Opening a TO-3 without damaging it - Page 1
Forum section: electronics / projects

author: Stonent
author_rank: Super Contributor
timestamp: November 11, 2013, 10:29:17 am
content: I've got a few ST brand 2N3055 transistors that I bought for the sole purpose of opening up and using them for experiments in cheap radiation detection.I'd like to de-cap them with as little damage as possible. I could probably borrow a dremel but I don't want to fling sparks and bits of metal inside during the cut. (I live in an apartment so I don't have a vise or a lot of tools here with me)I don't suppose they just solder the cap on and I could just remove it with enough heat?I found this picture of one opened and it looks like the cap is just bonded somehow to the outside.http://obrazki.elektroda.net/68_1240402529.jpgIdeally to do this right, I'm going to need to block light out from the transistor as outside light can trigger it. Since Mica is used in Alpha particle probes to physically protect the inside of the Geiger tube but not block Alpha particles, I had an idea of using Mica that has been coated with a thin layer of ink from a marker to block the light but let Alpha radiation through.Yep. Another one of my projects.

author: amyk
author_rank: Super Contributor
timestamp: November 11, 2013, 11:43:20 am
content: You mean without damaging what's inside? The way you wrote it looks like you want to somehow have the cap snap back on like before...As long as you don't cut too deep it should be OK; just carefully clean the insides once you're done.

author: tsmith35
author_rank: Frequent Contributor
timestamp: November 11, 2013, 11:51:37 am
content: I remember a YouTube video where a guy used acid and heat to remove the packaging from some chips. Didn't seem to affect anything inside, but acid could be messy to work with...

author: ciccio
author_rank: Frequent Contributor
timestamp: November 11, 2013, 11:52:51 am
content: I once had to open a lot of TO3 cases to investigate a reliability issue.The simplest way to open them, apart using a Dremel, is using a fine metal saw and gently cut around the cylinder's base.Some cases are built with very thin sheet metal, other use more hard to cut material.But without a vise I see the thing very hard...

author: Stonent
author_rank: Super Contributor
timestamp: November 11, 2013, 12:03:29 pm
content: Quote from: amyk on November 11, 2013, 11:43:20 amI do plan to re-seal it in some way, not necessarily with the original cap.I suppose it would be nice to get the cap off, then fully drill it out and seal the mica inside it some way and superglue it all back together.

author: Fraser
author_rank: Super Contributor
timestamp: November 11, 2013, 12:25:27 pm
content: I have de-capped 2n3055's by placing the cap part in a vice, crushing it slightly, rotating the cap, crushing again and so forth. It cracks the weld around the caps base. No sparks, no heat, little risk to the die that is in the middle on a raised platform.

author: c4757p
author_rank: Super Contributor
timestamp: November 11, 2013, 12:26:01 pm
content: I've some Russian germanium transistors that are weak enough to decap with wire snips. Want me to mail you a few? Even just to play around with a different semiconductor in this application.

author: flolic
author_rank: Frequent Contributor
timestamp: November 11, 2013, 12:36:47 pm
content: Quote from: Aurora on November 11, 2013, 12:25:27 pmThat's exactly how I did it

author: dr_p
author_rank: Frequent Contributor
timestamp: November 11, 2013, 01:29:40 pm
content: I have a 7812 and a 7805 in TO3, both TESLA branded, and didn't really know what to do with them. I guess now I doI'm curious to see if they work with the lid off.

author: Stonent
author_rank: Super Contributor
timestamp: November 11, 2013, 01:34:05 pm
content: Quote from: c4757p on November 11, 2013, 12:26:01 pmI think that might be interesting to try. I'll even do a video on it.

author: c4757p
author_rank: Super Contributor
timestamp: November 11, 2013, 01:35:19 pm
content: PM me your address and I'll get them out today or tomorrow.

author: Rufus
author_rank: Super Contributor
timestamp: November 11, 2013, 03:15:16 pm
content: Quote from: Stonent on November 11, 2013, 10:29:17 amMostly they are resistance welded with a single pulse. Years ago I used to look after machines that did it.They used to check them by putting a 6" spanner about 1 foot away from the contact, if the spanner jumped in the air and hit the contact they knew they were getting good welding current.

author: G7PSK
author_rank: Super Contributor
timestamp: November 11, 2013, 03:38:47 pm
content: I have a lot of glass encapsulated germanium transistors (OC 70-71 equivalents) made by Newmarket transistors in the 60' and 70's they used to be used for radiation detectors and light detectors back in those days I can send you some of those, I was wondering what to do with them just the other day, it seems a pity to just throw them out.

