After building 4000 PCA's for a customer, which has 14 Case Size "A" Tant. Caps out of approx 400 parts on the wave side, it was found that PCA's averaged 14 "No Solders"/PCA after wave. (50% joints of 28 in random positions) Almost all the defects were on these Case Size "A" component types. Case size "D" Tant Caps and 805 ceramic parts were defect free. What is unique about Tant SM caps is that the leads only travel half-way up the body , unlike ceramic chips which terminal surround the ends. The Case size "D" had larger lands. Occasionally defects for excess solder were found as a result of trying to increase the solder flow to these difficult parts. (eg slower feed rate, higher chip wave etc. The SOLTEC wave soldering machine uses a foam fluxer (No Clean flux) with good foam height and bubble size. An experiment to hand spray flux reduced the qty of defects to 4/PCA, but did not make the process defect-free. (Yes we know foamers are not the best kind) To make the process Defect-Free and specifically free of "No Solder" joints, we measured a sample of exposed solder lands and checked a variety OK and "bad (NS)" joints. The result was there were 0 joints with 0.060 (1.5mm) exposed lands that failed. Since it was too late to change the pad design for this production run, we considered 1) do nothing except continued 100% inspection, 2) hand-solder both ends, 3) offset the part, leaving only one joint requiring hand solder. This was considered better than leaving inspection to chance. To offset the parts 0.5mm or 20 mil on the Fuji placement offset, would provide 100% probability of lead soldering . The pad size allows contact with the 0.8mm (32mil) terminal length with the offset and then manual soldering of only 1 joint is required. This is expected to reduce the process variable of Case Size lead solderability to zero and make this part of the process defect-free. Other Opportunities ==================== Interesting enough we theorize this solution will fix SOT-23 "No solder" problems. I've read the history of people who have had problems on this part. If you can, increase the land size to accomodate your wave soldering process or in the Size "A" Tant Case here .060" or 1.5mm. Don't put too much faith into IPC-782 design requirements. They are only guidelines. Determine your own optimum LAND Designs and provide input to your customer's design. EXPERIMENTAL DATA Exposed Lands Inspected Joints to IPC class2 [thou] [mm] % bad % OK ====== ===== ===== ===== 0.000 0.00 100% 0% 0.010 0.40 100% 0% 0.020 0.80 50% 50% 0.030 1.20 50% 50% worst case 0.040 1.60 33% 67% this is IPC782 guideline size 0.050 2.00 43% 57% 0.060 2.40 0% 100% defect free on several batches inspected 0.070 2.80 0% 100% 0.018 0.73 Kemet MIN. Land Length Case size "A" Tant Caps 0.031 1.23 Kemet NOM. Land Length Note that KEMET does not have a MAX!! 0.040" 1 IPC782A MAX Land Length (calculated) Haven't checked Rev B yet 0.060 1.5 mm C-MAC MIN Land Length for No clean flux with foam fluxer on SOLTEC wave RSVP by e-mail regards, Tony Eng Manager Web: http://cmac.ca *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************