Specification of a thermal camera for PCB repairs - some thoughts

[Fraser]

Hazel,

It all depends upon the nature of the PCB analysis and detail required. Commercial thermal analysis of an RF amplifier module that is built on a ceramic substrate with bare dies and bond wires visible may require very high camera resolution to thermally profile the components on the module. With commercial thermal imaging of PCB’s there is greater justification in using higher resolution thermal imaging equipment as R&D work is often pushing the boundaries of technology and some level of “future proofing” is advisable. Hence why I said that a commercial user should buy the best that they can justify and afford. Unlike a hobby user, commercial users can gain financial benefit from the use of an advanced thermal imaging system and so the equipment pays for itself over time. I own a FLIR SC4000 cooled thermal camera that cost its original owner £150K. It was bought for R&D work that involved imaging the hot target through glass and ceramic panels. They could justify the investment because no other technology could obtain the data they required for the R&D work. Mistakes at the product development stage would cost the company Millions of Pounds if the product failed in service or was subject to a recall. The commercial world of thermal imaging is highly complex and a thermal camera manufacturer will often send a sales person to the site to discuss the options available and guide the customer in their decision making process. The sale is likely to also include lens options and these re selected to suit the required task. Such can be very expensive in themselves as some commercial customers require magnification to create a thermal microscope capability. A lot of money can be involved so the visit is justified for both the camera supplier and the customer.

I attach some pictures of some bare die and miniature electronics PCB’s that would challenge non specialist thermal imaging systems when it comes to assessing individual components thermal profile. This is an extreme case of course and many commercial users will have less demanding thermal targets. That is why the needs of the customer need to be discussed and recommendations made on what resolution and other characteristics will best meet their needs.
Fraser

[Fraser]

To demonstrate that even a low resolution thermal imaging system has very real uses I have just purchased a faulty multimeter that contains an 80x80 thermal imaging core with a nice narrow FOV 21x21 degrees lens. The microbolometer pixel size is a relatively large 34um  . I believe the core to be a Lynred (was ULIS) Micro80 microbolometer module. This module is ground breaking in that it is a BGA design intended for mass production of equipment that does not require a high resolution thermal image. As I have stated in the above text, 80x60 pixels is adequate for non demanding tasks. 80x80 is a 1:1 aspect ratio version of the old 80x60 sensor array as it is intended for applications that include machine vision and Industrial scene observation where a 1:1 aspect ratio is advantageous. The multimeter is intended for general use but contains many Bluetooth linked logging features that appealed to me and it is capable of acceptable thermal imaging of larger targets. It would not, however, be my first choice for PCB repair work. If I fit a close-up lens to it then it may actually have uses for smaller thermal targets. We shall see. First I shall have to see whether I can repair it !

The unit is branded Voltcraft but it is made by CEM. It is normally very expensive !

Review…. https://youtu.be/uoeS0dV4SzU?si=by0T9cJTsHVCiGJt

Why did I not buy a working Mustool MT13s that claims 192x192 pixel resolution ? Whilst the Mustool MT13s is also a multimeter plus thermal imaging camera, it is best described as a compromise solution. It is built down to a price, so corners have been cut in its design. I also remain unconvinced about its resolution claims.

Fraser

[Hazel]

Hello Fraser,

Thanks a lot for your kindly reply.
Actually, I am a machine vision sales, but my profession is not related to this.
So I think I still have a lot to learn, and the knowledge about PCB looks really very deep for me.
 Thanks for your patient reply, I think when dealing with a customer, it is also more important to understand what he actually needs before making a recommendation.

Best regards,
Hazel

[Fraser]

Hazel,

Yes, advising a customer on which thermal camera they need, based on their particular requirements, can be quite a challenge. The relatively low resolution of thermal imaging cameras compared to visible light cameras makes it more important to get the right IFOV and this dictates choice of sensor array resolution, lens choice and working distance. Basically, you need enough pixels being illuminated by the target of interest to meet the needs of the customer. If we use the humble SMD resistor as an example case….. it is recommended that at least 4 pixels are illuminated by the resistor. The sizes or resistor vary but modern electronics tend to use very small parts such as 0402 and 0201. With a IFOV that permits 4 pixels to be illuminated by the SMD resistor, the user can measure the temperature of that component but no real surface detail is present. To see the thermal profile of the resistors surface, many more pixels are required. An SMD resistor commonly has a tiny hot spot at the centre of it, where the actual resistance is set. The heat from that central spot then migrates outwards across the ceramic substrate until the heat is sunk into the solder pads at each end. I have no definitive answer to how. Many pixels are required to image the SMD resistor well enough to see the central hot spot but a minimum would be something like 9 pixels which would localise the position of the hot spot and show the migration of heat away from it. For greater detail I would recommend at least the times that number of pixels covering the resistors surface.

