Any soldering experts here?

[Fritz]

I'm getting ready to replace the DSP chip in a Yamaha AVR. There are YouTube videos but they're all lacking in the details like what temp to set the rework station to, etc. I've searched in vain for a written overview but have come up empty. Looking for tricks traps, advice or links to sites that cover the details. The one issue I'm in the dark about is this chip has a metal center section on the bottom that solders to a corresponding metal plate on the circuit board, I need to know the proper technique to handle this.

DSP chip -

 

[Wasmachineman_NL]

@RageBone

 

[piranha32]

I'm getting ready to replace the DSP chip in a Yamaha AVR. There are YouTube videos but they're all lacking in the details like what temp to set the rework station to, etc. I've searched in vain for a written overview but have come up empty. Looking for tricks traps, advice or links to sites that cover the details. The one issue I'm in the dark about is this chip has a metal center section on the bottom that solders to a corresponding metal plate on the circuit board, I need to know the proper technique to handle this.

If you have no experience in working with SMD chips, I recommend to practice first on scrap boards.

If the chip has no metal pad underneath, removing the IC is a pretty simple job. For desoldering, get some good flux and Chip Quick solder. Generously cover all pins, in the flux and ChipQuick, make sure that the solder is liquid on all sides, and remove the chip. After removal, clean the flux with isopropyl alcohol, and clean the pads well using solder wick. Place the new chip, and solder it down. ChipQuick is a low melting point solder, which will stay liquid for long enough to heat all sides and remove the chip.

Use solder wick to clean the pads. Put the wick on the pad, press gently with soldering iron, wait until the solder melts, and drag along the length of the pad. Don't try to drag across the pads, it's too easy to damage them. Repeat until all pads are clean. Flux the pads again, put some solder on the tip, drag along the pads to wet them, and clean again.

There is a simple trick, which makes mounting the new chip a breeze: Flux the pads well, put enough solder on the tip to make a big drop, and drag it along the pins holding the tip submerged in the molten solder, but without touching the pins. Don't worry about bridging pins, you can clean bridges later. Search YT for "drag soldering".

As for temperature, for leaded solder I heat up the soldering iron to 300-320C, Occasionally I'll bump the temperature to 350C if 300 is not enough.


The operation gets more complicated if the chip has a thermal pad underneath. With enough experience it is possible to replace it with just a hot air station, but you have a very good chance of damaging the board.
I highly recommend preheating the board before the rework. If you don't have a board preheater, you can use an electric skillet. The point is to keep the board warm during the entire operation. There is a big plane of copper under the chip which drains away the heat, and it is difficult to heat up the pad through the chip to the point of melting solder.
I usually heat the board up to 150-200C before using hot air. With a warm board, a light blow of hot air is usually sufficient to melt the solder.
Once the chip is removed, clean the solder with a wick.

Soldering the thermal pad is tricky. Since you can't access it from outside, you have to put some solder on the pcb before mounting the chip, and reflow it by heating the chip from the top. It has to be the right amount of solder: too little will result in a poor thermal connection, too much will float the chip too high to solder the pins to the board, and can result in shorts. Once again. I recommend practicing on scrap boards.

I set the hot air temperature and flow rate by experimenting. Set the temperature by trying to melt a piece of solder on a sheet of paper. Flow rate has to be big enough to deliver enough heat, but not too big, to not blow other components off the board. Again, practice on scrap boards.

It is a good idea to cover components around the chip with a kapton tape, or aluminum foil.

After mounting the chip, you have to clean the board. I use a tooth brush, isopropyl alcohol, and clean water.
Start by scrubbing the board with IPA and the brush until there are no residues of the flux on the board. Rinse with IPA frequently during the operation.
After you're done, rinse again with clean IPA, and then rinse the IPA with water. After rinsing in water, rinse again in IPA and let the board dry.
Water removes the dirty IPA, and clean IPA removes water.

As you may have noticed, I mentioned flux many times. Good flux is the key to success when working with SMD components, don't be shy with it. I use Kester 186 for all my work. It is tacky, and requires cleanup after work but holds the components during soldering.

Good luck!

 

[Fritz]

If you have no experience in working with SMD chips, I recommend to practice first on scrap boards.