author: Legit-Design
author_rank: Frequent Contributor
timestamp: November 11, 2013, 08:53:21 pm
content: I would start with a hacksaw, like in that video, with the method he described. Use compressed air to blow away all the metal dust.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 12, 2013, 03:22:52 am
content: Hi,My method to de-cap TO-3 transistors, is to hold them in a vice by the pins and file around the top of the can at a 45 degree angle. This leaves a nice sharp edge on the remains of the can, but there is little risk of damage to the die or the bonding wires.Jay_Diddy_B

author: Stonent
author_rank: Super Contributor
timestamp: November 12, 2013, 03:27:06 am
content: Quote from: G7PSK on November 11, 2013, 03:38:47 pmNeat! Thanks! I think I'll have to do some other experiments as well now.

author: c4757p
author_rank: Super Contributor
timestamp: November 12, 2013, 03:31:29 am
content: I'm interested in how they compare to my generic RF transistors I'm sending you.

author: ejeffrey
author_rank: Super Contributor
timestamp: November 12, 2013, 03:33:22 am
content: I have used a can opener like this:http://www.thorlabs.us/newgrouppage9.cfm?objectgroup_id=1830to open photodiode packages, and they claim it works on TO-3. You may be able to find a cheaper version of this type of tool. It works easily and reliably, and generates less metal shavings than a dremel or saw.

author: Stonent
author_rank: Super Contributor
timestamp: November 12, 2013, 03:33:57 am
content: Quote from: Jay_Diddy_B on November 12, 2013, 03:22:52 amI've got a few ideas now on how I'd like to proceed.I thought if there were a small enough pipe cutter I could use that but I don't think I've seen them that small. Since my goal is to open them so I can put a Mica window in them, I could get the very top off and then superglue the piece of Mica to a metal washer and then glue that to the case.I'm hoping to expand on the work done by that one youtube guy (the one that got the huge package of LCD boards from Dave in the contest). I wan to make it look as nice and as clean as possible and if it works, mount it in a sort of wand or probe and come up with some kind of low voltage circuit to respond to the clicks.

author: Stonent
author_rank: Super Contributor
timestamp: November 12, 2013, 03:39:23 am
content: Quote from: ejeffrey on November 12, 2013, 03:33:22 amThat would be perfect if not for the price. Basically what I was thinking of with the pipe cutter, except they're way too bulky.(My previous post was in progress when you posted, but I sent it through anyway to avoid retyping it)

author: vk6zgo
author_rank: Super Contributor
timestamp: November 12, 2013, 04:23:35 am
content: TO-3 packages are tough!As I went to park at work ,I heard 'clink!,clink!,clink! coming from my RH rear tyre.I found a 2n3055 stuck in the tread,with the top pushed in quite badly.Prising it out,I found one leg bent,& the other penetrating the rubber.Luckily it wasn't long enough to cause a leak!I took the transistor inside & tested it---it still worked!

author: Stonent
author_rank: Super Contributor
timestamp: November 12, 2013, 05:08:54 am
content: Quote from: vk6zgo on November 12, 2013, 04:23:35 amBrick dunny so they say?

author: dr_p
author_rank: Frequent Contributor
timestamp: November 12, 2013, 07:10:22 am
content: IQuote from: flolic on November 11, 2013, 12:36:47 pmI tried this last night on my 7812, but with a pair of pliers, and it worked quite nicely.

author: G7PSK
author_rank: Super Contributor
timestamp: November 12, 2013, 03:26:35 pm
content: Quote from: Stonent on November 12, 2013, 03:27:06 amPM me an address so that I can post them.

author: SeanB
author_rank: Super Contributor
timestamp: November 12, 2013, 08:49:19 pm
content: There are some Motorola devices with an aluminium cap that can be peeled off, but most common is a steel cap. The vice ir hacksaw method is normally the best, though if you use a hacksaw blade or a file to make a small cut at the top and then use a set of electrical cutting pliers you are not too attached to you can peel the top off easily enough. wash inside with a solvent ( alcohol or thinners works well) to get the filings out and you can use it.G7PSK if you want to post some of those glass transistors to me I would like them, they will go nicely with the can versions I have.

author: Simon123
author_rank: Regular Contributor
timestamp: November 12, 2013, 08:53:29 pm
content: Quote from: tsmith35 on November 11, 2013, 11:51:37 amProably they were sandwich like chips and the acid-hydrochloric eats cement or what that white stuf is. But it will also eat bond wires.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: November 12, 2013, 09:04:22 pm
content: Quote from: Simon123 on November 12, 2013, 08:53:29 pmNitric acid will not eat the bond wires but will oxidize the plastic very nicely. Most stuff that would eat the steel outside would eat the bond wires inside. I don't have any TO-3's to test it on otherwise I would see how well nitric works on the case. We just got a fresh bottle in at work.

author: Stonent
author_rank: Super Contributor
timestamp: November 12, 2013, 09:09:35 pm
content: TO-3 cases are solid metal. So it probably wouldn't work.