Some questions for the customer that come to mind…….

1. What is the nature of the thermal target that needs to be imaged ?
2. What is the dimension of the smallest thermal target that will be imaged ?
3. What level of detail is required for the smallest expected thermal target ? Temperature measurement or surface details ?
4. What is the expected working distance of the camera from the thermal target and are there options to reduce this if required ?
5. What is the expected temperature of the thermal target ?
6. What is the expected temperature differential of the target compared to its background (approximately) ?
7. What is the average ambient temperature of the area in which the imaging of the thermal target will take place ?
8. What level of measurement accuracy is needed ? Customer should be advised of nominal +/-2C or +/-2% tolerance in the Industry.


There are many more questions that need to be asked to match the customer to their “ideal” thermal imaging system but these are the basics. From the answers it would be possible to determine the required sensor array/lens combination for the required IFOV and the thermal sensitivity requirement of the system. These are the starting points that could make the difference between a reasonably priced  320x240 or 640x480 pixel imaging system and a very expensive Higher resolution solution. A very high resolution sensor array can find its resolution squandered by the unnecessary use of a wide angle lens block. In some cases, the customers needs justify the purchase of a mid range camera resolution that has a removable lens so that different lenses may be attached for different use scenarios or thermal target sizes. Changing lenses may be practical in some cases and not others however.

In the case of selling thermal imaging systems to a customer, it is helpful if the customer has a good understanding of thermal imaging systems and knows what they need. The “intelligent customer” is what they tend to be called. They will effectively tell you what they need to meet their requirements and you just need to check their thought processes to make sure they have not made an error in their thinking. When a novice user of thermal imaging systems asks you to provide the complete solution to their needs when they are unsure of those needs, life can become more challenging as you need to educate the customer regarding why you are recommending a camera system of certain specification. A novice user may be quick to complain if they cannot make a recommended system perform as they wish, no matter how unrealistic their expectations may be ! This is why large thermal imaging manufacturers, like FLIR, employ Industrial market sales staff who are trained in thermography.

Fraser

[Fraser]

My review and testing of the Dianyang Technology CA10 PCB thermal Analyzer may be of interest….

https://www.eevblog.com/forum/thermal-imaging/review-dianyang-technology-ca10-circuit-board-thermal-analyzer-repair-rd/

It contains test on various SMD resistors where you can clearly see the hot spot at the centre of the resistors top surface. The CA10 has a fixed FOV lens but manual focus so the distance between the camera and the SMD resistor could be changed to provide the largest image of it. This is not a thermal microscope though.

I attach the SMD resistor tests here to illustrate my comments in the previous post.

ThecCA10 cameras optical resolutions is 256x192 pixels but the images are upscaled to 640x480 in the attached sample pictures.

Fraser

[Fraser]

My Infiray P2 Pro review may also be of interest as it contains a test demonstrating the effect of the distance between the camera and target on target detail as a result of IFOV.

https://www.eevblog.com/forum/thermal-imaging/review-infiray-p2-pro-thermal-camera-dongle-for-android-mobile-phones/msg4575070/#msg4575070

Fraser

[Fraser]

Hazel,

I do offer consultancy services if you need someone with the required thermography knowledge to match a customers requirements with a suitable thermal imaging system.

Fraser

[MrSheep]

Fraser,

Have you used your SC4000 to image circuits yet ? I have been using my MWIR cameras for circuit analysis on and off. Just haven't had the time to post about it haha.

[Fraser]

No sadly my SC4000 cooled camera is tucked up safely in its hard case as I have not had the time to use it for anything recently. There was a microscope lens for these cameras and that would be great fun to use 

I do feel a little guilty owning such a camera and not using it, but I am very attached to this lovely high speed cooled camera so have not looked at selling the unit.

Fraser

[MrSheep]

yeah I feel the same way haha. Don't think I would ever sell mine either. Even the amber ones. They are museum pieces to me.

I finally got some 3-Tab/4-Tab bayonet adapters for my SC cameras. I can use my 4X lens properly now. Will post about it sometime in the future.

