Carl
Comments are:
* We prefer probing solder, rather than copper. Softer material, longer
probe life, bla, bla, bla.
* So, we don't probe OSP. The problems probing OSP must be similar to
probing low-res fluxes and RMA. There's no free lunch. In this case,
consider performing PM on your probes.
* Our probe maintenance techs, ex-test equipment operators, think flux
residues are a pain in the gluteus maximus. When a fixture begins to
act-up, they:
- Dry run the fixture to improve contact. If probe tubes are unused for
long periods of time, electrical resistance may be initially high until the
wiping action of the plunger clears the oxide / crud layer.
- Dry scrub probe tips with a wire brush (like Techni-Tool 872M1034, but
with longer rows of bristles). Messy business. Run a shop-vac while
scrubbing. [Sooner, rather than later, we'll set-up a hit-based scrub
schedule that can be done off-line.]
- Inspect the probe side surfaces for corrosion / flux res that turn
gold black colored and prevent good contact.
- Change probes (from a collection of different tip types: crown,
straight point, diamond) to hopefully select (tailor) the correct probe for
the probe location. They chart probe changes. Currently, we buy a lot of
straight blade probes. Diamond pin are the second choice.
- Change probes roughly according to hits, using the probe manufacturer
recommended change-out schedule ... 50k hits or something like that.
* We see a reduction in false probing according to pad area. IPC-SM-782
contains statistics on falses versus pad size. Obviously, square pads
further reduce false probing.
* Regardless of the flux type, recognize that flux selection is the biggest
driver to this issue.
* Finally, if you clean these flux residues, a large portion of this problem
goes away.
Dave Fish
----- Original Message -----
From: "Carlr Ray" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, August 14, 2003 12:15 PM
Subject: [TN] Entek and Test Probes
> Hello All,
> I have a question about Entek and preferred types of probes for ICT
> Testing?
> Also I have an issue where we are discussing the need to solder test
> pads or leave them unsoldered. Currently we are experiencing several ICT
> problems with solder test pads. We have deflected test probes, excess
> flux contamination and a high amount of false failures. We are using
> No-Clean Paste.
> As usual any feedback is appreciated.
>
> Carl Ray
> Sr. Manufacturing Engineer
> Huntsville, AL 35807
> Phone: 256-882-4800 ext. 8845
> Cell: 256-990-1990
>
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