No registration or passwords; no pop-up ads -- just aloha, fun, & answers.
(as an eBay Partner & Amazon Affiliate earns from qualifying purchases).
Home /
T.O.C.
Fun
FAQs
Good
Books
Ref.
Libr.
Advertise
 
Help
Wanted
Current
Q&A's
Site 🔍
Search
pub  Where the
world gathers for metal finishing
Q&As since 1989



-----

Unfilled PTHs during wave soldering




I have a problem with wave soldering on some boards. We have some holes on the boards which just cannot fill the via PTHs. Affected holes are random and the holes are completely unfilled (see thru'). Wetting is observed on the annular rings (top and bottom). Need to know what are the potential root causes. All variables and parameters are unchanged(flux, type of solder,etc) , and this problem only appeared in the last several days while we have run this for a very long time.

Yip Chee Keen
electronics mfgr - Singapore
2004



Sounds like contamination in the holes, perhaps from the board plating or hole drilling. Or possibly your flux bath has changed viscosity due to evaporation.

If the problem only shows up on holes that have component leads in them, it's usually because the leads are too big for the hole. Or possibly dirty component leads.

If it's not component leads, you need to look in the unfilled holes. You can try viewing with a microscope using bottom illumination slightly to the side of the hole. Or use a borescope if you can get one. As a last resort, cut the board in two through one of the holes using a fine diamond saw. Then you can use a microscope to see what is going on.

If you see board material where the hole plating should be, that's either a drilling or plating problem. A drill that is not sharp or too fast a drill feed rate can leave surfaces that won't plate.

If you see contamination (usually gray or black) in the hole, the boards may have been in storage long enough to collect dirt. Clean with BOTH an ionic cleaner (detergent & water), AND then with a degreaser solvent.

The fourth possibility is flux not getting in the hole. Visual inspection immediately after wave soldering, before washing or lead trimming, may spot this.

Tom Gallant
- Long Beach, California
2004




(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

 
Jobshops
Capital
Equipment
Chemicals &
Consumables
Consult'g, Train'g
& Software


About/Contact  -  Privacy Policy  -  ©1995-2024 finishing.com, Pine Beach, New Jersey, USA  -  about "affil links"