't left where they will come in daily contact with something which might damage them.

I've noticed that the official MBI heater boards I've received from MBI have solder added to the two large, unused SMD pads near the thermistor. While that could just be a consequence of the stencil used to apply the solder paste during manufacturing, I've gone ahead and put down some solder on those pads in my build. That on the off chance that they are intended as a heat capacitor/resevoir to smooth out fluctuations in the readings from the thermistor.

For the recommended Molex KK connector, you will need to change the orientation of the locking tab. To do so, use some pliers and remove all 6 of the pins. Then re-insert the pins but rotated (around their long axis) by 180 degrees. You want to be able to insert the pins from the bottom side of the board BUT have the locking tab towards the top side of the board. See the third supplied photo for clarification.

If you are concerned about the exposed contacts on the top side of the board, then file them down a little and put some Kapton tape over them. Or, if you want some additional overkill in securing the Molex connector, use some JB Weld or other epoxy which can take the heat. Put plenty on the underside and then some on the top side as well over the pads: it'll be just like solder mask which is an epoxy as well. Then, because seeing those contacts may still offend you, put some Kapton tape over them.

Ordering Parts
=========
For the electronic components, use SMD 1206 size packages. If possible, stick to automotive grade (or better). Automotive grade is meant for hot, nasty environments. Also, I stuck to higher wattage resistors (1/2 W) as they are a bit tougher as regards not derating too fast as the operating temperature rises. However, it's always good to check out the data sheets before buying. Below are some Mouser and (Digikey) part numbers for the components I used. You only need one of each part. Note that if you do not use an ABP, then you can omit the 0,1" pitch pin header -- HDR2 -- which is used to connect the belt motor on the ABP. When ordering, get a flux pen if you don't already own one: fluxing SMD pads before soldering to them is generally a good idea (e.g., Mouser part number 533-0951; a no-clean flux dispensing pen; Digikey presently only carries flux syringes). Finally, if you're inclined to use high temperature solder, then be careful. Some of the high temp solders with silver have melting temperatures at or above 420C -- you can cook your diode and possibly the thermistor as well if you hold them at those temps for too long (measured in seconds).

Part - Mouser Part Number (Digikey Part Number) - Description
HDR1 - 538-26-61-5060 or 538-26-64-5060 (WM5239-ND) - Molex KK 0.156" conn., right angle
HDR2 - 571-9-102974-0 (A32704-40-ND) - 0.1" pin hdr, right angle (use 2 of the 40)
R1 - 71-CRCW12064K70JNEAH (541-4.7KUACT-ND) - Resistor, 4.7K 0.5W
R4 - 71-CRCW12061K00JNEAH (541-1.0KUACT-ND) - Resistor, 1.0K 0.5W
R29 - 71-NTHS1206N1N1003JE (541-1145-1-ND) - Thermistor, NTC 100K
C1 - 80-C1206C104K3H (445-2521-1-ND) - Capacitor, ceramic 0.1uF 100V
LED - 645-598-8210-107F (350-2048-1-ND) - LED, red/orange clear

An alternative LED -- clear red -- is 160-1457-1-ND. I used the one listed above as I had some on hand.