Problem with SM caps

Numbers and grades have NOTHING to do with REAL grasp of the physical realm. A quick viewing of "Goodwill Hunting" should have cleared that up for you.

In other words, I'd bet that you can't shoot pool worth a shit either. And yes, that would also be quite a tell.

Everyone affected will send you their hair replacement bills. :-)

I learned a long time ago that strain relief is important, even in a quick test scenario.

ONLY? My production people would use their fancy combo IR and hot-air thing to remove multi-pin parts. They have a separate setup for reworking BGAs; our only problem is that our BGA (placement error + electrical failure rate) has been precisely zero, so they don't get to play with that rig.

Who are you to decide what's incorrect? What's proper to us is what works. And what they do *does* work. If it displeases you, so much the better.

John

One big tip works fine. The part comes off in a couple of seconds, with no stress on the pads or on the part. Solder wick never gets all the solder from under thepads, so you've got to use force to finally break the part away. If you're lucky, the pad isn't damaged and you just leave a bit of the end-cap plating on the board.

Silly.

John

Now THAT is funny. Hilarious. Physics without numbers!

Pool bores me. I'd rather ski, move my entire body through the air, 40 mph between the trees on a couple of strips of fiberglas, coefficient of friction 0.03, 3000 vertical feet at a run. It's like being an air hockey puck. It's like flying, except when it IS flying. Beats knocking balls around a flat table with a stick.

John

If you solder a sm part vertically, one pad down and one sticking up, it's incredibly fragile. I do that sometimes making copperclad breadboards, and usually break them. Disc ceramics or axial resistors are better for stuff like this.

John

Nothing to tie it to. A 0603 pad was the best solution, though I now use a hunk of 28GA wire and a dab of crazy glue. It gets ugly but the board fix was worse since there was nothing left on the back of the board.

Wrong. What it does is allow the reflow and removal operation you previously described to be done with less heat, and less time on the terminations, an essential operational step. No stress on the pads, thermal or other wise in such a method. Yours works as well, it just isn't that good for the part. UNLESS you get it off the solder tip immediately. Or replace it and pitch the removed part.

Pool was the game of Kings, so I can understand you not being able to do it or grasp it well enough to like it.

I can slalom and barefoot water ski, and I always hit the black diamonds on the ski slopes. Plenty of reasons to say that snow sucks more than indoor sports though.

Wrong. You think that is the figure for a human standing upright? More like the figure for the skis, which essentially is meaningless in real world use. You, however, certainly have a higher coefficient than cars do, so your figure is off by at least an order of magnitude, and I would say far more.

In other words... Jeez, what a lame claim.

It figures that that is all you think it is. Likely a bit more due to the fact that your just plain are not all that dexterous. You probably wouldn't even know the value of a co-linear stroke. You probably will make or immediately think of some lame twit remark about the use of the term 'stroke'. That pretty much sums up your mind set after seeing stupid remarks like that.

A 'tombstoned' part (yes, Johnny that is the right term) is fine. The thing one must do is set up a strain relief such that ANY part mounted on the assembly that you are attaching to receives NO physical strain whatsoever. That means a strain relief downstream to the connection. Pretty much common sense.

Tombstoned parts are actually acceptable assembly processes in the IPC standard that most currently follow. Just not for class 3.

Tack pack does work. The fine gauge wire helps if 'service loops' are used as strain 'springs'. Similar to the way Shockley did it on the first transistor.

I have used a twisted pair of fine hook up wire, twisted tightly enough that they grapple each other well. Then I tie one to the service test point, and the other to an SMD tantalum or other large form factor anchoring pad.

It was an axial resistor that provided the leverage to make a mess. In this case I was trying to inject a test signal into the summing node. All the probes got too heavy, the board moved, and...

But we agreed that we shouldn't reuse the part. I often check them after I pull them, especially caps, to verify their value, and they're always OK. Ceramic caps are manufactured by firing green tape and metal frits, probably at much higher temps than my iron can hit.

It would be interesting to see what temp it actually takes to damage a ceramic cap or a sm resistor.

John

Exactly: pool is a game. Skiing is a sport. I never play games; they are mostly composed of random events and bore me.

John

Stay away from numbers. When you deal with anything quantitative, you are Always Wrong. It was interesting, your comment about physics having nothing to do with numbers. Hint: the coefficient of friction is mostly independent of the applied normal force. In other words, is's in the range 0.03 to 0.05 for the empty skis, or for me standing on the skis. And that determines the deceleration rate gliding on level snow. Which is one reason it's so much fun. Math is fun too.

And I always wear skis when I ski, and keep the bottom parts against the snow. Maybe you do it different.

I'd guess that in a good hockey stop, you could get the coefficient near unity. I'll try to measure that next trip up.

John

John, Are you so isolated you have to feed the troll to engage in conversation ?:-)

...Jim Thompson