[Fraser]

I have some AGA 780 series MWIR lenses that use a threaded mount. I need to design a suitable adapter so that they may be mounted on the SC4000 and Amber cameras. Glad you got the adapters you needed  These cooled cameras would produce very nice, low noise, images of PCB components. As I said, there was/is a proper thermal microscope lens available for them. Crazy expensive no doubt !

[Hazel]

Hello Fraser,

Thank you for your very patient and helpful reply.
In fact. I have a lot more to learn.
In addition to facing the need for IR products for electronics repair, there are very many applications that require the use of IR cameras.

Thank you very much for your help, I'll write to you if I don't understand anything.

Best regards,
Hazel

[Phil1977]

I can attribute some real life pics...

A supercap bundle with bleeding resistors in it´s "normal" state


Two bleeding resistor supplied with around 3W to create some heat:


Thermal image with the ToolTop ET692C:


The same with overlay mode - with the smallest distance where both images can overlap:


The ET692C with a f=150mm ZnSe laser window as a close up lens:


The Infiray P2 Pro without lens


The Infiray P2 Pro with the 150mm ZnSe lens:


The 3D-printed lens holder for the Infiray


Some words about both devices:
The performance of the Infiray is much better than the Tooltop though both units have the same nominal resolution. I anyhow mostly use the Tooltop first because it´s just "ready-to-use" at the bench and the pistol-grip form factor is really quite convenient to use. If I need pictures or especially videos for documentation, I take the Infiray or borrow something professional.

Both cams are great utilities - especially regarding their low price. It´s the same with all kinds of cameras: The best camera is the one you have with you!

And one remark regarding Frasers great knowledge summary: If you want to define specifications, I think you have to clearly decide if you want a thermal imager for failure detection or for temperature measurement. From my personal experience most of the cams - even like the two cheap ones I used for the samples - are well suited for seeing temperature differences and detecting failure points. The most important qualities for this seem to be temperature resolution (MRTD), image resolution and frame rate. Temperature accuracy is not very important for that purpose.
Things change quite a lot if you need to measure absolute temperatures. Sometimes you need much more calibration than choosing an emission factor only. You also have great benefit from a cam with a really low SNR - and there not only the stochastic noise of the camera is important, but also the resilience of the cam to stray radiation, internal emission and other slowly changing deviations. Professional cameras with high quality and high aperture lenses together with a software that allows good calibration runs can help there a lot.

[Fraser]

Just as a warning regarding resolution specifications….

The Voltcraft WBM-460 that I have purchased as a repair project has specifications that, I believe, are intended to deceive

The resolution is stated as 120x120 microbolometer pixels and this is repeated in the text of the user manual that claims 120x120 temperature measurement points are present. Any reader would understandably think this camera has a 120x120 pixel thermal imaging core in it. This is not the case, however. From the specifications given I believed the unit contained an 80x80 pixel Lynred Micro80 imaging core (The 34um pixel size is unusual For modern budget microbolometers).Everything but the resolution matched. Lynred do not make a 120x120 pixel version of the Micro core.

Further investigation found the same thermal multimeter under different brands names. Most repeated the 120x120 pixel misleading specification. One had both 120x120 pixels and 80x80 pixels as the resolution in the same document ! Further research discovered a very similar thermal multimeter branded “Metrel” (a UK company) that was actually honest about the true resolution of their 9880 thermal multimeter product. Not only did they state that it contains a 80x80 pixel microbolometer, but they dedicated a page of the user manual to explaining resolution, microbolometer pixel size, FOV and IFOV ! A most excellent inclusion in the manual. As expected, all the specifications surrounding the Metrel thermal imaging core matched those of the WBM-460 (lens choice, Pixel size, FOV and IFOV). The IFOV calculations in the Metrel manual proved that the microbolometer in the WBM-460 has to be am 80x80 pixel resolution die.

I am disappointed that manufacturers continue to inflate their products specifications and it can be challenging to determine the truth behind those fictitious claims ! These thermal multimeters are not sold at bargain prices and cost around £700 yet the deception is present. Kudos to Metrel for standing out from the crowd in this case and being honest about their product 

WBM-460 manual

https://asset.conrad.com/media10/add/160267/c1/-/gl/001661486ML01/manual-1661486-voltcraft-wbm-460-ir-cameramultimeter-combo-20-up-to-260-c-120-x-120-pixel-50-hz.pdf

Metrel similar thermal multimeter with the same imaging core specifications except stated resolution:

https://www.es.co.th/Documents/MD-9880MUNUAL.PDF

In some of the misleading thermal multimeter manuals that I read it was interesting to see the ‘manufacturer’ claim a 120x120 pixel microbolometer resolution, yet also state that saved thermal images were only 80x80 pixels 

Update: Captures of Voltcraft and Metrel specifications added, along with the Metrel page on IFOV.