If the chip has no metal pad underneath, removing the IC is a pretty simple job. For desoldering, get some good flux and Chip Quick solder. Generously cover all pins, in the flux and ChipQuick, make sure that the solder is liquid on all sides, and remove the chip. After removal, clean the flux with isopropyl alcohol, and clean the pads well using solder wick. Place the new chip, and solder it down. ChipQuick is a low melting point solder, which will stay liquid for long enough to heat all sides and remove the chip.

Use solder wick to clean the pads. Put the wick on the pad, press gently with soldering iron, wait until the solder melts, and drag along the length of the pad. Don't try to drag across the pads, it's too easy to damage them. Repeat until all pads are clean. Flux the pads again, put some solder on the tip, drag along the pads to wet them, and clean again.

There is a simple trick, which makes mounting the new chip a breeze: Flux the pads well, put enough solder on the tip to make a big drop, and drag it along the pins holding the tip submerged in the molten solder, but without touching the pins. Don't worry about bridging pins, you can clean bridges later. Search YT for "drag soldering".

As for temperature, for leaded solder I heat up the soldering iron to 300-320C, Occasionally I'll bump the temperature to 350C if 300 is not enough.


The operation gets more complicated if the chip has a thermal pad underneath. With enough experience it is possible to replace it with just a hot air station, but you have a very good chance of damaging the board.
I highly recommend preheating the board before the rework. If you don't have a board preheater, you can use an electric skillet. The point is to keep the board warm during the entire operation. There is a big plane of copper under the chip which drains away the heat, and it is difficult to heat up the pad through the chip to the point of melting solder.
I usually heat the board up to 150-200C before using hot air. With a warm board, a light blow of hot air is usually sufficient to melt the solder.
Once the chip is removed, clean the solder with a wick.

Soldering the thermal pad is tricky. Since you can't access it from outside, you have to put some solder on the pcb before mounting the chip, and reflow it by heating the chip from the top. It has to be the right amount of solder: too little will result in a poor thermal connection, too much will float the chip too high to solder the pins to the board, and can result in shorts. Once again. I recommend practicing on scrap boards.

I set the hot air temperature and flow rate by experimenting. Set the temperature by trying to melt a piece of solder on a sheet of paper. Flow rate has to be big enough to deliver enough heat, but not too big, to not blow other components off the board. Again, practice on scrap boards.

It is a good idea to cover components around the chip with a kapton tape, or aluminum foil.

After mounting the chip, you have to clean the board. I use a tooth brush, isopropyl alcohol, and clean water.
Start by scrubbing the board with IPA and the brush until there are no residues of the flux on the board. Rinse with IPA frequently during the operation.
After you're done, rinse again with clean IPA, and then rinse the IPA with water. After rinsing in water, rinse again in IPA and let the board dry.
Water removes the dirty IPA, and clean IPA removes water.

As you may have noticed, I mentioned flux many times. Good flux is the key to success when working with SMD components, don't be shy with it. I use Kester 186 for all my work. It is tacky, and requires cleanup after work but holds the components during soldering.

Good luck!

Thank you sir. Very much appreciated. The new DSP chip just arrived in New Jersey from China. It shows a delivery date of June 10 but it should get here sooner. Gotta hand it to AliExpress, I've been getting daily shipping updates since placing the order.

 

[RageBone]

The one issue I'm in the dark about is this chip has a metal center section on the bottom that solders to a corresponding metal plate on the circuit board, I need to know the proper technique to handle this.

That is what @piranha32 has called a "thermal pad underneath".
In this case it simply means that you have to get everything hot enough for the solder to melt, even below the chip.

A preheater would help with that a lot, though you can also simply go a bit higher in temperatures and duration with a long time on like 200°C air temperature to soak the board.

I personally usually use around 370°C air temperature and even turn it up to 450°C sometimes if the parts won't budge soon enough.
Depending on the shoddiness of your hot-air, you need to turn heat and airflow to the max, to get anything to budge reasonably quickly.
At least that was the case for me with my first chinesium 858D.

Looking at the picture you posted, you have at the very least, one capacitor on the bottom left corner that needs protection as well as the plastic ports in the top left that would melt at such temperatures.

