Possible to make a pcb smaller (shave off edges)? - Page 1
Forum section: electronics / beginners

author: idoit
author_rank: Contributor
timestamp: December 30, 2021, 04:55:29 pm
content: Hi everyone,I have to fit 2 PCBs in a tight spot, so I need to shave as much from them as possible, so long as they don't get damaged. They are the fingerprint reader (the small square one) and LED module (the long one) boards from a X230T. I tried to attach a couple of photos from each of them here but I could only upload two. Please look at all 10 images here on imgur:https://imgur.com/gallery/H5odRMGFirst 6 images are for LED board and the other 4 are fingerprint reader.For the LED board, can I shave off the lower bottom edge a bit? Based on the images, are there any traces there? There are a few spots that I need to make a dent and I have marked them as small red rectangles. I have put them underneath the area of interest, so it doesn't block the view. Can I make a small cut in these areas or are there traces there? What are those tiny dots?For the fingerprint reader, I have show a red line I am interested to cut along. I also need to shave off a bit from right or left side (even 1 millimeter or less counts) Can I do that without damage?In general, how important are the ground spots (where screws go in the hole)? For instance, there are 3 grounds in the fingerprint board. Can I just ground 1 of them? (since they is continuity between them three)I know I asked a lot of questions! I appreciate any input. Thank you so much

author: idoit
author_rank: Contributor
timestamp: December 31, 2021, 12:14:29 am
content: Would it be possible to clone the LED board on a smaller PCB?

author: gnuarm
author_rank: Super Contributor
timestamp: December 31, 2021, 03:52:35 am
content: It looks like the cut on the fingerprint reader could be done as long as you don't get too close to those two vias you show under your very broad line. I can't tell how large your board is but 1 mm on each side might be ok. You have the boards, you can take measurements. Can't you tell us how much room you have to the important copper bits?On the finger print board are there any inner layers? What does the back side look like?

author: idoit
author_rank: Contributor
timestamp: January 01, 2022, 05:08:09 pm
content: Quote from: gnuarm on December 31, 2021, 03:52:35 amHi, thanks for your reply. Like I said, I couldn't upload all the images in this thread, but here they are:https://imgur.com/gallery/H5odRMGQuote from: gnuarm on December 31, 2021, 03:52:35 amWould you be able to mark the edge up to where it's safe for me to cut? Both on the right and left edges and top part. Thank you.

author: Simon
author_rank: Unknown
timestamp: January 01, 2022, 05:13:21 pm
content: If you check the notes on the upload you will see the limits. You files are rather large and bigger than necessary to view on a screen so if you resize and recompress you will likely save a lot of file size.

author: gnuarm
author_rank: Super Contributor
timestamp: January 01, 2022, 05:44:36 pm
content: I don't understand what you are trying to do with the long board. Here is a markup of what you might get away with on the fingerprint board.The top edge is limited by the two vias by the markings C22 and C11. Don't get too close to them. The right side can be cut some, but the left side has surface mount components very close by so there's very little material you can remove. If you do don't use a saw. Use a belt sander and hold the board along the line of the belt. You want to avoid applying a bending stress to the board as it can damage the components next to the edge.There's another fly in the ointment. If you look at the two vias on the top of the board you will see on the "front" photo they dont't connect to anything. So they must be connected in an inner layer. You have no way of knowing if you are cutting off that connection since you can't see it. I could guess about this connection, but it would only be a guess. So good luck.

author: idoit
author_rank: Contributor
timestamp: January 02, 2022, 03:21:59 am
content: Quote from: gnuarm on January 01, 2022, 05:44:36 pmI am just trying to fit it in a very tight spot. If you can do the similar thing that you showed with fingerprint reader with red lines, that would be awesome (on top and bottom edges).Quote from: gnuarm on January 01, 2022, 05:44:36 pmThank you very much. This was very helpfulQuote from: gnuarm on January 01, 2022, 05:44:36 pmI made some cuts. I will report back if I damage anything in the mid-layer@Simon: Thank you. Yes, I did but as I didn't have a software readily available for jpg compression, I took the easiest path. I know I could have used some online websites for image size reduction, oh well next time

author: ledtester
author_rank: Super Contributor
timestamp: January 02, 2022, 04:14:07 am
content: Quote from: idoit on January 02, 2022, 03:21:59 amI just take screen captures of the images and that produces reasonable sized files. Use your OS's built-in screen snipping tool. Doing so also removes EXIF data from your camera images -- like GPS coordinates.

author: gnuarm
author_rank: Super Contributor
timestamp: January 02, 2022, 04:33:13 am
content: Quote from: idoit on January 02, 2022, 03:21:59 amI reduced the size of the file I posted by reducing the number of bits in the image using MS Paint comes with Windows. It's very easy to use and is quite useful for simple tasks like drawing simple lines or adding a bit of text. You can also scale images up or down or even change the file type.

