I’m not one to usually assume things, but I have seen this way too many times and it’s usually caused by the person who completed this repair. Most cases are the person installed a really cheap aftermarket screen and those usually tend to have issues with contrast and saturation. This person also may have skipped this important step when repairing this specific phone found here: https://www.youtube.com/watch?v=xMeAnY_j... Programming the screen is needed for the light sensor and true tone functionality to work and so many people/repair businesses fail to do so. Do you see any text that says “True Tone” found in settings < display and brightness?
Have you tried to test signs of life like toggling the mute switch on/off? If the battery is not dead but the LCD won’t display anything, that doesn’t always mean that the iPad isn’t on. If you plug the iPad in for awhile (rule out dead battery) and if the vibrating motor on the mute switch still works, then toggle the mute switch on/off and you will be able to feel that vibration. If you want to diagnose even further, you can always open the iPad, unplug the LCD from its connector on the logic board, then proceed to use multimeter and measure that connector on the logic board. I personally do not know where to obtain the normal values measured from that connector other than a shematic, measuring the same but working iPad, or someone on here that has access to schematics and values and knows which points to measure.
It’s entirely up to you and also depends on the size of the IC. If you feel that taping an IC to a stencil is what makes you feel comfortable and holds the IC in place, that’s definitely ok. I personally use Kapton tape (heat resistant tape) . I have done both ways a few times and after you get a hang of it, you just kind of become used to it. It is ideal to tape really small chips that have a decent sized ball grid array to the stencil.
I personally like metal stencils. It offers the advantage of using solder paste which can then be spread on the stencil like butter on bread. Then the solder paste can be transferred to the ball grid array with heat while the stencil is still on top of whatever you are soldering too. It has an advantage over non metal because you don't need to find the proper size of solder balls to manually load each ball 1 by 1 onto your stencil to then transfer to your grid array. You also don't need sticky flux to keep the solder balls in place after lifting up the stencil. In the end metal stencils are less tedious and less prone to error. Metal stencil use example: https://www.youtube.com/watch?v=3_DsWcg0... (1) skip to 5:48 As for non metal, it’s hard to find an example because it’s an old and inefficient way of completing a re-ball task. The flow goes as follows: (1) Make sure chip is cleaned and ready to receive solder. (2) Apply sticky flux to the ball grid array on the chip. (3) Put non metal stencil over sticky...
Honestly you really don't need to worry if it was just a few drops on the keyboard. If you are really worried, you can take the keys off the keyboard, get some q tips, 99% isopropyl alcohol and canned air, then just clean in between the keys with alcohol on the q tip and canned air to quickly dry/evaporate the alcohol. But to me you should be fine if you leave it as is.
With the current situation that the world is in with the coronavirus, this can differ for everybody, but the best way is to hand it over to businesses that have access to properly recycle batteries. Put some kind of tape over the contacts of the battery, then you will want to either take it to a local recycling center (places like this usually do take batteries but call to make sure) or you can try a tech repair store like batteries + plus and bulbs and they will take your batteries for recycling. Thanks for being friendly to the environment :)
Regular packing tape has never really worked for me. If a screen was really destroyed, I would use duct tape which worked well, but I would leave the edges (path of the heat gun) of the digitizer not taped. Doing that limited the amount of heat on the tape reducing the chance of a burning tape odor. I would then just manually remove what remained on the frame of the iPad. I wouldn’t recommend UV glue because it’s expensive and risky in that matter.
If you ordered the correct screen type, that is a wholesaler issue. Did you put both screens side by side and examine both connectors? Are there any bent leads on the new screen’s home button connector? Where did you order your part from?