As piranha said, flux is very important and should not be used sparingly.
But you need to also watch out for your health.
Only do this with good ventilation and try to not breathe any of the fumes!
A fume-extractor would be very good to have and use.

Soldering the thermal pad is tricky. Since you can't access it from outside, you have to put some solder on the pcb before mounting the chip, and reflow it by heating the chip from the top. It has to be the right amount of solder: too little will result in a poor thermal connection, too much will float the chip too high to solder the pins to the board, and can result in shorts. Once again. I recommend practicing on scrap boards.

I disagree on the trickyness, or rather, i guess it depends on the sizes of the pads on the PCB and IC.
the further away they are from the pins on the edges the less of an issue.

Use solder wick to clean the pads. Put the wick on the pad, press gently with soldering iron, wait until the solder melts, and drag along the length of the pad. Don't try to drag across the pads, it's too easy to damage them. Repeat until all pads are clean. Flux the pads again, put some solder on the tip, drag along the pads to wet them, and clean again.

The one place where you really need to watch out is ripping pads off the PCB while taking the IC off and while cleaning the pads.
Best is you really try that out on dead PCBs first.

Getting the chip on later isn't that much of an issue i think.

Since you have a GND plane for heatsinking below the IC, i think that dragsoldering the pins afterwards won't really do.
Best way i can think off, not necessarily the best way:

Remove all solder from the pads.
Add leaded or even low temperature solder back to the pads
Solder everything at once and let the surface tension do the job.
It will be a bit stressfull to nudge the chip around while everything is hot and melted but you at least don't need to worry about bridges on the pins.

Just FYI, those LQFP packages suck in my opinion and it is a good idea to train soldering those pins and removing bridges from them.

 

[Fritz]

I should have mentioned that I grabbed the pic from Google, It's not my board. I'm really concerned about damaging the board with too much heat or knocking other components off accidentally. I have some thermal tape coming from Amazon today which I hope will lessen the risk.

 

[RageBone]

I should have mentioned that I grabbed the pic from Google, It's not my board. I'm really concerned about damaging the board with too much heat or knocking other components off accidentally. I have some thermal tape coming from Amazon today which I hope will lessen the risk.

I have not personally popcorned a PCB yet, you can simply get a dead board and try around on that.
Get yourself comfortable first.

Tools can help you with that, for instance i really like those vacuum suction things to pick the ICs up from the board.
But normal tweezers work very fine for that as well, just differently.

In the end, with enough bad luck or tardieness, knocking off parts around the IC is always easy.

So get yourself familiar and comfortable with your setup, tools and such things first.

 

[Fritz]

Just made a practice run on a IDE HDD controller. I started out at 300 degrees and kept increasing the tgemp until the chip broke lose. This occurred at 850 degrees, does that sound right?

BTW - It's the same type chip (physically at least) as I'll be replacing in the Yammy.

 

[Stephan]

Bit of a tangent from me, should you wreck it... my modus operandi for video and hifi has been discrete components for decades. Without proprietary DSPitis. So HDMI out from a PC running Kodi or similar and discrete high quality audio out, going into a discrete, high quality, class A amplifier. Or more than one amplifier, depending on the number of speakers you want. Since DTS-HD MA I can't tell any difference anymore between it and newer stuff. So for me that's the end of that ladder. Also important: Fix the room. I.e. minimize reflections. Correct speaker position. Correct seating, if this is for a home theater.

At my main PC workplace I use for the audio chain two wall-mounted easy to drive Monitor Audio Bronze 2, an Amptastic Mini-1 amplifier with a genuine Tripath TA2020, and an E1DA 9038D USB sound dongle. Fantastic transparency (which I like - some find it tiring) and very good low end on tracks like Spandau Ballet's "Gold". Dumped all MP3s years ago, now using either FLAC, or nothing.

 

[Fritz]

This Yammy is by far the best sounding AVR I've ever owned, hence my attempt to repair it. A lot of people will argue that all AVR's sound the same, I always assumed this was true until I got this Yammy. It's the cleanest sounding punchiest AVR I've ever owned. My previous AVR, a Denon, sounded mushy and no matter how much I adjusted, ran Audussey, etc, I barely got anything out of the sub. Not so with this Yammy, If necessay I'll buy another but this one suits me just fine as long as it works.