author: Simon
author_rank: Unknown
timestamp: January 02, 2022, 10:03:07 am
content: An image width of 1000px is plenty for online forum use unless it makes sense that we download the image and then zoom into it. It can only be as large as the width of the forum post, sure I have a 4k screen, but I have a 4k screen so that I don't see the pixels, so even then 1000 pixels wide is enough to convey the, uh, picture.I do web hosting and one organization who I host who I am also a committee member for kept running out of space. They were willing to give me more money for more space but I said this would not help as the reason was that they were uploading photos from phones for blog posts and people were sending in report emails with photos so it was just ballooning. If I gave them more space they would just fill it in weeks. The answer was to simply delete all the old emails that were no longer needed with their 20MB attachment size from just 3 photos and to delete all the original camera photos uploaded into wordpress as these were being resaved as smaller versions by wordpress when they made the blog post. Suddenly they had all their space back. Phone photos have low compression to save battery power. Also remember that the pixel count goes up or down by the square of the change in length of one side so halving the width will take 1/4 the space, quite the saving before you even worry about compression ratio.

author: Gyro
author_rank: Super Contributor
timestamp: January 02, 2022, 10:41:26 am
content: 'Resize', by Peter Bone, is a great application for downsizing JPGs with very little loss of detail. It's a small (<1MB) standalone exe which hasn't changed since 2005, it just creates a .ini file in the same folder to store preferences. It supports batch file resizing, drag and drop etc. and still works on current windows versions. It drops the resized version back in the target folder with a Resized_ prefix. Recommended.https://resize.en.uptodown.com/windows

author: Ian.M
author_rank: Super Contributor
timestamp: January 02, 2022, 11:48:44 am
content: My preferred 'Swiss army knife' tool for image processing and minor editing for web use isIrfanViewIts free for individual noncommercial use. I regularly use it to crop and resize JPEGs for web use as one of its JPEG save options is to set a file size limit. I also use it when working with schematics and other line art to auto-crop borders then add back a small border, and to reduce the color depth, usually to 16 colors, for better lossless compression. It also supports multi-file batch operations, and command line operation, but I seldom use those nowadays as I am no longer responsible for wrangling the images from a club photo competition (which involved processing hundreds of full resolution photo files to web-friendly resolutions and scripted generation of a powerpoint presentation of the winners and slideshow of the rest for the prizegiving).

author: AnasMalas
author_rank: Regular Contributor
timestamp: January 02, 2022, 06:28:00 pm
content: Quote from: idoit on January 02, 2022, 03:21:59 amStop! before plugging the boards in, there is a critical step: You need to sand the edges with very fine grit sandpaper (start with something like 200 and go all the way to 1000-2000), until you are sure there is no dangling copper (try to look at it with a magnifying glass). Otherwise you could have a shorted line or plane.Quote from: Ian.M on January 02, 2022, 11:48:44 amGod! that is an absolute blast from the past! I remember trying to run it on my first gen core i3, it did not like it!

author: Ian.M
author_rank: Super Contributor
timestamp: January 02, 2022, 06:36:26 pm
content: Quote from: AnasMalas on January 02, 2022, 06:28:00 pmI've been running it in one form or another since the late 90's. I *think* the first machine I ran it on was a Win98SE Dell Pentium II box.

author: AnasMalas
author_rank: Regular Contributor
timestamp: January 02, 2022, 08:20:15 pm
content: QuoteHaha it was the laptop that struggled with... existing. I remember wanting to edit a fast paced cut "with the beat" type of video, and the laptop was so slow that the *only* way to do it was to make the cuts according to the time stamp, wait 5 hours for it to render the 40 second clip, then go back and change the time

author: idoit
author_rank: Contributor
timestamp: January 02, 2022, 09:10:28 pm
content: Thanks for all the supportI should have mentioned I use Linux, but I can just usewineor have it on Windows XP/7 VM.The longer LED board is 6.5 inch (aka 17cm). Ideally I would have liked to be able to clone it to a smaller pcb (look in the attached image for instance), but I am not sure how to go about that. Is that even possible? Is having schematic necessary? Where to obtain it? (like I mentioned, it's the LED board from ThinkPad X230T tablet)Quote from: AnasMalas on January 02, 2022, 06:28:00 pmCan you elaborate what your concern is? Is it to avoid shorting circuits, if the edges of it touches another metal? Sorry I am an electronoob.

author: amyk
author_rank: Super Contributor
timestamp: January 02, 2022, 10:24:56 pm
content: An x-ray of the board will definitively tell you whether there are traces in that area. You may be able to get your dentist to give you one.

author: gnuarm
author_rank: Super Contributor
timestamp: January 03, 2022, 01:00:43 am
content: The concern of Anas is that if you remove just enough copper that there is only a tiny sliver of copper left along the edge, it could come partially dislodged and be bent over without even being seen. It could short to other layers or even be bent over the board shorting to circuits on the board.