George Harker

Create a new group for backwp-users for acls

Create a new s3 bucket with no public access eg <BACKUPBUCKET>

Create an inline policy for the new iam group backwp-users

{
	"Version": "2012-10-17",
	"Statement": [
		{
			"Sid": "Stmt1457967512000",
			"Effect": "Allow",
			"Action": [
				"s3:ListAllMyBuckets"
			],
			"Resource": [
				"*"
			]
		},
		{
			"Effect": "Allow",
			"Action": [
				"s3:PutObject",
				"s3:GetObject",
				"s3:ListBucketMultipartUploads",
				"s3:AbortMultipartUpload",
				"s3:ListBucketVersions",
				"s3:ListBucket",
				"s3:DeleteObject",
				"s3:GetBucketLocation",
				"s3:ListMultipartUploadParts"
			],
			"Resource": [
				"arn:aws:s3:::<BACKUPBUCKET>",
				"arn:aws:s3:::<BACKUPBUCKET>/*"
			]
		}
	]
}

Create a new user in the group eg backwpup

Create an API key for the user and note it down (it is shown only once). Supply this to backwpup (both the secret and public key). Ensure you use the correct service region for the s3 bucket.

I strongly recommend reading 1bitsquared’s blog post and This hackaday post before deciding to buy a T962A oven.

The short version is that getting these to work reliably is a /lot/ of work.

Issues Include:

  • Poor temperature profile following
  • Uneven heating causing scorching in places even whilst other areas do not reflow
  • Lack of internal convection leading to uneven heating
  • Unshielded infra red bars causing hot spots
  • Poor default firmware
  • Masking tape internally that will stink when it burns
  • Lack of grounding

However good reflow ovens are expensive. And with some work you can get these functional – even for relatively large boards. This makes them a reasonable – albeit time consuming way to get a reflow oven at affordable cost.

Several other sites (listed above) have better guides on what first steps to take.

Required mods:

  • Fix the grounding – do this first
  • Fix the masking tape and replace with Kapton – also do this before plugging in or turning on the oven
  • Flash the firmware to unified engineering’s firmware: UnifiedEngineering T962 firmware

Additional fixes:

  • Add better thermocouple interface – I used this one https://github.com/UnifiedEngineering/T-962-improvements/wiki/Better-thermocouple-interface and followed the instructions there for wiring it up
    • More thermocouples allows us to average more places in the oven. To do this I hacked the firmware to allow calibration of pairs of sensors and average them all – see my GitHub fork for T962A firmware
    • Allow thermocouples to be nearer to the PCB – this is a tradeoff. You can mount directly on the board and deal with thermocouple wires and fixing the TC to the board all the time, or you can install additional thermocouples in tubes near the board. I did the latter using threaded metal tubes usually used for lighting fixtures
  • Add additional thermocouples:
    • More thermocouples allows us to average more places in the oven. To do this I hacked the firmware to allow calibration of pairs of sensors and average them all – see my GitHub fork for T962A firmware
    • Allow thermocouples to be nearer to the PCB – this is a tradeoff. You can mount directly on the board and deal with thermocouple wires and fixing the TC to the board all the time, or you can install additional thermocouples in tubes near the board. I did the latter using threaded metal tubes usually used for lighting fixtures
    • I also put them at slightly different heights to allow for better averaging – the existing TCs are near the top of the oven and will read hotter than the board
  • Seal the front of the oven with gas grill seals so that airflow from the front doesn’t drop the temperature at the front of the oven.
  • Measure and calibrate your thermocouples against various locations on the PCB. I use this sheet here which allows calculation of calibration mapping from the MAX TC probes to probes on a PCB which are what we ideally want. I measured several locations, and select two curves for calibration which get entered into the firmware

  • Develop and tweak your own paste profiles using the same link you can develop a curve based on manufacturer instructions for the paste.
  • I can now successfully reflow boards of about 8in x 8in in solder free paste which was certainly not possible before