-
- News
- Books
Featured Books
- smt007 Magazine
Latest Issues
Current IssueBox Build
One trend is to add box build and final assembly to your product offering. In this issue, we explore the opportunities and risks of adding system assembly to your service portfolio.
IPC APEX EXPO 2024 Pre-show
This month’s issue devotes its pages to a comprehensive preview of the IPC APEX EXPO 2024 event. Whether your role is technical or business, if you're new-to-the-industry or seasoned veteran, you'll find value throughout this program.
Boost Your Sales
Every part of your business can be evaluated as a process, including your sales funnel. Optimizing your selling process requires a coordinated effort between marketing and sales. In this issue, industry experts in marketing and sales offer their best advice on how to boost your sales efforts.
- Articles
- Columns
Search Console
- Links
- Events
||| MENU - smt007 Magazine
Ask and Answer -- October 16, 2002
December 31, 1969 |Estimated reading time: 3 minutes
Ask and Answer is a forum where SMT professionals with questions can meet up with those with the answers. If you know the answers to any of the questions below, or have questions of your own, please e-mail them to christinef@pennwell.com, referencing the reference number below each question, and we will publish them in a future column. Please include your name and the location you are writing from. SMT Online reserves the right to edit responses. Look for Ask and Answer every Wednesday.
QUESTIONSMike Bywater writes: Is it really worth going lead free? The impact on the environment for mining, refining, processing waste disposal and cleaning appears from current reports to be greater than the impact of small percentage of lead output going in to landfill. Has everyone missed the point of reducing the burden on the environment as a whole? Reference Number: 101601
George Lucas writes: Are surface mount metal film resistors and diodes susceptible to cracking like surface mount multilayer ceramic capacitors and what would be the expected failure modes for a cracked surface mount metal film resistor when exposed to a high humidity environment? Reference Number: 101602
Cheryl Johnson writes: I am getting ready to do my first flip chip on flex design and need to know if there is any good reference material I can use to find out the following (or if someone can just tell me the rules of thumb!): 1) "Balls" are ~3 mils as close as 7 mil center to center. 2) What size pad (1:1?) do I put on my copper layer? 3) Soldermask vs coverlay -- and what kind of openings for each? 4) Can traces be 3-4 mils as well? 5) What kind of notes would be different from standard flex? 6) Would anyone have a sample fab/gerber file set (even in pdf) that they could show me? Thank you. Reference Number: 101603
John Noel Villordon of China writes: I am working in an EMS company that manufactures electronic products and assemblies using surface mount technology. I would like to know how long a time can a standard SMA PCB/PCBA (thickness equal to 1 mm) be exposed in ambient/normal manufacturing temperature (21 to 24 degrees C) & humidity (40 to 60 RH) such that the accumulated moisture is still negligible? What is the moisture sensitivity JEDEC level of a standard double-sided SMA PCB? Thank you. Reference Number: 101604
Ruud Lobel of the Netherlands writes: Is there any rule of thumb or another way to know what is the ideal plated through-hole diameter vs. PCB thickness when trying to fill the holes with solder? I need this for improving the thermal conduction below a power device. What's best: applying solder (paste) to the holes, reflow and mount the SMD afterwards or do(ing) this in one single pass? Or are there other low-cost solutions that can be used instead of solder filled vias? Thank you. Reference Number: 101605
Les Pearson of California, Md., writes: I work for a company that repairs a RF test set for the Department of Defense. Essentially the unit is made up of 24 RF submodules. Each submodule has several hybrid ceramic substrates with gold print and SMT components on top. The bottom surface is glued in a shallow aluminum block cavity using conductive epoxy. Removal of the substrate for rework is difficult, expensive and time consuming. In trying to rework the substrate while attached to the aluminum block, I am unable to apply enough localized heat to effectively cause solder to flow before the heat rapidly dissipates.
Is there any new technology, technique, ideas that might help resolve my problem? Any help would be greatly appreciated. Thank you. Reference Number: 101606
Gabe Cherian of Sun Valley, Idaho, writes: My question is about the "standards" for solder pads on PCBs to accept BGAs and similar packages, and the solder pads on the BGAs themselves or the other packages. I know that BGAs dimensions and the solder balls attached to them are covered by JEDEC standards. For example, JEDEC Standard # MO-156 covers the "Square Ceramic BGA Family 1.00, 1.27 and 1.5 mm pitch," which JEDEC designates as CBGA-B. I can get the JEDEC Standards through the JEDEC Web site. However, these standards do not give all the answers that I am looking for.
I would like to know what are the diameters of the solder pads on the BGAs (ball grid array packages) and on the PCBs (printed circuit boards) that would accept those BGAs. And that goes for all the various kinds of BGAs and similar packages. Also, if some of these packages have pads that are not circular, then I would like to know the dimensions of such pads as well. I would appreciate it if someone can lead me to the source of that kind of information. Thank you in advance for your help. Reference Number: 101607