[ATM] soldering SMPs

[Pat Bunn]

Does the flux that is between the solder pads need to be wiped off - is it 
conductive? When you place the paste on the pads - it would get between 
pads - is that OK?

I am getting read to solder a very small DSP chip and am trying to figure 
out how not to ruin it.

Pat Bunn
----- Original Message ----- 
From: "Richard" <cnc at cncservo.co.uk>
To: "Dominic-Luc Webb" <atm at atmlist.net>
Sent: Thursday, December 13, 2007 10:42 AM
Subject: Re: [ATM] soldering SMPs


> Hi Dominic-Luc,
>
> Thursday, December 13, 2007, 3:20:04 PM, you wrote:
>
> DLW> Anyone here have experience with soldering very small SMP
> DLW> devices? Solder points are 1.5 mm apart.
>
> Yes, a little, but I can assure you that 1.5mm pitch is not "very
> little". Try the 0.5mm pitch devices ;)
>
> You can use a hot air gun, but I have been OK with a new temperature
> controlled bit. The one thing that is essential though is solder
> paste, which is a paste of fine solder particles in flux. In
> production it is silk screened onto the PCB, but you can get away with
> wiping a line of it along the line of PCB mounting points, mounting
> the device carefully in place, then either running an iron along the
> top of a row of legs or reflowing with a hot air gun. The flux seems
> to mostly stop shorts, but if you do get a short between pins don't try
> to piggle it away, but just heat and wipe away the solder, apply new
> paste and try again. It's a bit of a pain by hand but you can mount
> 100+ pin devices on sub 1mm pitch in about 5 to 15 minutes. The paste
> I've had success with is made by Kester and is -325/+500 mesh, 63/37
> Tin/Lead, although Lead bearing alloys are outlawed most places now.
> You can find it on Ebay sometimes.
>
> -- 
>
> Best regards,
>  Richard in the UK
>
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