Sunday, 02 July 2017 11:18

How to build a BGA profile from scratch

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These instructions do not cover the basic usage of the scotle/BGA Rework machine and how to program it etc.. but shows you have to make the perfect profile that you can use. Profiles are very specific to your machine and environment but there is a basic method that can be used on how to make these profiles that I have worked out and I will now show you.

My scotle is a 3 zone BGA rework machine however these instructions will work for a normal 2 zone machine. All you have to do is skip the lower HR zone bit. Also if you have an upper HR machine these instructions will work the same.

So the 3 temperatures we will need to figure out are

  • Lower IR
  • Lower HR (optional)
  • Upper IR/HR

Splifire mods recommending flatlining your machine, which basically is figuring out what your preheat ranges and temperature settings should be (at the point your top heater is initiated)

  • At chip/top of board – 160c to 170c
  • Bottom of board – 170c to 180c (200c is absolute max and should be avoided)
  • Preheating should usually take about 7 – 8 minutes. Colder climates might take longer

Other settings

  • Dark IR (IR) – ramp rate should always be 1.00
  • Hot Air (HR) – ramp rate should always be 3.00
  • The IR head should be 2.0cm to 2.5cm away from the target chip (about the height of a standard capacitor)
  • The upper HR head should be almost touching the chip, but make sure there is a gap so the air can escape.
  • The lower HR head should be ¼ inchi or 6.25mm away from the boards

So firstly we will prep out our machine

  • Rack a spare board (I used an old xbox 360 board)
  • Build the copperwire probe mod with an external temp sensor (I used TM-902c)
  • Put the copper probe under the middle’ish of the board (as per video) – A good green bit to prevent thermal welling.
  • Put an temp probe (small type ie.e the scotle one) under the target chip

Notes for testing

  • Try and do all of these tests/trials at the same time so you have the same room temperature as this can affect things
  • After each run make sure that you allow you BGA machine to cool back to the ambient temperature (same as it was for the first run) this gives you the same starting point
  • The readings from the TM-902c are always changing. I think these devices are very accurate and do not average the result before it is put on screen like some temperature sensors so the temperature shown is always changing within a range. So the result I write with this device are going to be higher than the average at that time. This effect could also be caused by the pulse nature of the lower IR plates, I would have to check this.
    • You can use a K Type USB logger to draw a graph which will give you much better results and easier to interpret and should be less erratice
    • You can use a temperature sensor device that shows average results (multimeters usually do this or the one in the spitfiremod videos {add model here)

Lower IR

  • Run each the scotle at each of the defined Lower IR values below, not forgetting to cool down before each run so you have the same baseline for each run.
  • As you are running note down the time taken to reach each of the lower board temperatures.
  • I run these for 20 minutes so I can definitely see the max temperature reached. Most reflowing/reballing should not take 20 minutes.

NB: johnnyx method usesthe scotle main probe on the top of the motherboard for the temperature (of 180c) and sets the upper IR to 0c long dwell, he also sets the lower HR to match the lower IR and then gets the temperature needed. This puts at risk the board as you do not know what temperature the lower componenets are exposed to. This method is probably ok for naked boards like the xbox 360.

Instructions

  • Set the first temperateure (180c) onto the lower preheat panel.
  • Get your stop watch ready
  • Check you temperature sensors are on
  • Turn on the preheat and start the stop watch
  • Fill in your table as things progress

You could use the profiles for the Upper IR/HR and Lower HR and set them to 0c and a large dwell time so you could use the inbuilt temperature probe, but the reason I have not is that the Lower HR on mine will always kick out air and if it is not heated it is cold which could affect my profiling. By getting just the IR preheated temperatures first I can find out what is safe.

NB - sort

  • I would not go above this because there is a +-10c shift in the scotle preheater and anything over 200c is dangerous. However if you are careful you might go higher when needed.
  • Try probing at different areas to see how much difference there is, this is especially true ig you are using a lower HR and you can probably afford the temperature to be lower in the tareget temp ie.e. 170c because when you use the lower HR it will compensate for this.
  • The larger plates of the scolte might be a lot hotter than the middle little plates.
  • The splitfire guy said it should come to temp 7-8 minutes, so if it takes ages you might need to notch up the heat a little bit (5c steps)
  • Times taken to reach bottom board temperature just by IR plates on my 3 zone sctole
  • Probe is in the middle’ish and on an unsurrounded green area, right in the middle of the plates. Add picture
  • For those who have notice that the lower HR (if you have one) is not turned on this is on purpose. I want to find out the temperatures developed by the lower platesd first. Yes there will be a lower temperature above the lower HR section.
  • The TM-902c is very flicky, not the main probe. My results are when that temp is first hit, not average.
  • The logger would give a better profile because it is using a graph and probably averages it mnore.
  • These results are just for safety and part of the HR profile ? not sure about this statement
  • The lower IR heaters are only on or off and uses pulsing to get the correct temperature? So this means with the heater curve is similar until required temperature is reached as the plates are either on or off. – this might not be true
  • There is some natural variability in my results because I am not using 100% lab conditions

 

Now

A table showing when the lower board Temperature Reached was reached (mins) and what the Lower IR presheater were set at.