And BTW, the problem is it has to warm up for 15 to 20 minutes before any sound comes out. Also, if I turn on the ceiling fan right above it the sound will cut in and out. I can put a folded up towel over the area where the chip is and it will no longer cut out. This is a well know problem.

 

[Stephan]

So they produced an AVR that isn't lame by accident, got it. ;-)

Did you watch

?

Aluminum foil is ok, but Kapton tape would be better. Also should be attached much closer to protect other components from heat. Other than that, technique is ok.

 

[CyklonDX]

https://www.youtube.com/@northwestrepair

here's few quite good videos showing soldering expert (he's also taking repair jobs - and isn't expensive as he isn't certified -- he charges around 100 bucks per gpu job -- he's taking SSD's and other stuff so vcr or something shouldn't be an issue)

 

[piranha32]

I disagree on the trickyness, or rather, i guess it depends on the sizes of the pads on the PCB and IC.
the further away they are from the pins on the edges the less of an issue.

It's not tricky if you know what you're doing. I agree that a big thermal pad is easier to deal with than pads in e.g. dual row QFN, but for someone with no experience it can be an unsolvable mystery how the hell they solder this weird pin with no access to it. Been there, done that.

 

[Fritz]

So they produced an AVR that isn't lame by accident, got it. ;-)

Did you watch

?

Aluminum foil is ok, but Kapton tape would be better. Also should be attached much closer to protect other components from heat. Other than that, technique is ok.

Mind is the same. Even passed the heat test. At first I thought it might be a cold soldier joint that made contact after it heated up but alas, this is not the case, the chip is bad.

 

[Wasmachineman_NL]

Speaking of soldering, I successfully repaired a Dell Inspiron 1150 it's DC jack today! Boy what a shoddy job that previous guy did. Damaged the chassis of the laptop in question in multiple places and didn't even fix it.

 

[RageBone]

850 degrees, does that sound right?

That does not sound right to me.
What are you using for soldering? A Hot-Air station or a Heat-Gun?
I was talking °C do you mean °F ?

To maybe explain the dangers a bit more, PCBs are not meant to get hot for long and their specific ratings depends on the materials.
So in general, the hotter and longer you point at the pcb, the more you will tax its materials.
In the absolute worst case, the glue holding the layers together softens and expands separating the PCB layers from each other.
We call that "popcorning" and it leaves a visible indent-able bubble where it happened.

To be absolutely clear, the thing is dead after that happened.

Likelihood of it popcorning goes up with Time and Heat.

There luckily is usually some tolerance and room for error.
In general, if the solder isn't melting yet, then the board hasn't actually hit the temperature where the solder melts.
That usually is because the more layers a PCB has, the more material and especially copper there is to transport heat away from where you want it to go.

Solutions are of course to soak the board first, i heard some use an oven for that, i was recommended to just keep the hot-air at 150 or 200°C and keep it at the board for a while, those temperatures being on the low end of risks or anything happening.
A Pre-heater would also solve those issues.

 

[Fritz]

I believe it displays Fahrenheit. It didn't come with a manual and I couldn't find one on line but I did find a reference to the temp range in Celsius. The max is 450c so 850 has to be f.

If this is the case I can tell you that with it displaying 392 it's not going to melt solder.

 

[Wasmachineman_NL]

Speaking of soldering, I successfully repaired a Dell Inspiron 1150 it's DC jack today! Boy what a shoddy job that previous guy did. Damaged the chassis of the laptop in question in multiple places and didn't even fix it.

Celebrated too early, DC jack broke again :|

**** it, up for parts it goes. Can't be arsed to disassemble it again and my iron is a piece of shit anyway.

 

[RageBone]

I believe it displays Fahrenheit. It didn't come with a manual and I couldn't find one on line but I did find a reference to the temp range in Celsius. The max is 450c so 850 has to be f.

If this is the case I can tell you that with it displaying 392 it's not going to melt solder.

Right, i am a °C guy, so i can't help you with it in °F

 

[Fritz]

Right, i am a °C guy, so i can't help you with it in °F

Google can translate f to c and vice versa.