[elianto]

Real PCB from HIKMICRO Mini2Plus V2,
256 × 192, manual focus, FOV 25° × 18.8° , focal lenght 6.9 mm, SuperIR active

[elianto]

Real PCB from FLIR ONE PRO,
160 × 120, fixed focus (image are out of spec., min. focus distance 15 cm), FOV 55° × 43° , MSX not active (minimum distance for MSX 30cm)

[DaneLaw]

Two very old examples of a laptop motherboard.
Xiaomi MI Air13 2016/2017
320x240 Seek Pro FF (2017)


Running Geekbench4 benchmark.. its a Skylake CPU with a 940MX GPU.
Loved how I could see the radiating all the way out to the screws, when loaded hard.

* IR lens used on the above picture as the manual focus doesn't do macro.

[Fraser]

The Voltcraft WBM-460 Thermal Multimeter arrived from Germany today.

Upon opening the case I found exactly what was shown in the auction. The battery charger “shoe”, test leads, and thermocouple are missing but easily replaced. The Multimeter had its battery charged and fitted so I switched it on. It works perfectly in all respects so no repair is required. I like that that both the thermal image and the selected multimeter function are both displayed together as that can be useful when wishing to monitor/capture a thermal image whilst also showing a voltage or current measurement related to the test. I shall take some images of a PCB and upload them here to show what can be achieved with a 80x80 pixel Lynred Micro80 microbolometer.  It produces nice pictures of my coffee mug !

Fraser

[djsb]

Is there a UK importer for the Dianyang Technology PCBA tools? Or can they be purchased directly from China? If so, which one would you recommend, and what is the ballpark cost? Thanks







PS My sole use is for fine detailed PCBA fault diagnosis down to SMT level.

[Fraser]

From my last conversation with Dianyang technology, it appeared that they were moving into a “OEM for other brands” mode of operation. They have faced challenges getting the DYT brand well known in the World marketplace so make thermal imaging solutions for other companies who already have a good market presence and reputation. Many of the PCBA inspection thermal cameras that you see coming out of China are, in fact, made by DYT. Qianli products being a good example. You will find many PCBA analysis thermal cameras on the market that look the same…. They are, in fact, basically the same product. DYT tend to use the 256x192 pixel Infiray thermal imaging cores. These provide decent imaging of PCBA’s at reasonable cost. The software supplied with PCBA thermal analysis cameras will often differ between brands and price point. More capable software comes with units that carry a higher price tag. A case of ‘standard’ and ‘Pro’ analysis software options. For many repair techs, the standard software is more than capable of meeting their daily needs. The Pro versions of the analysis software is aimed at R&D environments where more advanced measurement options are desired.

I have no connection with DianYang technology,  beyond having reviewed their CA10 PCBA analysis camera, but I believe the DYT products to be a very capable and well made solution for every day PCBA thermal analysis. I also own the FLIR ETS320 and I prefer my CA10 even though the resolution is a little lower. For more demanding analysis tasks, DYT make higher resolution products but at higher cost.

If you search for “PCB thermal analyser” with Google, you should find several different models of unit, but you may notice a similarity in any example images and the gun metal grey colour of the camera system (which I like!) Those grey coloured systems are likely all from DYT. Take a look at the thermal imaging products from Qianli to see what DYT have made for them. Compare those products with others available at lower cost on the internet and you will find the same units under a different brand. With regard to UK suppliers…. You may find UK mobile phone repair product suppliers selling these camera systems, but most buyers import them from China to save on cost.

Fraser

[Fraser]

Some example PCBA thermal analysis cameras from a quick Google search. NOTE, I am not saying that all of these are from DYT, but most are and Qianli use DYT camera systems with their own analysis software solution. The older products can use 160x120 pixel cores or SEEK Thermal cores and these are best avoided. The specifications will show which core is in use. Look for 256x192 pixels or sometimes shown as 260x200 ! (Marketing team getting carried away!)

Fraser