Room:     c
Board:     c

Lower IR Temp

180

185

190

195

200

210

220

225

Lower Board Temperature

                 

140

                 

145

                 

150

                 

155

                 

160

                 

165

                 

170

                 

175

                 

180

                 

185

                 

190

                 

195

                 

200

                 

205

                 

210

                 

215

                 

NB: make a note of the room temperature and lower board temp before you start.

My actual results

Room: 20c
Board: 23c

Lower IR Temp

180

185

190

195

200

210

220

220

2nd

225

225
2nd

Lower Board Temperature

                     

140

 

3:57

3:24

3:45

3:50

2:32

3:38

2:88

2:24

2:20

3:27

145

 

4:08

3:45

3:52

4:05

3:48

3:46

2:35

2:27

2:24

3:38

150

 

5:08

3:55

5:04

4:59

3:54

3:50

2:42

2:45

2:27

3:48

155

 

6:34

6:12

6:13

6:16

4:08

4:00

3:48

3:48

2:37

4:47

160

 

7:50

6:23

7:39

6:22

5:11

5:11

5:04

3:53

3:53

4:55

165

 

11:34

7:39

8:53

8:44

6:28

5:22

5:24

5:17

3:59

5:08

170

 

13:15

8:51

11:30

9:04

7:37

6:56

6:27

5:20

5:09

5:16

175

 

18:14

10:36

13:51

11:22

9:09

8:02

6:30

5:42

5:22

5:21

180

 

-

15:00

14:00

13:08

10:31

10:58

6:38

6:56

5:42

7:47

185

 

-

-

-

17:14

15:51

13:32

6:42

7:07

9:19

9:56

190

 

-

-

-

-

19:11

16:21

11:24

10:19

9:34

11:15

195

 

-

-

-

-

-

-

12:28

12:18

12:48

12:25

200

 

-

-

-

-

-

-

15:17

15:48

17:44

14:09

205

 

-

-

-

-

-

-

-

17:40

18:55

15.28

210

 

-

-

-

-

-

-

-

-

-

18:34

215

 

-

-

-

-

-

-

-

-

-

-

Notes -

  • If the temp mod is done, temp results would be more constent
  • The lower HR nozxle size can affect temp (when dealing with lower HR config)
  • Your preheat is what compensates for your environment amnd machine for the most part. Once your profile is configures olny the preheat section (time and temp) would need to be changed depending on the environment and possibly the board you are working on
  • Pick a run and then set the top IR to off
  • The board above larger plates might get hotter
  • These results would be better from a graph
  • Try an use the lowest IR temperature to get you to the desired temps


 

Choose you lower IR temperature

You results are now in. We are looking for a Lower board temperature of 170c/180c in about 7 – 8 minutes. Now this is a guideline so If yours are slightly out don’t worry too much. If you are using a 3 zone machine you can get a away with 170c because your 3 zone (lower HR) will more than compensate for this.

When looking at the table you can see that all of the runs have the same sort of profile, they heat up rapidly and the slow right down when they get to about 75% max temp of the run, they then eventually hit the max temp and stay there.

My results above are the times when the temperature on my TM-902C reached that value. This is most likely at the top of the range of the actual temperature. I on avergage so a range on about +-10c so I would know off 5c off the tempratures reached and then use those. This might not be the case for the temperature senor you use especially if the result on screen is steady.

This means I will use 210c as it reaches 170c @ 7:37 mins. It should be noted that the max temperature for this run is 210c which is 10 degrees below the dangerous 200c.

