Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


QFP Shifting / Solderability Issue

Views: 4489


aj

#50401

QFP Shifting / Solderability Issue | 28 May, 2007

Hi All,

We have a QFP device that is struggling to achieve acceptable solder joints. I have noticed one or two of the components shifting during reflow. I can adjust the Blowers but I dont have any issues on other boards.

This seems to be a straight forward issue with the device not soldering.

I suppose I am just looking for some feedback on anyone elses experiences with this sort of issue.

thks

aj...

reply »

#50402

QFP Shifting / Solderability Issue | 28 May, 2007

Good afternoon,

Have you checked placement accuracy? Is it installed without shift prior to reflow? Are you sure it shifts in the oven? I believe tension cannot cause QFP shift since QFP has quite low self centering ability. Such kinds of shifts are usually caused by mechanical problems in the oven or placement issues. Could you give more details?

BR, Pavel

reply »


aj

#50403

QFP Shifting / Solderability Issue | 28 May, 2007

Placement is fine...

There are other fine pitch components on the board which are fine.

It is a 2up panel - one will be fine and the other might be shifted. Alternates between boards.

aj...

reply »

#50413

QFP Shifting / Solderability Issue | 29 May, 2007

Is the component solderable per ANSI/J-STD-002, Solderability Tests for Component Leads, Terminations, Lugs, Terminals, and Wires?

reply »


aj

#50414

QFP Shifting / Solderability Issue | 29 May, 2007

Hi Dave,

The customer is supplying a new batch as this batch just doesnt want to solder.

aj...

reply »

#50470

QFP Shifting / Solderability Issue | 31 May, 2007

We place a QFP 256 leads 20 mil pitch, had a lot of troubles with shifted components and solderability issues. solderability is not a problem anymore; we solved with a ramp-to-spike profile with .9�C/s 'til 183� then spike to about 118�C, TAL ~60s. We're using indium nc-smq 92J. Shifted still being an issue; but is machine related (IP3) we cannot obtain repeatability.

reply »

#50480

QFP Shifting / Solderability Issue | 1 June, 2007

Hi Aj, What type of QFP are we talking about? We had in the past big problem with QFP-304 0.5mm pitch from ALTERA. Similar as you describe. Note. No problem with QFP-256 or QFP-196 0.5mm pitch, or anytying less than -304:s

Can You be a little bit more specific about your problem? Best Regards, Mika

reply »

#50481

QFP Shifting / Solderability Issue | 1 June, 2007

These ones from ALTERA the QFFP-304 0.5mm weight: 32gr. used to give us a really headache in the past. Not only soldering issue:s but also the placement in x-y-theta! The stencil thickness of ours is 0.13mm and because of ohter compomponent packages, we couldn't replace this according to just this particular comoponent.

If you also are facing a coplanarity/coliniarity problem like we did, then you are @�$%...Big time!!! No more than 0.15mm.

We are using the UIC GSM1 with a 340F nozzle (hey we have tried all type of nozzles; including 360F specially made 380F) but we still got some problem. Please let us know yours... One thing though; in the comoponent library for GSM: Make sure that you are using the right vision value, since the "blue cross" in the vision inspection will target on different spots on the leads; which in turn will cause the component to shift during the placement!!

To be able to see this on the vision monitor - go in to the system setup and change the diagnostic value to 5 or at least 4 (temporarly until yo solve your problem - this will significally slow down the machine). And watch where the blue cross is located on each lead tips in step mode, because it uses this info later on when the vision algorithm calculates how to compensate for the mis-pick! Lead inspection (in the component database) must be turned off to be able to see those blue cross during the investigigation, preferable in step mode. Make sure that you save your program and reload. A good practice is to make any changes in a copy of the component database & the program. Just in case... The GSM will (depepending on model) also use another vision algoritm if you choose to go for vision inspection C in the component library but it is less accuracy while it could provide more placement effiency. This might help. Also try to turn on lead inspection and set at least one value there; for. ex 0.125 mm. for lead bend (I don't recall what the name is in the component database, but you will find out). Zeroes means that it will use a standard vaule depending in what category you are dealing with or I just nean that that type of inspection is turned off.

Now, you could face an increase number of vision rejects because of this lead inspection option turned on, but if you have set the numbers correct, it will save you the money in a long term....I think the single most important option in this category is the check for lead bend of fine pitch comps. This will also cause anotother vision algoritm to take place whitin the database QFP-category (execept for the new lantern vision system located in the VME-chassi), again depending on which GSM-model & UPS s/w /Vision executive you are using.

Question: How old are the components of yours, since this will directly cause wetting problem during reflow soldering process? /Mika

reply »

#50482

QFP Shifting / Solderability Issue | 2 June, 2007

I almost forgot; If the pcb have HASL (Non RoHS) surface finish, then big fine pitch QFP:s could be shifted during reflow, beacuse of the un-even pad-surface... We have been trough that scenario also... But step No.1 is to make sure that the component is placed ok. We use dubble sided sticky tape to verify the placement. And to verify the placement accuracy & repeatability you must run several components, otherwise it is worthless as explained in my previous posting...

Make sure that the paste deposit registration is 100%. Pcb with HASL and not 100% paste registration on pad, is to ask for fine pitch QFP problem. /Sincerly

reply »


aj

#50507

QFP Shifting / Solderability Issue | 5 June, 2007

Hi all,

Just to close off this issue I was having - the customer supplied a new batch of components and there was no issues .

Looks like the whole of the previous batch was effected with solderability problems.

Thanks for all the replies.

aj...

reply »

PCB X-Ray Inspection System

ii-feed SMD Intelligent Feeder