How to solder this chip in properly?
nms
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#1
25th February 2012
Old 25th February 2012
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How to solder this chip in properly?

I removed the old chip and cleaned up the area with wick and methyl hydrate.. now I need to solder in the new chip. It's a voltage regulator for my Motu 828mk2.

It has a metal tab underneath though that solders to a little heatsink under it. How do I correctly go about installing this? Tin both sides where the heatsink and contact point on the chip meet then attach and heat up the tab til the solder melts between them and bonds? Any caution needed with amount of solder used?

http://www.futureelectronics.com/en/...?IM=0&IT=False
nms
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25th February 2012
Old 25th February 2012
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#3
25th February 2012
Old 25th February 2012
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Clean the pads flat with Solder-Wick.

1: Put the part in place, holding with tweezers and line it up on the pads, then line it up for all connections as best as you can, then solder the easiest down firmly.

2: Push the heatsink part or the part down with a bit of pressure, solder the tab
with enough solder to make a nice, light, even flow of solder.

3: Solder the remaining leads.
nms
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#4
25th February 2012
Old 25th February 2012
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So I wouldn't be trying to solder the heatsink on the board to the metal square under the center of the chip? No thermal compound used for this sort of thing either?
#5
25th February 2012
Old 25th February 2012
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If the part removed shows it was previously soldered, then I'd solder it.

I'd probably solder it anyway in this case, because it looks like it produces a lot of heat.

you might need to have your iron hot for this one, the heatsinking will suck the heat right off your iron quickly. maybe warm the contacts a little first. with a little bit of iron heat.

tinning the part shouldn't be a bad idea. it will also warm it up.
#6
25th February 2012
Old 25th February 2012
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+1 to what Dan says. Only thing I would add is with a surface mount part like this, some no-clean paste flux makes everything easier. DO NOT pre-tin the part, as SMD is always easier if the parts fit flush to the board prior to soldering. No thermal compound is required as the tab is making a direct thermal connection to the board through being soldered to it. You should be able to find all sorts of SMD soldering tutorials on-line.
Best,
Ike
#7
25th February 2012
Old 25th February 2012
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Quote:
Originally Posted by Muser View Post
tinning the part shouldn't be a bad idea. it will also warm it up.
Absolutely the worst thing you can do..no need,

The reflow flux paste is an *absolute* for good smd replacement.
As Ike has already stated.
Only "bolted or screwed" power devices need a thermal paste (with insulate,and/or silicone gasket)...
Smd power devices have the tag soldered to the pcb pad for heatsinking as per design.
nms
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#8
25th February 2012
Old 25th February 2012
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I only ever solder once in a blue moon so I don't have solder paste or flux unfortunately. It's just one little chip though so hoping I can get the job done with just an iron and your typical rosin core solder.
#9
25th February 2012
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by the sounds of it, I'd get some reflow flux paste. if it's mentioned as a must, I'd head the warning.
nms
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#10
25th February 2012
Old 25th February 2012
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Quote:
Originally Posted by Muser View Post
by the sounds of it, I'd get some reflow flux paste. if it's mentioned as a must, I'd head the warning.
I can't use paste with an iron though and don't have hot air as an option.
#11
26th February 2012
Old 26th February 2012
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Quote:
Originally Posted by nms View Post
I can't use paste with an iron though and don't have hot air as an option.
ahh yes. your right. I have (paste) but no Airgun.

I should try and get one at some point. things like this make realize I'm going to need it if I want to keep my equipment running long into the future.
nms
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#12
26th February 2012
Old 26th February 2012
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Aha!

Well, I needed to get this dealt with and wasn't into taking more downtime so I made it happen with what I have.

I put solder on the underside of the chip where it connects with the heatsink and some on the tab as well.. making sure it was all connected.. hoping that when I went to bond the chip to heatsink I could heat the tab to melt the solder straight through to the inaccessible center part. Seems to have worked like a charm. I checked the test point and am getting a steady 3.285v for this 3.3v tp which is good yes?

Also, just to check.. When you have chips marked LM1117DT or LM1117DTX they are both the same chip right? The last part is just for type of distribution packaging for ordering purposes?
#13
26th February 2012
Old 26th February 2012
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You don't need an air gun to solder a chip that size just relow paste,
and a decent iron.......!!
The Technique is something you have to learn
#14
26th February 2012
Old 26th February 2012
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I guess I'll get some dead electronics at some point and practice.

These things seem to go on Motus. I think I saw one on a MTP AV go out too, in another thread.
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