On a warm day I might use 200c. It should also be noted I am in the north of England and it is cold,and I am using the scolte unmodified (i.e. the spitfire lower IR temp mod)


 

Lower HR profile(preheat only configuration) – if present

Before I start this section I need to tell you what a 3rd zone or lower HR heater is for. If you don’t have one you can skip this section

  • With this 3rd zone so you can deliver high tempreatures to a single chip like the playstation CPU where there needs to be a lot of heat delivered to the CPU for a successful lift but you do not want this heat going into the other components on the board because they will become damaged. These chips usually will have their own Lower HR profile which is not covered here, but I suspect it would potentially match the Upper IR/HR profile
  • We can also use the 3rd zone HR as part of our preheat process where is just set at a single temperature like the lower plates do the correct temperature is reached on the top of the board above the HR unit. This is used for smaller chips were a specific profile is not needed, preheating is sufficient. (this is what we are going to do here)

In our tests in the above section (Lower IR) we did not have the lower HR on and if we had tested the top board temperature above the HR unit, i.e. under the target chip we would have found it to be a lot lower than the rest of the board. (Literally the cold HR unit was in the way and there are no lower IR plates delivering heat to that part of the board, or definitely a greatly reduced amount.)

With this section we will use our choosen lower IR plates temp (200c) and try to findout what lower HR temperature setting will deliver 170/180c to the top of the board under the chip at the 7 – 8 minutes mark.

Instuctions

The easyway is just to set your lower HR to the same temp as lower IR plates with a ramp rate of 1

  • Set the lower IR preheat to 200c
  • Configure the Upper IR/HR to the following settings (this basically disables the upper unit)
    • L1 – 0c
    • R1 – 1.00
    • D1 – 2000
  • Configure the Lower HR
    • L1 – 180c
    • R1 – 1.00
    • D1 – 2000
  • Make sure you temperature sensors are on and your stop watch is ready
  • Start the profile and stop watch
  • Fill in the table as you go.
  • Run the profile for 20min to see what happens and what tempreatures are reached.

Run these instructions for each Lower HR temperature

Notes

  • We are looking for the top temp. we will use the main probe for this
  • Configure a preheat sgment on the upper IR i.e. mega long at 0c
  • Configure the lower IR profile to the required temp with a long time
  • R1 or R3?

A table showing when the upper board Temperature Reached was reached @ (mins) and what the Lower HR was set at. I have also added actual lower board temperature

Room:            c
Board:            c
Lower IR        c

Lower HR Temp

180

185

190

195

200

210 220 225

Upper Board Temperature

                 

140

                 

145

                 

150

                 

155

                 

160

                 

165

                 

170

                 

175

                 

180

                 

185

                 

190

                 

195

                 
  • NB: make a note of the room temperature, lower board temp and lower IR temperature setting, before you start.

My Results

Room:            c
Board:            c
Lower IR        c

Lower HR Temp

180

185

190

195

200

210 220 225

Upper Board Temperature

                 

140

                 3:46

145

                 4:06

150

                 4:29

155

                 5:02

160

                 5:45

165

                 9:27

170

                 -

175

                 -

180

                 -

185

                 -

190

                 -

195

                 -
  • NB: make a note of the room temperature, lower board temp and lower IR temperature setting, before you start.

Some notes - sort

  • make sure probe is clean and touching
  • moving the HR head does not seem to make much of a difference
  • moving the unpper IR does make a lot of difference after 2-2.5cm
  • running the lower HR causes a drop in temperature probably because of the air exgust blowing over the board and probe
  • on the probe table lower IR this is for noobies + to get the max delivered temp by the plates for safety
  • while experimenting aus 225 lower would deliver 160 on top of board, so johnny was right
  • chip might get hotter when you run upper IR
  • when the lower HR is on it seem to slightly lower the plate temp. must be HR exhaust
  • over time the temperaturs will creep up, however this will  follow that standard plateau graph.

Next phase - Build profile preheat segment

This will include

so at 5:45 mins the top board temperature is 160 and bottom board temperature is 160c(+/-10c) so the settings for me should be as follows:

  • Upper IR
    • L1 - 0
    • R1 - 1.00
    • D1 - 360
  • Lower IR
    • 225
  • Lower HR (if present)
    • L1 - 225
    • R1 - 1.00
    • D1 - 2000

Now build your profile

  • If 160 is not reached by step 2, increases your preheat temp. As long as you dont go into the bottom board temperature danger zone, makign it slightly longer is ok.
  • for lower IR dont set time as soon 1 is left, give it a moment. I think i meant to say here is it ok making a step a little be longer than  required to add a buffer into your profiel so you do not have to redue your profile every time. However the very last moments of your profile need to be the the same as this is the point at which reflow occurs. so adding a couplke more seconds in at 190c segment is ok but not as safe at 225c.
Read 1024 times Last modified on Sunday, 02 July 2017 12:50