Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Phil Hobbs Newsgroups: sci.electronics.design Subject: Re: Feedthough/via that straddles (i.e., is bisected by) the cut edge of a PCB? Date: Fri, 31 May 2024 12:45:21 -0000 (UTC) Organization: A noiseless patient Spider Lines: 92 Message-ID: References: <66737zu9zeai.1ih823p78yo32.dlg@40tude.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Fri, 31 May 2024 14:45:22 +0200 (CEST) Injection-Info: dont-email.me; posting-host="6aed9beae5fe603b36263e7f17f2e961"; logging-data="2354653"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18GMtfnJ1fVoCsTbd0MvJK2" User-Agent: NewsTap/5.5 (iPhone/iPod Touch) Cancel-Lock: sha1:06WtTbT8KyiEKPdChTM4j1rOxmg= sha1:3gBj+xKAwtjE0THDLTDw12A7qkI= Bytes: 4826 Don Y wrote: > On 5/30/2024 10:26 PM, Jasen Betts wrote: >> On 2024-05-29, Don Y wrote: >>> On 5/29/2024 6:20 AM, dalai lamah wrote: >>>> The keyword to look for is "castellated holes". The easier way to do it is >>>> to find a manufacturer that explicitly supports them, and follow their >>>> instructions. For example: >>>> >>>> https://www.pcbway.com/pcb_prototype/What_are_Plated_Half_Holes_Castellated_Holes_.html >>> >>> Excellent! /Grazie tante/ >>> >>> A first pass through the description doesn't seem to EXPLICITLY say it but >>> it seems like they are implying that the drilling occurs ON the edge, and not >>> before milling? I.e., each drilling action results in ONE such "hole" -- not >>> two HALF holes (on adjoining panelized boards) >> >> Usually the cutting is with a 2mm router and the holes are much >> smaller than that. so afterwards you only get one half of each hole. >> >> I suppose you could do vee groove instead of routing but I'd worry aboout the >> copper tearing when the boards are separated. (or maybe the copper >> would damage or contaminate the saw so they refuse this) >> >> as I unserstand it they are drilled at the same time as other plated >> holes and slots and then after plating, etching, and mask the edges are cut. >> >>> >>> "...BEGINS with drilling ON the edge of the substrate..." (emphasis mine) >> >> I'm pretty sure they mean egde of your board outline. > > > From the previously cited URL (reformatted for clarity): > > "The traditional process for manufacturing plated half-holes typically > involves the following steps: > - drilling > - applying chemical copper to the panel > - image transfer > - pattern plating > - film stripping > - etching > - solder mask layer printing > - surface treatment > - hole formation > - contour milling. > > However, the above steps can result in decreased productivity and > performance of the product." > > I would assume milling the already plated hole being the problem. > > "Nowadays, the process of forming plated half-holes differs from > the usual traditional methods. > > The process of forming plated half-holes begins with drilling > /on the edge of the substrate/. > > Suggesting that the drill actually is on the physical edge of the > material, not an edge that will be created after milling. > > "Therefore, it is crucial to use /specialized drilling equipment/ > as any deficiencies in the equipment can affect all subsequent steps. > > Again, I would assume this is required because there will be a bending > moment applied to the drill bit as it encounters material only on one > "side" of the bit. I.e., that it will want to bore a hole that is not > completely orthogonal to the board as it bends further from the intended > hole centerline as it proceeds further through the material. > > Once the preparation is completed, the next step is copper plating > of the holes. Copper plating is equally essential as it ensures good > conductivity for the components on the circuit board. > > Note that they don't mention "specialized MILLING equipment" (to preserve > already plated holes with extra care) > > ? > > That process wouldn’t leave copper hackles behind, so it obviously isn’t universal. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics