Hi Bev,
Thanks for the quick reply and inputs.
The product that I've written is built to IPC-6012, Class B.
Best Regards,
U.Nagaraj
> Uppina,
> Wow! LOTS of questions. I can only answer some.
>
> 1) Yes, generally ENIG boards store better than HASL boards. HASL board
> solderability decreases because of growth of oxide and growth of
> intermetallic. If the HASL layer is thin the intermetallic can reach the
> surface sooner and then, well, it ain't going to solder.
>
> Vacuum packing can increase the shelf life of finishes that can oxidize.
> This assumes excellent packaging, not stored so long there are
> intermetallic problems, etc., etc.
>
> For a lot more on this get the IPC series of docs on surface finishes. I
> can't remember the numbers, but I am sure someone else will respond with
> those.
>
> 2) Photos to TechNet get stripped out. Either sent to Steve Gregory or
> post on the IPC site.
> Question to you: what IPC class of product are you building?
>
> Bev
> RIM
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Uppina Nagaraj
> Sent: Thursday, June 17, 2010 7:30 AM
> To: [log in to unmask]
> Subject: [TN] Query on shelf life of PCBs & impact on solderability
>
> Dear All,
>
> I have 3 queries in all.....
>
> 1. One of our customer has changed the surface finish from HASL
> to ENIG. Their main reason for this change was that they
> have had a bad experience with storage of HASL finished boards
> (the reason for which is not shared with us). They had encountered
> solderability problems on the HASL finished board which they
> had stored for a period of time.
>
> Their expectation with Gold plated surface is the storage
> of the PCBs can be for a longer period of time as compared to
> HASL finish.
>
> Initially they had a requirement for 1micron thick electrolytic gold,
> but later on they changed the requirement for an ENIG process with
> gold around 0.05 to 0.10 microns.
>
> Now my question......
>
> Is there any guideline on the shelf life of the PCBs (with regard to
> solderability) of the following surface finishes....
>
> a) ENIG
> b) HASL
> c) Immersion Tin
> d) Electrolytic Ni and electrolytic gold with Gold thickness
> of 1.0microns
>
> Will vacuum packing help to extend the shelf life?
>
> 2. One of our customer is doing hand soldering of PCBs with ENIG finish.
> They're inserting a strand of tinned Copper wires from component side
> and later on using soldering iron to do the soldering from the solder
> side.
>
> The solder is able to flow up from solder side to component side, but
> the solder is unable to complete wet the pad on the component side.
>
> I've attached the photos of example of the phenomenon. These photos are
> without the wire, I've just used bare PCBs to do the soldering to
> illustrate the phenomenon.
>
>
> Now my question....
>
> a) Will increasing the volume of the solder help in complete wetting
> of the pads on the component side?
> b) Any other way to get a full coverage on the pads on the component
> side.
>
> 3. This question is about the same customer which I've mentioned in
> para 2 above, is doing hand soldering. In one of the stage of
> component assembly, they're (hand) soldering a flexible PCB
> on the ENIG finished rigid PCBs.
>
> They have a unique practice during this stage of soldering. They've
> explained to us that this particular component is very sensitive to
> high temperature and hence the soldering iron temperature is set at
> 210Deg C. They're using Sn60/Pb40 solder for this soldering operation.
> After the soldering iron achieves 210Deg C, they're turning off the
> power to the soldering iron and doing the soldering of the flexi PCB
> onto the rigi PCBs. We'll not know the actual
> soldering iron temperature at the point of contact.
>
> They've complained to us that the soldering is poor.
>
> We know that the melting temperature of solder is around 183deg C. But,
>
> is there any guideline on the minimum temperature for soldering to get
> a good flow of solder and completely wetted solder?
>
> Thanks for your inputs in advance.
>
> Best Regards,
> U.Nagaraj
> MICROPACK Ltd,
> Bangalore, INDIA.
>
>
>
>
>
>
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